ELEMENTS
OF
PHYSIOLOGY.
IN TWO VOLUMES.



Elements  of Physiology;
BY
JO. FRED. BLUMENBACH, M.D.
PROFESSOR OF MEDICINE IN ORDINARY AT GOETTINGBN,
MEMBER OF THE  ROYAL SOCIETY OF SCIENCES AT
GOETTINGEN, AND OF SEVERAL OTHER SOCIETIES IN
DIFFERENT PARTS OF EUROPE.
Translated from the Original Latin,
AND
INTERSPERSED WITH OCCASIONAL NOTES.
By CHARLES  CALDWELL.
TO WHICH IS SUBJOINED, BY THE TRANSLATOR,
An APPENDIX,
EXHIBITING A BRIEF AND COMPENDIOUS VIEW
OF THE EXISTING DISCOVERIES
Relative to the Subject of
ANIMAL ELECTRICITY.
VOLUME  I.
PHILADELPHIA,
PRINTED BY THOMAS DOBSON,
AT THE STONE-HOUSE, No 41, SOUTH SECOND-STREET.
M.DCC.XCV. 



TO
THE  PROFESSORS
OF THE
VARIOUS BRANCHES OF MEDICAL SCIENCE
IN THE UNIVERSITY OF PENNSYLVANIA.
GENTLEMEN,
LONG have you been my
fathers and long my attentive pre-
ceptors, in the interesting science
of medicine. You justly hold on
me, therefore, a twofold claim for
the twofold duty of a pupil and  a
son. In respectful acknowledge-
ment of this undeniable claim,  I
now step forward and thus publicly
solicit your acceptance of the first
fruits  of that medical  education,
which you yourselves were pleased
to

vi. DEDICATION.
to patronize and direct with such
ability and care.
Avowedly to solicit an extension
of your immediate patronage and
protection to the following trans-
lation, would be to offer you an
indignity little short of actual in-
sult. Such a solicitation would
falsely represent you as men un-
willing to become the spontaneous
guardians and friends of silent,
unassuming truth and merit, but
standing with open arms for the
reception even of intrusive error
itself, when ushered to your notice
by a brazen front and a blanditious
tongue.
The original work of Professor
Blumenbach has been already sanc-
tioned 

DEDICATION. vii. 
tioned by the applauding voice of
the learned and the ingenious in
almost every part of the globe to
which physical science has hitherto
found its way. On the solitary
basis of its own intrinsic merit let
my translation also stand; or if,
indeed, it be destitute of such basis,
with disgrace let it sink into that
sea of oblivion which so justly
awaits its final reception.
From you, Gentlemen, it is se-
cure of at least, a patient, and, I
flatter myself, an impartial exami-
nation. Should the execution of
the work fortunately meet with
your approbation and applause,
you will be its auspicious announ-
cers to the medical public: but
should it appear to you faulty and
even

viii. DEDICATION.
even wholly unworthy of further
attention or regard, you will not,
I am sure, lose sight of that fa-
vourite maxim of the humane and
generous bosom, " primum pecca-
tum veniandum est"
Impressed with the most pro-
found sentiments of esteem and
gratitude for your favours of a
public nature, as well as for your
attentive acts of private friendship,
I have the honour to be,
Your sincere Friend,
And Pupil,
The TRANSLATOR.
Philadelphia, }
February 11, 1795. }

Preface by the Translator.
WHAT a fashionable letter of in-
troduction is to its bearer, a fashionable pre-
face is to the literary performance which it
openly announces to the world. The former
procures, for the most part, admission, and,
at least, a dinner ; the latter most commonly
an attentive perusal. For their future conti-
nuance, however, in favour and esteem, both
the visitant and the volume must depend on
something more substantial, and of more un-
equivocal utility, than either the light eti-
quette of a letter, or the specious proposals
of a recommendatory preface.
The 

x PREFACE.
The reader is requested to view the pre-
sent presatory address as a mere peace-offering,
made by the translator to ancient and invete-
rate custom, and not as a solemn appeal to the
public designed to enhance either the merit of
the following performance, or the uprightness
of the motives which led to its execution. For
with regard to the merit of the work, I flatter
myself that no character of literature and ta-
lents will ever resign his right of judging for
himself; and as to the motives by which I
was induced to engage in its translation, they
are indeed at present nothing better than ab-
solute non-entities, and will in no way effect
its utility to man.
The want of a new and complete system
of physiology has been long and very sensi-
bly experienced and regretted by all medical
students on this side the Atlantic. As to
myself, I am sure I was led most devoutly to
regret 

PREFACE. xi
regret such a want, throughout every stage
of my medical studies. In order to acquire
a knowledge of the improvements which had
lately taken place in this important branch
of physical science, I was obliged to range
with an infinitude of labour and attention,
through daily accumulating volumes, which
it was sometimes extremely difficult to pro-
cure. This difficulty was augmented even
to impossibility itself with those unfor-
tunately living out of the sphere of public
libraries.
The mutilated abridgment of Haller's
physiology, published in the English lan-
guage, is (to life a common mode of expres-
sion) certainly nothing more than a bare apo-
logy for a system. It is imperfect, erro-
neous, and, in many places, to me wholly
unintelligible. In some parts, therefore, it
no doubt inculcates truth, in others implants
the 

xii PREFACE.
the seeds of error, and in other places again
leaves the young mind at liberty to indulge
itself in all the wildness and revelry of con-
jecture.
For these deficiencies and faults, I am sure
that at least some compensation is made, and
some degree of remedy provided in the fol-
lowing sheets, which I am about to usher
forth to the world. But on this subject let
decision be awarded, and judgment pro-
nounced, by the candid and intelligent rea-
der, and not by
His obedient humble Servant,
The TRANSLATOR. 

CONTENTS.
VOLUME I.
SECTION. I. Of the living Human Body in general 1
Sect. II. Of the Fluids of the Human Body in
general, and of the Blood in particular - 3
Sect. III. Of the Solids of the Human Body in
general, but particularly of the Cellular Mem-
brane . 18
Sect. IV. Of the Vital Energies in general, but par-
ticularly of Contractility . 31
Sect. V. Of Sound Health, and of the Nature of
Man . 39
Sect. VI. Of the Motion of the Blood in general 48
Sect. VII. Of the Arteries . 54
Sect. VIII. Of the Veins which carry Blood. 62
Sect. IX. Of the Heart . 66
Sect. X. Of the Powers by which the Blood is
kept in Motion . 83
Sect. XI. Of Respiration and its Primary Use 97
Sect. 

xiv CONTENTS.
Sect. XII. Of Voice and Speech . 110
Sect. XIII. Of Animal Heat. . 119
Sect. XIV. Of Cutaneous Perspiration. . 126
Sect. XV. Of the Sensorium and Nerves . 142
Sect. XVI. Of the Functions of the Nervous System
in general . 154
Sect. XVII. Of the External Senses in general, but
particularly of the Touch . 162
Sect. XVIII. Of the Taste . 166
Sect. XIX. Of Smelling . 169
Sect XX. Of Hearing . 173
Sect. XXI. Of Vision . 178
Sect. XXII. Of the Internal Senses and other Facul-
ties of the Mind . 195
Sect. XXIII. Of those Actions of the Body which
are subject to the power of the Will . 201
Sect. XXIV. Of Muscular Motion. . 207
Sect. XXV. Of Sleep. . 223
Sect. XXV. Of Sleep. . 223
VOLUME 

CONTENTS. xv
VOLUME II.
Sect. XXVI. Of Food, and the Appetite for it 1
Sect. XXVII. Of Mastication and Deglutition 8
Sect. XXVIII. Of Digestion . 16
Sect. XXX. Of the Bile . 28
Sect. XXXI. Of the Function of the Spleen . 45
Sect. XXXII. Of the Function of the Omentum 50
Sect. XXXIII. Of the Function of the Intestines 55
Sect. XXXIV. Of the Functions of the Absorbent
System. . 65
Sect. XXXV. Of Sanguification . 78
Sect. XXXVI. Of Nutrition . 83
Sect. XXXVII. Of Secretion . 90
Sect. XXXVIII. Of the Urine . 102
Sect. XXXIX. Of the Discrimination of the Sexes
in general . 110
Sect. XL. Of the Genital Function of the Male Sex. 114
Sect. XLI. Of the Genital Function of the Female
Sex in general . 133
Sect. XLII. Of Menstruation . 141
Sect. XLIII. Of the Milk . 146
Sect. XLIV. Of Conception and Pregnancy . 154
2 Sect. 

xvi CONTENTS.
Sect. XLV. Of the Nisus Formativus, or Formative
Effort. 174
Sect. XLVI. Of Parturition, and its Consequences 184
Sect. XLVII. Of the Differences by which the
Human Subject is characterised before and after
Birth . 191
Sect. XLVIII. Of the Increase, Maturity, and
Decline of Man . 200
APPENDIX . 213
3 ELEMENTS. 

ELEMENTS
OF
PHYSIOLOGY.
SECTION I.
OF THE LIVING HUMAN BODY IN GENERAL.
§ 1.
IN the living human body, the healthy
functions of which constitute the exclusive object
of the science of Physiology, there occur three
things worthy of our immediate attention and
regard*; namely,
The Solids, or parts containing;
* In an ancient volume commonly ranked among the wri-
tings of Hippocrates, Epidemic. VI. Sect. 8. § 19, we find the
following remarkable clause: " Quæ continent corpora, aut
" intus continentur, aut in nobis cum impetu moventur
" contemplanda sunt." This celebrated clause furnished
Abr. Kaau Boerhaave with the first hints and suggestions
Vol. I. A on

2 OF THE LIVING HUMAN BODY.
The Fluids, or parts contained within the solids ;
And lastly, the Vital Energies, which in the
consideration of the science of physiology, consti-
tute the most interesting and important object of
our regard. It is in consequence of these energies
that the solids are rendered alive to the impulse of
the fluids, endued with a power to propel the same,
and also to perform a variety of other motions.
It must however be observed, that these energies
are not incommunicably excluded even from some
of the fluids themselves: on the whole, they ap-
pear to constitute the essence or supreme charac-
teristic of an organised body.
§ 2.
But although these three objects have been with
propriety considered as distinct from each other,
and may therefore be separately enumerated on
the present occasion, they are notwithstanding in
the living body, which is alone the exclusive sub-
ject of physiology, so intimately connected toge-
ther, that it is scarcely possible to form even a
conception of one without at the same time em-
bracing the others.
on the subject of his inestimable work entitled, " Impetum
" faciens dictum Hippocrati per corpus consentiens." L. B.
1745-8.
The  

OF THE FLUIDS. 3
The most pure and limpid fluids of our body
abound with animal earth: on the other hand,
though our solids may appear to us completely
destitute of liquid matter, yet, besides the circum-
stance of their originating from the fluids as their
matrix or primary source, they contain in their
compostion an evident quantity of moisture:
lastly, if we be not deceived, it is certainly true
that there exists scarcely a fibril in the living
body which does not possess, in a higher or lower
degree, a vital energy inherent in itself.
§ 3.
We now proceed to treat of each of those three
objects separately and in order : and first of the
fluids; as constituting by far the greatest, and
what may be emphatically called the first-born
part of our bodies.
SECT. II.
OF THE FLUIDS OF THE HUMAN BODY IN GENERAL,
AND OF THE BLOOD IN PARTICULAR.
§ 4.
ALL the different fluids of our body,
may with propriety be thrown into three leading
classes.
A 2 These  

4 OF THE BLOOD.
These are, I. The Crude or unassimilised fluid,
consisting chiefly of the chyle contained in the
primæ viæ, and destined for conversion into blood;
to which may also be added, that fluid received
by absorption from the external superficies of the
body, and conveyed to the same receptacle with
the former.
II. The blood itself;
And Lastly, the secreted fluid, or that formed
from the volume of blood by the animal process,
called secretion : the fluids prepared by this pro-
cess are destined, some of them, to be retained in
our body, to serve further purposes in the animal
economy; and others, to be eliminated from our
system, as wholly excrementitious.
§ 5.
Of the first and third of those classes we will
speak on a future occasion, when we come to treat
of chylification, and of secretion, together with the
other functions to which those fluids are respec-
tively related. Let us now proceed to the consi-
deration of the blood, that most important, that
primary, and truly vital liquid, which may with the
greatest propriety be called, the living fountain
of all the other fluids; as being that into which
the crude fluid is converted ; and from which all
the

OF THE BLOOD. 5
the secreted fluids derive their origin ; and which
(a few parts of the body excepted, such as the
epidermis, the tunica arachnoidea, the amnion,
the vitreous substance, or enamel, of the teeth,
&c.) flows uniformly through every even the
most minute and fine spun parts of the inexplicable
texture of our system.
§ 6.
The blood is a liquid sui generis, of a well
known colour, more or less intense : it is glutin-
ous and warm to the touch : the formation of this
liquid has hitherto been ranked among the arcana
of nature, as it has never been successfully imi-
tated by any process of art.
§ 7.
This vital liquid when recently drawn from a
living subject, and received into a vessel, exhibits
in a very obvious manner the following remark-
able phenomena:
In the first place, while it is yet warm, a subtle
halitus ascends from it, which being collected in a
receiver, forms small pellucid globules, similar in
appearance to drops of dew ; it is of an aqueous
nature, resembling not a little common fountain
water, except that it emits a peculiar nidorous
smell, (still more considerable in the blood of car-
A 3 nivorous 

6 OF THE BLOOD.
nivorous animals) and which may be aptly called
the animal odour; such, for example, as arises
from fresh urine, or from the thoracic and abdo-
minal cavities of a dead subject recently opened.
Of this aqueous liquor a considerable quantity re-
mains in a state of mixture with the other consti-
tuent parts of the blood, which shall be hereafter
mentioned.
§ 8.
In the mean while, as the blood contained in
the vessel suffers a gradual reduction of tempera-
ture, it begins to separate into two parts. A
coagulum is first formed, from the superficies and
sides of which, there presently exsudes a liquor
of an intermediate shade between pale yellow,
and evanescent red, which they call the serum of
the blood ; in proportion as this liquor accumu-
lates by exsudation, a corresponding diminution is
observable in the volume of the coagulum itself;
the coagulum thus reduced in size has been dis-
tinguished by the name of crassamentum, as also
by those of the liver, and placenta of the blood,
from a resemblance, in point of colour and fran-
gibility of texture, supposed to exist between it
and these two bodies ; it has been likewise called
the island, from the circumstance of its being held
in a natant or floating state in the surrounding
serum.
§ 9. 

OF THE BLOOD. 7
§ 9.
This crassamentum itself, by a delicate treatment,
such as gentle agitation or frequent ablutions in
water, may be again separated into two constituent
parts, viz. the cruor, which imparts the red co-
lour to the whole mass of blood, and which by
ablution is carried off from the lymph, the other
and more substantial part, and which, therefore,
is called the basis of the crassamentum ; that the
cruor retains for this basis a much stronger af-
finity than the serum possesses, is sufficiently ob-
vious from this circumstance, that the cruor and
basis cannot be disparted unless by the interpo-
sition of a certain degree of force. The lymph
itself being robbed of the cruor, becomes more and
more pale until it finally assumes the appearance of
a white and considerably tenaceous coagulum.
§ 10.
Such then appears to be the four principal con-
stituent parts of the blood,—viz. the watery
halitus; the serum; the cruor, or red globules ;
and the coagulable lymph; which several parts,
as long as they retain their native degree of vital
temperature, continue in a state of the most
equable mixture, constituting an uniform and
homogeneous fluid.
A 4 It 

8 OF THE BLOOD.
It will now be proper to enter into a more mi-
nute consideration of those three portions of the
blood which stand last in the above enumeration :
As to the aqueous exhalation which we have men-
tioned, it does not appear of sufficient importance
to claim any further attention ; indeed as it is also
discovered in other parts of the body, it cannot
be considered as proper to the blood alone, any
more than the air which this vital fluid contains,
and on which we will state a few observations in
a subsequent part of this section.
§ 11.
The serum is a liquid of such a gelatinous nature
as to impart to the whole mass of the blood the
chief part of its viscosity or gluey consistence : it
very much resembles, in all its properties, the al-
bumen or white of eggs ; when subjected to the
action of a temperature equal to the 150th degree
on the scale of Fahrenheit's thermometer, it pas-
ses into a coagulum, white and easily broken
down, analogous to the white of eggs in a boiled
state; it also suffers a similar change, according
to the experiments of the celebrated Moscati, if
it be mixed with a quantity of quick lime, though
in this case the coagulation proceeds much more
slowly, and is not completed till after the twen-
tieth hour. But if the serum be dried with a
gentle heat, and left wholly undisturbed, it is
converted 

OF THE BLOOD. 9
converted into a firm pellucid mass, similar in its
external appearance to gum arabic, which in a
gradual manner, like the dried white of eggs,
cracks and forms over its surface numerous sulci
or fissures running in a somewhat spiral direction,
and exhibiting a very singular appearance.
§ 12.
Besides those other properties of the serum
already mentioned, there is one highly worthy
our consideration, to which my attention was first
called by the experiments of the illustrious
Priestley * ; but my belief of which has since
been fully confirmed by repeated observations of
my own, viz. the facility with which the air, sur-
rounding a vessel filled with blood, is able to act
through the medium of the serrum or the crassa-
mentum, though deeply covered by the former, in
such a manner as to produce a very remarkable
change in the colour of the latter, whereas, on
the other hand, the same action of the air would
be very much impeded, if not entirely prevented,
if instead of the serum, the crassamentum were
covered with any foreign liquid, such as water,
or oil, &c. or even with any other fluid of the
human body itself, as the saliva or urine.
* Philos. Transact. vol. LXVI. P. I. pag. 244, seq.
§ 13.

10 OF THE BLOOD.
§ 13.
The cruor constitutes another very striking and
important part of the blood, and is a source of
many singularities, whether we consider the
colour and figure of its particles, or the elemen-
tary parts into which it is resolved when subjected
to the action of an intense heat. It appears to
deserve a place among the most elaborate juices
of the body, as it seldom appears in the tender
fœtus previously to the fourth week after concep-
tion, nor in the nascent young of gallinaceous
fowls till the fortieth hour of incubation. After
profuse hemorrhages it likewise appears to be re-
placed by the powers of the system, with much
more difficulty than the other condiment portions
of the blood.
§ 14.
It consists of globules, first observed by Leeu-
wenhoek. In blood recently drawn they are al-
ways present, of a constant, uniform figure, and
of an equable magnitude ; which circumstances,
added to the further consideration, that in no
other fluid (milk alone excepted, the particles of
which are somewhat analogous), are similar
bodies to be met with, leave not a shadow of
doubt, but that those globules form a part very
obviously and essentially different from the other
constituent portions of the blood, though at the
same  

OF THE BLOOD. 11
same time the formation of those globular bodies
themselves appears in reality to be much more
simple than some celebrated characters would in-
duce us to believe. For to pass over in silence
the complexity of the sixfold form fictitiously be-
llowed on them by Leeuwenhoek, neither the an-
nular figure attributed to them by the illustrious
de la Torre, nor the form of vesicles enclosing an
opaque nucleous, such as Hewson apprehended he
discovered in them, have appeared to me to be
well founded*. In my observations, indeed, I
have been able to detect nothing more than bodies
of a simple spherical appearance, and, if I am not
deceived, of a solid gelatinous consistence. I have
not, indeed, absolutely denied the lenticular figure
bellowed on them by some observers : I dare not,
however, venture to assert, that I have been so
fortunate as to observe it.
It has been a subject of controversy whether or
not they can alter their figure when it becomes
necessary for them to pass through a vessel of a
very narrow diameter. I am inclined to believe,
in conformity to the opinion of that accurate
observer Reichel that under the above circum-
stances, they do actually change their spherical
for an oval figure, and again resume their former
* Philos. Trans. Vol. LXIII. P. II. p. 303. seq. tab. XII.
globular 

12 OF THE BLOOD.
globular Shape, when they advance into vessels
sufficiently capacious; though I must confess, I
never had the happiness to be a spectator of this
interesting phenomenon.
This spherical figure of the globules is never
perceived unless in the blood circulating in the
vessels of a living animal, or in that which is re-
cently drawn ; they lose all regularity of form in
process of time, and appear to dissolve, as it were,
and again unite with each other into one uniform
shapeless mass.
§ 15.
Physiologists differ in determining the size of
the globules of the blood. Hales reckons them
equal in diameter to the 1/324th part of an inch.
Senac estimates their diameter at about the 1/3000th
part of the same measure, while others again en-
tertain different opinions.
§ 16.
Their colour is red, and therefore the beautiful
crimson call of the whole mass of blood appears
to be evidently derived from them. The intensity
of this colour changes with a multiplicity of vary-
ing circumstances ; it is more pale in animals which
are too sparingly nourished, or in such as have
suffered profuse hemorrhages. The blood con-
contained 

OF THE BLOOD. 13
tained in the arteries is more florid, together with
that which has been subjected to the action of
atmospheric, but more especially, that which has
been exposed to dephlogisticated air ; while venous
blood is more obscure, as well as that which has
been acted on by fixed or inflammable air.
§ 17
Upon the whole, the causes, which augment
the quantity of the red globules in general, and
also heighten the intensity of their colour, are
sufficiently evident: but to discover from what
Secret Source their disposition to this crimson dye
is originally derived, is a matter of Herculean
difficulty indeed. Haller ascribed it to the pre-
sence of crocus martis, because the blood abounds
more with iron than the bones, or other parts of
the body, although the quantity contained, even
in the blood itself, is very small; and although
authors differ astonishingly in their attempts to
ascertain it. Thus, for instance, Menghinus esti-
mated its relative proportion to the whole mass of
the blood, to be as 1 to 110; whereas, the illus-
trious Rhades calculated it to be only as 1 to 427 ;
and again, in some suture experiments, to be no
more than as 1 to 503, &c.
On the present subject it seems proper to make
the following observation; viz. that no iron can
be 

14 OF THE BLOOD.
be discovered in the cruor of the blood unless it
be previously calcined; whereas, on the other
hand, when it was dried with a gentle heat, and
reduced to the most impalpable powder, I could
not observe a single particle of it attracted by the
magnet, whether the experiment was made in
water, or in that most fluid of all vehicles, quick-
silver.
§ 18.
We now come to the consideration of that con-
stituent part of the mass of blood, which stands
last in our order of enumeration, viz. the Lymph;
which is by some called the basis of the crassamen-
tum, by others, the mucous or glutinous part,
and by others, the fibrous portion of the blood.
This, in former times, was very erroneously
confounded with the serum, from which it is not-
withstanding very widely different, in all its essen-
tial properties. When the lymph is exposed to the
action of air, especially of such as is of a low tem-
perature, it is immediately coagulated ; but by the
admixture of quicklime, (which has been already
said (§ 11.) to have the power of coagulating
serum), it is preserved in a fluid state; or, even
though it be already coagulated, yet, by the
addition of this substance, it is again immediately
resolved.
§ 19. 

OF THE BLOOD. 15
§ 19.
We have already touched on the methods, by
which this part of the blood may be separated
from the cruor (§ 9.). It is also by other artifi-
cial methods, Such as whipping or agitating the
blood with small twigs, induced to assume the
appearance of a membrane, which has been named
after Ruysch its celebrated discoverer.
The similitude which prevails between the mem-
brane thus formed by art, and certain remarkable
phenomena in diseases, especially in those of an
inflammatory nature, reduces it to a certainty,
that such phenomena are to be entirely referred
to the coagulation of the lymph, of which we are
now treating.
It may be proper on the present occasion to
mention a few of those numerous phenomena al-
luded to, which evidently derive their origin from
this property of the lymph ; thus we may instance
in particular, the pleuritic crust, which is formed
on the surface of the crassamentum of blood re-
ceived into a vessel and suffered to remain some-
time at rest ; the membrane-like appearances which
usually transude from, and completely invest the
surfaces of the several viscera when in a state
of inflammation ; and also the membrana caduca
of

16 OF THE BLOOD.
of Hunter, which exsudes from the cavity of the
uterus, when impregnated, and still under the
gentle glow of the venereal orgasm. From the
same source originates likewise, that production of
cellular membrane by which we see frequently the
lungs connected to the pleura in cases of peripneu-
mony; as also the preternatural portions of the same
substance often found in the cavity of the abdomen
after profuse hemorrhages ; and finally, to no other
source can we rationally refer those membrane-
like productions, which, in that singular species
of disease, vulgarly denominated Lithopœdion,
firmly attach to the contiguous viscera such parts
as are irritated to inflamation by the too long re-
tention of the calculus or stone in the abdominal
cavity. It seems to be also an opinion founded at
least on probability, that polypi, and such like 
preternatural coagulated excrescences, owe their
existence to the same cause.
§ 20.
Those phenomena just enumerated, together
with a variety of others which every where occur,
demonstrate, in a most striking manner, the Superior
importance of this lymphatic portion, in which
the vital principle of the blood appears immedi-
ately to reside, if indeed the blood possess any such
principle, an opinion which I think both ingeni-
ous and highly probable.
2 Besides 

OF THE BLOOD. 17
§ 21.
Besides those general portions of the blood al-
ready enumerated, we have on a former occasion
observed that this fluid contains also, in a state of
mixture, other elementary principles. (§ 10.)
What I principally advert to at present is air,
Which is commonly believed to constitute 1/33 part
of the whole mass of blood, but which in the
blood of a living and healthy subject does not
exist in a free and perfectly elastic state, but is so
intimately united and involved, and so permanent-
ly fixed, as to be with difficulty extricated and
restored to its native æriform state. Indeed I
have learned from actual experiments, that even a
very small quantity of the most pure air injected
through an artificial opening into the jugular vein
of a dog, has excited symptoms of a very formida-
ble nature, such as palpitations of the heart, drowsi-
ness, convulsions, and, when the quantity was slight-
ly increased, even death itself quickly succeeded.
§ 22.
The elementary parts of the blood thus concise-
ly treated of, differ very widely in the proportion
they bear to each other in different subjects, ac-
cording to the complex ratio of age, nourishment,
and other circumstances of importance, which re-
gard the sound health of each individual.
VOL. I. B § 23. 

18 OF THE SOLIDS.
§ 23.
Neither has any thing more certain or decisive
been advanced with respect to the proportion which
the whole volume of blood bears to the entire
bulk of the body. Haller was of opinion, that in
an adult it amounts to 30 or 36 pounds by
weight; while the calculations of others have been
widely different.
SECT. III.
OF THE SOLIDS OF THE HUMAN BODY IN GENERAL,
BUT PARTICULARLY OF THE CELLULAR MEM-
BRANE.
§ 24.
THE solids of the body are originally
derived from the fluids themselves; thus in the
first rudiments of the embryo, while yet in a gela-
tinous state, the solids, each in its own appropriate
situation, begin in a very gradual manner to as-
sume their proper form and texture, infinitely dif-
ferent from each other in point of cohesion, from
the most tender and almost pultaceous consistence,
such as the medullary substance of the brain, to
the most firm and durable, as the vitreous cortex,
or enamel of the teeth.
§ 25.

OF THE SOLIDS. 19
§ 25.
In all the solids of the body an earthy basis of
a calcareous nature abounds more or less, not in-
deed in a simple state, but united to the phos-
phoric and saccharine acids, the former of which
exists in by far the largest proportion. Their co-
hesion depends not only on the peculiarity of their
texture, but is also much promoted, as well by
the quantity of air contained in them in a fixed
state *, (which is ascertained by the experiments
of the illustrious Hales to be more abundant as the
parts are more solid); as also by the substance
called animal glue, which is procured in large
quantities from the solid parts of animal bodies,
and is in general use in some of the mechanical arts.
The origin of this tenacious substance may be
very easily explained and comprehended from
what has been already said respecting the viscosity
or gluey nature of the blood.
* " The properties and powers of air have not yet been
ultimately developed. It is, however, in the mean time
certain, that this substance constitutes, at least, a part of the
gluten or cement by which all the more compact bodies
in nature are consolidated and bound together. Thus the
dissolution of metals, bones, stones, shells, and salts, is uni-
formly attended with an extrication of air." See Haller de
corp. hum. functionib. Vol. III. pag. 271.
B 2 The 

20 OF THE SOLIDS.
The elementary substance of iron, to which has
been attributed the important office of increasing
the powers of cohesion in the different parts of
the human body, scarcely deserves to be taken
into consideration at all, as I have found its quan-
tity to be so very minute as not to exist in a
greater proportion than one fifth part of a grain
to two pounds even of the bones, the hardest and
most coherent parts of the animal system.
§ 26.
A great portion of the solids of our body very
evidently exhibits a fibrous texture, composed of
small filaments running more or less parallel to
each other. These filaments or fibres may be
evidently enough perceived in the bones, espe-
cially the bones of a fœtus, in the muscular flesh,
in tendons, ligaments, aponeuroses, and some mem-
branes, as the dura mater, &c.
§ 27.
In various other parts of the animal body, the
texture is so widely different from that of which
we have just spoken, that in them it is scarcely
possible to trace the appearance of a single fibre ;
their structure is indeed of a very singular and spe-
cific nature, distinguished in Greek by the name
parenchyma. This parenchymatous substance is
almost exclusively confined to some of the secreting
viscera 

OF THE SOLIDS. 21
viscera of the system ; thus it exists in the kidneys,
in the liver, &c. though assuming a somewhat dif-
ferent and peculiar appearance in each.
§ 28.
Through all those varieties of composition and
texture, whether of a fibrous or parenchymatous
appearance, there is interwoven, in common, more
or less of a certain web-like substance, which is
called cellular membrane, and which deserves a
place among the primary, the most important and
essential, constituent parts of our system.
§ 29.
For, in the first place, there are several of the
solid parts of the human body, which appear to
consist of little else than cellular membrane, in a
constipated or compacted state; of this description
are most of the membranes and cartilages ; which,
by long maceration, may be again resolved into a
cellular web, of more or less laxity. It is, again,
so intimately and minutely interwoven in the com-
position of other parts, as to serve the important
purposes of a receptacle and basis to the other
portions of substance which assist in their formation.
Thus, for instance, the hardest bones made their
first appearance in the tenderer state of cartilage,
which, as already observed, is nothing more than
condensed cellular membrane: this cellular mem-
brane, yet in a lax condition, became afterwards
B 3 distended, 

22 OF THE SOLIDS.
distended, and at length completely Saturated, as
it were, by the constant accession of osseous matter,
till it finally assumed the nature and appearance of
perfect bone. Indeed it would appear, that none
of the solids of our body exist, without containing
more or less of this web-like substance in their
composition, if we except the enamel of the teeth,
in which I was not able to discover the smallest por-
tion of cellular substance, even when the enamel
was subjected to the action of one of the stronger
acids.
§ 30.
This cellular substance, which serves the great
purpose of a boundary, or partition-wall, to adja-
cent parts, is especially interwoven in, as well as
spread between, muscles and membranes. To other
parts, again, particularly to vessels and nerves,
it answers as a bed or basis of support. Finally,
it constitutes one common and general bond of
union, which connects the neighbouring individual
parts to each other, and establishes between the
whole an extensive medium of communication,
§ 31.
From what has been already said, two conclu-
sions naturally present themselves.
First, in as much as it appears, that the cel-
lular membrane certainly constitutes the ground-
work 

OF THE SOLIDS. 23
work of the structure of the whole body, if we
figure to ourselves the entire removal of every
other substance which enters into, and assists in
completing, the composition of the system, the
cellular membrane, still remaining in its proper
situation, unmolested and alone, will nevertheless
preserve and exhibit the complete figure of the
whole and every part of the body.
Secondly, as by means of this cellular founda-
tion, a certain connection and medium of commu-
nication are formed, between all the parts of the
body, however widely different from each other
they may be, in nature, or remote, in situation 
the knowledge of this fact serves an important end,
not only in deciding controversies which respect
the continuation of membranes, but also in explain-
ing many phenomena of diseases which daily pre-
sent themselves.
§ 32.
As the cellular membrane appears thus to afford
origin and foundation to most of the solid parts of
the body, so it appears itself to owe its own exis-
tence to the lymphatic part of the blood, of which
we have already spoken. I am induced to enter-
tain this opinion from having seen the lymph, after
transuding from the lungs of pleuritic patients,
converted by the powers of the animal economy
B 4 into 

24 OF THE SOLIDS.
into real cellular substance, which afterwards
assuming the appearance of more compacted mem-
branes, oftentimes attaches those viscera to the
surrounding pleura.
§ 33.
What has been already advanced on the subject,
may be sufficient to show the general nature, and
establish the importance, of the cellular membrane.
We will now proceed to consider some of its
varieties.
And, in the first place, its firmness is not always
uniform.
For, in general, other circumstances being alike,
the cellular membrane of the human body is very
tender indeed, when compared with that of other
animals. If I am not deceived, this very softness
and pliancy of the cellular substance in the human
system, deserves to be ranked among the leading
prerogatives of man ; because, in consequence of
it, his susceptibility of impressions from the more
refined and subtle stimuli is greatly increased, as
well as his capacity to perform motions and vari-
ous functions, with facility and perfection.
But with regard to the more lax or firm texture
of the cellular membrane, even among mankind
themselves, 

OF THE SOLIDS. 25
themselves, a very great variety occurs, depend-
ing on age, sex, mode of life, climate, &c.
Finally, the condition of this membrane as to
density and firmness, is various, as it is found
existing in different parts of the same body : thus,
it is more lax on the eye-lids and prepuce, more
compact and firm about the ears, &c.
§ 34.
We now proceed to consider another use or
office of the cellular membrane, besides that
which we have already said it performs to the
body in general, (§ 29, 30) ; namely, that by
means of its numerous small cells, it affords con-
venient temporary receptacles for fluids of different
kinds.
That fluid, which those minute cells are more
particularly destined to receive, is a fine halitus of
a serous nature, or a very subtle water, by which
almost all parts of the body are moistened, and
lubricated, and which this cellular web appears to
absorb, after the manner of a sponge*.
If it be admissible to designate by the name of vessels,
those minute interstices of the cellular membrane, by which
it absorbs fluids after the manner of a sponge, I readily
acquiesce in the opinion of William Hunter, (see Medic. 
Obs.

26 OF THE SOLIDS.
§ 35.
But, besides this, the cellular membrane, in
certain parts of the body, serves as a reservoir to
humours of a different and somewhat specific na-
ture. Thus, that portion of it which constitutes
the vitreous substance of the eye, is charged with
a fluid of the same name;
That which forms the meddullary membrane
of the bones (commonly, though improperly, cal-
led the internal periosteum) contains the medulla:
and,
Finally, A large portion interwoven through
the soft parts of the body, furnishes a convenient
receptacle for the other portions of oily substance.
Obs. and Inquiries, vol, ii. p. 27. seq.) that this web-like
expansion, now under immediate consideration, is composed
of a congeries of vessels, in like manner with the other parts
of the body. But if he entertained a belief, that this mem-
brane consists of small cylindrical veins, which anatomists
commonly mean to represent by the term vessels, I must
acknowledge, that microscopical observations, conducted
with the utmost degree of minuteness, and the most cautious
circumspection, have not been sufficient to furnish me with
any unequivocal testimony that such vessels actually exist,
but have rather induced me to embrace a contrary opinion.
§ 36, 

OF THE SOLIDS. 27
§ 36.
And here indeed a threefold variety presents
itself to our consideration :
There are, in the first place, certain parts of
the body, the cellular substance of which, though
of a very soft and extremely flaccid nature, is
notwithstanding, never filled with fat in a healthy
subject; such, for instance is that which lines the
eyelids, and that spread on the genital organs of
the male, &c. But further, in numerous parts
throughout the body, there are not unfrequently
found irregular and transient collections of fat,
which appear to reside in the same kind of cells,
which at other times act as reservoirs to the atte-
nuated serous fluid already mentioned.
But finally, in certain parts of the body, and,
unless I am deceived, in cells of a peculiar nature,
and given description, fat is found constantly en-
closed, designed to subserve stated, uniform, and
specific uses in the animal economy, such, for ex-
ample, is that which, in the female system, forms
the mons veneris, which appears to me to consti-
tute a very peculiar and completely circumscribed
protuberance *.
* This circumstance I had an opportunity of ascertaining
in a much more satisfactory manner in the dead body of a
female ape. After having for some time subjected the corpse
to the action of cold, I was able, by removing the skin, to
expose 

28 OE THE SOLIDS.
§ 37.
On the subject of the fat itself we will now pro-
ceed to make a few observations, this being so
very proper a place for entering on the considera-
tion of it.
It is an oil, not unlike the unctuous oils of ve-
getables ; bland, inodorous, and lighter than
water, consisting of phlogiston, united to phlegm
by means of an acid of a peculiar nature.
§ 38.
It is formed at so late a period in the fœtus,
that scarcely an indubitable vestage of it can be
discovered earlier than the fifth month after con-
ception.
Its consistence is various in different parts of
the body. That for instance which lines the in-
side of the orbit of the eye, is more fluid, whilst
that on the contrary which surrounds the kidneys
approaches to the firmness and appearance of suet,
§ 39.
A controversy has existed with respect to the
secretion pf this substance, namely, whether it is
performed by a peculiar set of glandular bodies,
expose entire the circumscribed globe of fat situated beneath
the pubes.
agreeably 

OF THE SOLIDS. 29
agreeably to the opinion of William Hunter, or
whether it merely transudes, by simple diapedesis,
through the patulous mouths of arteries ? The
latter of these opinions, besides other arguments
which might be advanced in its favour, appears
the most probable from hence, that not unfre-
quently preternatural collections of fat have been
discovered in other parts than those commonly oc-
cupied by this substance: this circumstance can be
much more aptly and rationally explained by at-
tributing such unusual collections of fat to an error-
loci, arising from a morbid state or disposition of
the vessels, than by referring it to an unnatural
and recently formed system of glands: thus for
example, in the very ball of the eye itself, fat has
been sometimes found ; and a substance of a na-
ture like suet, usually fills up the cavity from
which a testicle has been extracted; indeed there
scarcely exists a cavity in the body in which stea-
tomatous collections have not made their appear-
ance.
But to conclude; those small glands to which
certain celebrated characters have been solicitous
to attribute the secretion of fat, appear as yet to
be in reality nothing more than mere creatures of
analogy.
But 

30 OF THE SOLIDS.
But however this may be determined, it is in
the mean time very certain, that both the secre-
tion and absorption of this substance can be per-
formed with the utmost dispatch.
§ 40.
The uses of the fat are numerous. It lubri-
cates the solids, and thus facilitates motion. It
obviates and prevents a morbid excess of sensibi-
lity. It acts as a defence against cold: and,
finally, by its uniform distention of the skin, con-
tributes to comeliness and beauty. Not to men-
tion the peculiar uses of the fatty matter con-
stantly bestowed on certain parts of the body, as
the medulla of the bones, &c.
This substance appears, however, to contribute
scarcely any thing to the nourishment of the hu-
man species*, when in the enjoyment of entire
health.
* That bloodless insects, however, derive a principal part
of their nourishment from the fatty substance with which
their bodies are plentifully supplied, is a conjecture of natu-
ralists founded at least on probability.
SECT. 

OF THE VITAL ENERGIES. 31
SECT. IV.
OF THE VITAL ENERGIES IN GENERAL, BUT
PARTICULARLY OF CONTRACTILITY.
§ 41.
We enter now on the consideration of
a difficult subject, namely, the living solid, and
shall attempt a full account of the vital energies,
by which the different parts of our body appear
to be animated and fitted, as well to receive the
impulse of stimuli, as to perform the various mo-
tions which are necessary in the economy of the
living system.
§ 42.
But with respect to the living solid, it will first
be necessary to ascertain its exact limits, and to
define it with precision and accuracy; whence it
will evidently appear, that it is not our intention,
on the present occasion, to treat either of those
properties, which the human body possesses in
common with numerous other bodies in nature,
such as elasticity (the powers of which, however,
are notwithstanding exhibited in various motions
and functions of the animal economy), nor yet of
those which reside exclusively in the mind; tho'
we flatter ourselves no one will deny the powerful
influence of these latter over the energies possess-
ed 

32 OF THE VITAL ENERGIES.
ed by the living solid itself, considered as a mate-
rial body. We will confine ourselves solely to
the consideration of those energies which reside in
our body as a system of organised matter, and
which appear to be related to each other in the
following order.
§ 43.
The first and most universal species of those vi-
tal energies, and which may indeed be regarded as
an inferior degree of the others, or rather as the
threshold leading to them, is simple contractility,
i. e. a propensity in a part to contract itself. As this
property appears in reality to reside in every part of
the cellular membrane, it must be equally exten-
sive with that membrane itself, and therefore may
be said to pervade almost the whole body. Hence
this may be called, with perhaps sufficient propri-
ety, the vis cellulosa.
§ 44.
Another of the vital energies is, the irritability
of Haller, which resides in muscular fibres only,
and may therefore be called the vis muscularis.
It manifests itself by a very singular, oscillatory
and tremulous motion, easily distinguished from
simple contraction, by its being more readily ex-
cited to action on the application of any acrid sti-
mulus.
4 § 45. 

OF THE VITAL ENERGIES. 33
§ 45.
The third is sensibility, which resides solely in
the nervous medulla, communicating with the sen-
sorium, called therefore vis nervea; when any
part endowed with this property is acted on by
irritating stimuli, an impression is immediately
made on the sensorium. 
§ 46.
The three foregoing may be, with propriety,
considered as common or general vital energies ;
because they exist, more or less, in almost all, or
at least in a great many, parts of the body, which
the ancients called therefore similares, i. e. parts
of a similar nature.
§ 47.
But besides the foregoing, there exists also a
fourth energy worthy of our consideration, namely,
the vita propria, or specific life; under which deno-
mination I mean to arrange such powers as belong
to certain particular parts of the body, destined for
the performance of peculiar functions, and which
cannot with any propriety be referred to either of
the classes of common energies, formerly mentioned.
Inferring synthetically, or a priori, as it is
termed, it is not repugnant to sound induction to
conclude, that parts differing from all others in
VOL. I. C texture, 

34 OF THE VITAL ENERGIES.
texture, in arrangement, and in peculiarity of
function, must also be furnished by nature with
peculiar properties and powers, adapted to the
performance of such specific action.
But reasoning analytically, or a posteriori, we
are likewise taught by accurate observations made
on nature herself, that there are certain parts of
the body, particularly some of the viscera, which
perform motions so very singular, as cannot by
any means be supposed to arise from either one or
other of the common energies, of which we have
already spoken, but must be referred to a vita
propria, or specific energies of their own.
Instances of such sigularity of action we have in
the motions of the iris ; the erection of the papilla
in the breasts of females ; the motions of the fim-
briæ of the fallopian tubes ; the action of the
placenta ; the action of the uterus in parturition ;
the descent of the testes in the male fœtus ; and,
if I am not deceived, in a great part, if not in the
whole of the process of secretion.
§ 48.
The fifth and last energy which claims our at-
tention is, the nisus formativus, or formative pro-
pensity, which should be considered as the efficient
cause of the whole process of generation (taken in
so 

OF THE VITAL ENERGIES. 35
so extensive a latitude as to include both nutrition
and re-production as modifications of itself). In
consequence of this propensity, the matter of the
animal system, whether appropriated to generation
or nutrition, being lodged in the places destined
for its reception, and having acquired sufficient as-
similation and maturity, assumes forthwith its due
arrangement and figure, and enters into the com-
position of those parts which are afterwards fur-
nished and enlivened either with the whole or
part of the energies we have already enumerated,
viz. contractility, irritability, sensibility, or finally
specific life.
§ 49.
Of this nisus formativus, or formative propen-
sity, more will be said when we come to treat of
the process of generation.
Irritability will be more fully considered when
on the subject of muscular motion.
The subject of sensibility will be again resumed
when we come to consider the action of the ner-
vous system.
Of the vita propria, or specific life, we will
every where treat, when the subject under consi-
deration may render it proper.
C2 But

36 OF THE VITAL ENERGIES.
But with respect to contractility, the present
is a very suitable place to offer on it a few addi-
tional and particular observations.
§ 50.
I have already said that this energy pervades
almost the whole body, at least, that its extent is
commensurate with the extent of the cellular
membrane.
In the first place, therefore, it resides in all
such parts as consist of compacted cellular sub-
stance, of which the different membranes of the
body serve as examples. That these possess con-
tractility will not be denied by any one who re-
flects on the constriction of the dartos tunic, or
who calls to mind the spasms of the skin, or of
the peritoneum, which alone appears sometimes
to incarcerate and strangle the intestines in cases
of hernia.
Further, It also exists in such viscera as are
composed chiefly of this kind of membrane ; of
this description are the lungs, the external super-
ficies of which is highly contractile, as I have
lately learned from frequently puncturing and irri-
tating them in a living state ; but I have not found
them possessed of any real irritability, as has been
lately asserted by Varnier.
Even 

OF THE VITAL ENERGIES. 37
Even the bones themselves do not appear to be
entirely destitute of contractility, as we learn, not
only from the alveoli, which are well known to
become narrower after the extraction or loss of
the teeth, but also from the morbid affection term-
ed necrosis (i. e. mortification), from which it ap-
pears, that after a lifeless part of bone is quite re-
moved, the new production of bone, by which
the vitiated part was before surrounded, contracts
itself very gradually, almost to the natural thick-
ness and former figure of the part.
But as we observed on a former occasion,
that the vitreous substance of the teeth was quite
destitute of cellular membrane, so it appears to
me probable, that it is entirely destitute of con-
tractility also, because when a part of it is either
consumed by a caries, or broken off by accident,
the remaining portions or sides are not approxi-
mated to each other, as we have already said takes
place in the alveoli, but an irreparable hiatus or
chasm continues without a shadow of diminution.
§ 51.
This very power of contraction, possessed by the
cellular membrane, should be ranked among the
primary and leading securities or supports of firm-
ness and health ; and to it should be referred that
tone of parts, so highly and favourably spoken of
C3 by 

38 OF THE VITAL ENERGIES.
by the acute and ingenious Stahl. To advance
one argument in favour of the foregoing position,
from many which might be adduced, it is the cel-
lular substance which, in a healthy subject, ab-
sorbs, after the manner of a sponge the aqueous
liquid, of which we have already spoken, and by
means of its contractility propels it forward into
the lymphatic vessels: on the contrary, in a dis-
eased state, being deprived of its proper tone, and
reduced to an atonic condition, it becomes op-
pressed and distended with a load of water, and
thus gives rise to œdema and other cachectic
symptoms.
§ 52.
Finally, from the universal prevalence of con-
tractility throughout the whole body, we may
plainly infer its influence and contagious effect, as
it were, on the other vital energies ; and also from
its infinitude of modifications and degrees in dif-
ferent men, we learn its highly influential part in
the constitution of both the proper health and pe-
culiar temperament of each individual.
SECT. 

OF SOUND HEALTH. 39
SECT. V.
OF SOUND HEALTH, AND OF THE NATURE OF MAX.
§ 53.
THOSE three subjects (§ 1.) in the
consideration of which we have been hitherto en-
gaged, perpetually act and re-act on each other in
the living human body. The fluids, for example,
act by their stimulus on the solids; while these
again, in consequence of their vital energy, are
fitted and prepared both to receive the action of
the stimulating fluids, and to re-act on them in
turn. In a sound and healthy subject, this whole
routine of action and re-action, corresponds with
such exactness and definitude, as to constitute a
perfect and harmonious equilibrium.
§ 54.
There further exists in the living system a won-
derful consent of parts, even the most remote;
this consent is derived not from one, but seems to
owe its origin to different sources.
One of those sources resides in the nerves, de-
pending as well on the astonishing net-like anasto-
moses, formed by their numerous branches, as on
the intricate nature of their plexus and ganglia ;
C 4 by 

40 OF SOUND HEALTH.
by the medium of which, the impulse of stimuli
being communicated to the sensorium, may from
thence re-act on parts more remote.
Another source of this wonderful consent must
be referred to the different vessels of the system,
as well the sanguiferous as the lymphatic.
Another, again, arises from a certain similitude
of structure, giving origin to what may be called
a native sympathy.
The cellular membrane, which, as has been al-
ready observed, appears to constitute a common
bond of union to the whole body, may be readily
conceived to possess a very striking and powerful
influence in promoting the consent of distant parts,
§ 55.
Finally, to this head belongs what is justly es-
teemed one of the greatest mysteries of nature,
namely, the connection of the mind with the
body, and the diversified and astonishing power of
the one over the other. As this subject will be
again resumed, and treated more fully in another
place, it will be sufficient on the present occasion
briefly to observe, that besides the obvious power
of the will over most of the muscles, there are
also other faculties which exert their influence on 
the

OF SOUND HEALTH. 41
the body, even without the concurrence or aid of
the will.
Of this description are those blind and purely
animal instincts of our nature ; such, for example,
as that which excites to the gratification of vene-
real enjoyments.
Further, the body is greatly under the influence
of the internal senses, more especially of the ima-
gination, and those passions of the mind which it
contributes to excite.
Finally, it is by the interposition, and through
the medium of these, that a communication and
reciprocal influence are preserved between the
powers of the body, and the more exalted facul-
ties of the mind.
§ 56.
By this diversified consent of the solids, of the
fluids, and of the vital energies (§ 53.), by this
sympathy of parts (§ 54.), and by this intimate
connection between the mind and the body,
(§ 55.), life and health are preserved in vigour ;
yet not always existing in the same, but in widely
different degrees of perfection and energy.
§ 57. 

42 OF SOUND HEALTH.
§ 57.
Between the two extremes of life there exist
different grades, of which one is called vita max-
ima, or perfect life; the other vita minima, or im-
perfect life.
Life is said to be perfect in the flower of age,
when the functions of the body have reached that
pinnacle of perfection, called by the Greeks acme;
this might also be denominated the athletic state.
Life, on the other hand, is said to be imperfect
when the functions are performed with less vi-
gour ; although their perfection may be the most
consummate, when the situation of the subject, and
its mode of existence, are taken into considera-
tion : thus life is imperfect in a fœtus in utero,
and that in proportion as the fœtus is tender and
young. Finally, life is less perfect in the sleeping
than in the waking state ; less perfect also in a
subject advanced in years, than in one basking in
the meridian blaze of manhood.
§ 58.
The varieties in point of health are no less nu-
merous and considerable : there is indeed a cer-
tain state of health which may be said to be pecu-
liar to each individual. Such persons as we sup-
pose 

OF SOUND HEALTH. 43
pose to be in the enjoyment of the most complete
health, differ, notwithstanding surprisingly from
each other, as well in consequence of a difference
in the constitution of the blood, as of a diversity
of tone, and of the other vital energies; hence
different individuals are so differently affected by
the same stimuli acting on their bodies. Perhaps
each individual may possess peculiar idiosyncra-
sies, though so very inconsiderable as to be scarce-
ly observable : the influence of custom is so pow-
erful, as to create, in different subjects, an intole-
rance of different impressions, though in them-
selves quite innocent; it also produces a facility of
bearing, and finally creates a desire for, such
things as appeared at first both unnatural and dis-
agreeable.
§ 59.
This appears to be the very hinge on which re-
volves the nature and variety of temperaments. so
frequently the subjects of physiological discusion.
The constitution of the temperaments depends, not
only on the proportion and mixture of the consti-
tuent parts of the blood (§ 22.), but also on the
peculiar vigour of the vital energies already treat-
ed of; and likewise en the consequent variety in
the mode of the reciprocal action and re-action of
the body and mind on each other. From this
combination and concurrence arises that peculia-
rity 

44 OF SOUND HEALTH. 
rity of sensation to the impressions of stimuli ; and
also that singular power of performing motions
with greater or less facility.
§ 60.
Hence the varieties of temperaments are lite-
rally infinite, and can never be reduced to any
certain and definite classes. But as it has been
the pleasure of physiologists to arrange them un-
der certain heads, for the sake of regularity, we
may with sufficient propriety give our assent to the
common mode of arrangement, by which they
have been reduced to four orders, namely, the
phlegmatic, the sanguineous, the choleric, and the
melancholic.
§ 61.
For although Galen erected this division on an
absurd foundation, falsely supposed to be derived
from the nature and constituent parts of the
blood, yet if this erroneous foundation be kept
entirely out of view, the division appears in other
respects so consonant to nature, that the different
temperaments of all men generally, and of every
individual in the different periods of life, may be
with propriety referred to one or other of these
four leading classes. Thus, in the tender age of
infancy the phlegmatic temperament chiefly pre-
vails. This in youth is exchanged for the san-
guineous. 

OF SOUND HEALTH. 45
guineous. The choleric marks the period of man-
hood. And the melancholic is the temperament
of old age.
But, as has been already observed, the variety
in the existing degrees of the same, and in the
mixtures of different temperaments, is so un-
bounded, as to afford an open and a very exten-
five field of speculation to such as would wish to
amuse themselves with tracing out, and establish-
ing, on this subject, more minute combinations, or
divisions and orders.
§ 62.
This whole collective assemblage of all the fa-
culties and laws hitherto mentioned, by which the
functions of the human body are performed and
regulated from the opening, to the closing pulse
of life, are called human nature, or the nature of
man; from whence arose the name of physiology,
the science now under our immediate consideration.
§ 63.
Those functions of the body may be themselves
properly enough divided into four classes ; which
division, although not entirely free from exception,
nor perfectly conformable to nature, may never-
theless be aptly enough retained as a useful assist-
ant to the memory.
I. The 

46 OF SOUND HEALTH.
I. The first class of this division embraces the
vital functions, So called because their incessant
and unmolested action, is more especially and es-
sentially necessary to the continuance of life. To
this class belong the circulation of the blood, and
after birth the process of respiration.
II. The second class embraces the animal func-
tions; these serve to distinguish animals from or-
ganised bodies belonging to the vegetable king-
dom *. This class in man includes the connection
* I lament it as a serious misfortune to the science of na-
tural history, that his final object did not call on the very
learned and ingenious professor to be more explicit and mi-
nute on that class of functions denominated the animal. He
has told us in terms very general and definite, that they are
such as serve to constitute the great barrier of distinction be-
tween animal and vegetable bodies. I am sorry that neither
the object nor extent of an elementary work permitted him to
descend to a more minute specification of those characteristics,
in which the difference between animals and vegetables more
immediately consists. Few points of investigation can be
proposed which have given rise to a greater diversity of opi-
nion, than that which respects the difference between these
two classes of natural bodies ; and fewer still perhaps can be
advanced, with regard to which philosophers, even in the pre-
sent imperfect state of physical science, should more unani-
mously agree. Be this later position, however, true or false,
I have always been led to consider the strangely diversified,
and even contradictory opinions, entertained by naturalists
respecting the difference between animals and vegetables, as
so  

OF SOUND HEALTH. 47
of the mind with the body, but it regards more
especially sensation, and muscular motion.
so many unanswerable testimonies of the equivocality of the
whole. The discovery therefore of an exclusive line of dis-
tinction between the animal and vegetable kingdoms, (if in-
deed the supreme author and arbiter of nature permits such a
line to exist) must still be considered as a peculiar desideratum
in the science of natural history.
From all my speculations on this interesting subject (and
it is with me a favourite object of pursuit) I am firmly of
opinion, that there exists no incommunicable characteristic,
and I will venture to add, no congregation of characteristics,
which serve to constitute a complete partition-veil between
the animal and vegetable kingdoms. The numerous and
highly diversified subjects of these two important kingdoms
of life, appear to be nothing else than different individuals of
one extensive family, descended from a common parent, and
exhibiting the most unequivocal testimonies of their kindred
nature. Like the delicate tints of light and shade in a well fin-
ished picture, they so gradually intermingle, and run into each
other so insensibly, that it is literally impossible to say with
definitude, where the one terminates and the other begins
All researches therefore after an exclusively distinctive cha-
racteristic between vegetables and animals, appear to me equal-
ly irrational and visionary with the late enthusiastic pursuits of
the deluded alchemists, after the philosopher's stone, or their
more chimerical researches after their flattering panacea.
Why then should man, presumptuous man ! attempt the es-
tablishment of an essential distinction between physical bodies,
where wiser nature acknowledges none !
2 III.

48 MOTION OF THE BLOOD.
III. The natural functions constitute the third
class. These are subservient to the nourishment
of the body.
IV. The fourth and last class consists of the ge-
nital functions, which are destined for, and employ-
ed in the propagation of the species.
Let us now consider each class of functions in
order, beginning with the vital.
SECT. VI.
OF THE MOTION OF THE BLOOD IN GENERAL.
§ 64.
THE blood as we have already seen, af-
fords the primary origin to the principal parts of
the body, and continues afterwards to convey to
them uniform and perpetual supplies of nourish-
ment, and ought therefore, with a very few ex-
ceptions (§ 5.) to be distributed far and wide,
through even the most subtle and distant recesses
of the whole body. That such a minute distribu-
tion actually takes place, we learn not only from
a fine injection of the vessels, but also from every
day's experience, from which it appears that very
I few 

MOTION OF THE BLOOD. 4
few parts of the body can be punctured with the
point of the smallest pin without the occurrence
of a greater or less hemorrhagy.
This vital liquid does not, as was the opinion
of the ancients, flow and ebb like the waves of
Euripus*, through channels of the same nature
and order, but is so moved onward in an orbit,
or circulates, as they express it, in such a manner,
as to be carried from the heart, by means of the
arteries, to every part of the body ; and being
there taken up by the veins, conveyed back again
by them to the same original fountain, the heart.
§ 66.
After a few, and those very indefinite, expres-
sions † of his predecessors, William Harvey esta-
* A narrow arm of the sea, extending between Bœotia and
Eubœa, said to ebb and flow seven times during each diurnal
revolution of the earth, or each term of 24 hours. In this
extraordinary portion of sea, Aristotle, that celebrated anci-
ent philosopher, is falsely reported to have drowned himself,
because he was not able to develope the cause of the constant
flux and reflux of its waters. C. C.
† The unfortunate Servetus, and that truly illustrious cha-
racter Andr. Cœsalpinus, appear to have advanced nearer to a
true knowledge of the genuine circulation of the blood, than
any of the other physiological writers who are commonly
enumerated in the same class.
VOL I. D It

50 MOTION OF THE BLOOD.
blished, in a manner tolerably conclusive, the cir-
culation of the blood, in a small but immortal
work published in the year 1628.
In process of time, however, every shadow of
doubt on this subject was removed. This was
ejected chiefly by frequent recourse to actual and
simple observations with the microscope ; but in
part also by injections of wax and other substances
into the arteries, which were seen pairing again
to the heart by the route of the veins ; and, fur-
ther, by the elegant and sublime experiment of
It may not be improper on the present occasion to advert
to a remarkable clause in the writings of Servetus, contained
in a physiological dissertation, which he included in his cele-
brated and very scarce work, that occasioned the death of its
illustrious author. The work is entitled " Restitutio Christi-
anismi," &c. (Viennæ Allobrog.) 1553-8. The dissertation
particularly alluded to, is contained in the fifth book of the
abovementioned work, " de trinitate divina, in quo agitur de
spiritu sancto" in which we are presented with the following
words, " Vitalis est spiritus qui per anastomoses ab arteriis com-
municatur venis, in quibus dicitur naturalis."
But from the memorable problem of Cœsalpinus, " de ve-
nis ultra vinculum tumescentibus, non citra," it appears obvious
as the blaze of day, that that truly illustrious physiologist
trod on the very confines of a complete knowledge of the
circulation of the blood. See his " Quæstionum medica-
rum," L. II. quæst. 17. page 234.
transfusing 

MOTION OF THE BLOOD. 51
transfusing the blood of one living animal into
another, or into a human subject; as also by vari-
ous other experiments which may be performed
on animals in a living state.
§ 67.
What should be esteemed the definite standard
of the celerity of this motion, in a healthy human
subject, we are not well able to determine. In
this respect there is not only a difference between
one subject and another, but there also occurs a
great variety relating to this point, arising from
the difference of ages : there indeed exists a dif-
ference in the celerity of the blood's motion, even
in the different parts of the same body.
Finally, the venous blood appears to glide on
more slowly than the arterial; and when flowing
through the trunks of vessels, its motion is more
rapid than when passing their smaller ramifica-
tions. Former physiologists, however, have not-
withstanding exaggerated these several diversities,
in the celerity of the blood's motion, beyond their
natural magnitude.
The common conclusion, however, on this sub-
ject is, that the blood, flowing through the aorta
with its mean velocity, passes over a distance of
about eight inches during the space of one pulsa-
D 2 tion ; 

52 MOTION OF THE BLOOD.
tion ; at which rate it would travel about fifty feet
in the first minute of time.
§ 68.
The globules of the cruor appear to revolve on
their axes or centres of motion ; and it is said that
the same are propelled forward with greater velo-
city than the other constituent parts of the blood.
I know not whether this conclusion be drawn
from actual experiment, or whether it be only an
inference from an absurd application of the com-
mon laws of hydraulics to the circulation of the
blood : I call the application absurd, because it is
certainly the very summit of folly, to attempt to
recount for that motion of a vital fluid, by which
it is carried through the living canals of an ani-
mated system, on the purely mechanical principles
by which water is forced through hydraulic ma-
chines.— As to myself, I must acknowledge I have
never been so fortunate as to be favoured with
a view of this prerogaitve or precession of the
globules.
§ 69.
I am fully persuaded, that those globules only
glide forward, suspended or swimming in the fluid
formed by the other constituent parts of the blood,
but that they do not at the same time rotate on
their own axes at all. To conclude, it is not
fully 

MOTION OF THE BLOOD. 53
fully and clearly ascertained, that the blood, be-
sides its progressive motion, of which we are now
speaking, is also subjected to one of a different
kind, called an intestine motion ; although there
can be no doubt, but that the elementary parts of
the blood may be occasionally affected in their
arrangement and combination, when they are
tumultuously agitated in consequence of the im-
mensely varied directions, the minute divisions and
numerous anastomoses of the vessels through which
they pass.
§ 70.
Thus much we thought proper to advance on
the motion of the blood in general. Previously
to our entering on a more close and minute con-
sideration of this subject, we think it best to treat
of the vessels in which the blood is contained, and
also to consider with attention the energies, by
which these vessels are animated, and fitted both
to receive and again propel the blood.
D3 SECT. 

54 OF THE ARTERIES.
SECT. VII.
OF THE ARTERIES.
§ 71.
THE vessels which receive the blood
immediately from the heart, and convey it to all
the different and minute parts of the body, are
called arteries.
In their collective or aggregate dimensions, they
are less capacious than the veins; but their texture
is far more solid, more compact, very elastic, and,
as appears, from the experiments of Wintringham,
remarkably strong.
§ 72.
They are composed of three membranous strata,
or coats.
I. Of an external, which Haller called a true
cellular coat, Albinus a nervous, Vesalius a carti-
laginous, others a tendinous, &c. It consists of
condensed cellular membrane, externally more lax,
but becoming by degrees more compact, as you
advance nearer to its internal surface, where it
is overspread with numerous small blood vessels.
To 

OF THE ARTERIES. 55
To this coat the artery appears to be chiefly in-
debted for its tone and elasticity.
II. The second or middle stratum, is composed
of transverse fibres, assuming a lunated or falciform
figure and direction ; its substance has a fleshy ap-
pearance, from whence it has been, called the
muscular coat, and in it the vital energy of the
arteries appears in a very particular manner, to
reside.
III. The last and most internal coat, is a mem-
brane of an extremely smooth and polished surface,
which serves as a lining to the cavity of the artery.
In the trunks and larger branches of the arte-
ries, these coats may be distinctly observed ; but
they are less evident in the more minute ramifica-
tions.
§ 73.
All the arterial branches in the human body
take their origin from either one or the other of
two leading trunks.
The first of these trunks is the pulmonary artery,
which, rising from the anterior ventricle of the
heart, passes into the lungs.
D4 The 

56 OF THE ARTERIES.
The second is the aorta, which rises from the
posterior ventricle of the heart, and shoots its
ramifications into every part of the system.
These trunks are divided into branches, which
again undergo farther and more minute subdi-
visions,
§ 74.
An opinion has been conceived and propa-
gated as an established truth, that, throughout
the whole sanguiferous system, the aggregate capa-
city of all the branches, taken together, is superior
to that of the trunk from which such branches
directly originate. I fear, however, that the au-
thors of this opinion have expressed themselves
on this subject in terms by far too general, and
have sometimes even confounded the measure of
the diameter of vessels, with that of their area. In
my investigations and inquiries on this subject, I
did not trust to the result of a single experiment,
nor did I confine my experiments to vessels filled
with wax, which, however improper, were the
only kind used by some celebrated physiologists,
in their attempts to ascertain the matter now under
consideration ; but, as the nature and importance
of the subject evidently demanded, I made my
experiments and observations on the sound and
unaltered vessels of subjects recently dead. I took,
for 

OF THE ARTERIES. 57
for example, that nameless trunk from which the
right carotid an subclavian arteries diverge as
branches, and also the brachial trunk, together
with its branches, the radial and cubital arteries,
and having formed a rectangular triangle, from
the diameter of the trunk and the diameters of its
appended ramifications, I found, from the well
known theorem of Pythagoras, that the Square
of the hypothenuse was equal to the sum of the
squares of the base and perpendicular.
Indeed, in arteries of the smallest orders, Haller
himself acknowledged that the capacity of the
trunks is greater than that of their ramifications ;
so that, at least, the common calculation does not
apply universally, but, (if it be indeed ever admis-
sible), must be restricted to a very few orders of
vessels.
§ 75.
Each trunk and ramification, separately consi-
dered, have been commonly believed to possess
a conical figure, the base, or that part next to
the heart, being supposed mere capacious than
the opposite extremity. This opinion appears
however to be hypothetical : for, whoever will
take the trouble of examining the arteries with
accuracy and attention, will find their figure to be
perfectly cylindrical:, indeed, on the other hand,
there 

58 OF THE ARTERIES.
there are not wanting instances of some arteries
which in their progress rather widen and expand,
such, for example, are the mammariæ internæ, or
internal mammaries, and even the arch of the
aorta itself is more contracted at its base than at
its apex or top. All arteries, especially those of
the larger orders, appear to be a little dilated and
enlarged, just before their division into branches,
§ 76.
The number of orders, formed by the divisions
of the main arterial trunk into the progressive
series of uniformly decreasing ramifications, from
its first origin at the heart, to its final termination
in the extreme capillaries, cannot possibly be uni-
versally ascertained and established as a general
and unvarying result. The truth of this position
will be obvious to any one who considers, that in
the different parts of the body, especially in the
viscera, the arteries are subject to great variety
with respect to their divisions ; and that, on this
account, they sometimes form more, sometimes
fewer orders of vessels, previously to their sepa-
ration into evanescent capillaries.
Hence the disagreement of authors who have
attempted to amuse themselves with calculations
of this kind. Thus, for example, Keil estimated
the number of the orders of arteries at fifty, while
Haller 

OF THE ARTERIES. 59
Haller contended that they amount to no more
than twenty.
§ 77.
After numerous divisions of this kind, and va-
rious anastomoses, by which the neighbouring
branches of arteries communicate with each other,
they at length arrive at their final terminations,
which are completely continuous with, or which
fairly open into, the origins of veins ; fo that,
their route being uninterrupted, they are reflected
from extremities that can scarcely be discerned,
and thus converted into those returning vessels, by
which the blood, lately arterial, but now become
venous, is conveyed back again to the heart.
§ 78.
But although this complete continuity of the
arteries and veins be so extremely evident in nu-
merous parts of the body, as to be obvious even
to the naked eye, yet it still remains a matter of
doubt, whether this be the only and exclusive
mode, in which arteries communicate with veins,
or whether there may not be, at least in certain
parts of the system, an intermediate and parenchy-
matous substance, which receives the blood from
the terminations of the arteries, and again depo-
sits it in the incipient mouths of the veins ?
There 

60 OF THE ARTERIES.
There occur certain phenomena, such for ex-
ample, as erections of the penis, and the common
phenomenon of blushing, which render the ex-
istence of such a connecting medium between
those two kinds of vessels, at least not improbable.
§ 79.
There are, again, vessels of a nature evidently
different from those already spoken of, which ap-
pear to arise every where from the smaller arte-
rial branches; these vessels consist chiefly of two
kinds, namely, the serous, which are so narrow as
not to be able in a healthy subject to admit the
globules of the cruor, but only to receive the
thinner fluid or vehicle in which those globules
swim (§ 69.) ; and the secretory, which do not
appear to attract any thing from the mass of arte-
rial blood, but such specific fluids as are destined
for secretion (§ 4.)
§ 80.
With regard to the former kind of vessels,
which we denominated serous, it is necessary to
observe, that we do not mean by them the imagi-
nary orders of yellow and of white vessels, spoken
of by Boerhaave, which appear to have been fan-
cifully conceived, in conformity to the account
given by Leeuwenhoek of his equally imaginary
sixfold conformation of the globules of the blood:
neither 

OF THE ARTERIES. 61
neither do we mean the neuro-lymphatic vessels
of Vieussen and Ferrein, of which those gentle-
men supposed the viscera to be in a great measure
composed ; but which do not indeed appear to be
any better founded than the preceding conjectures
of Boerhaave and Leeuwenhoek.
By the serous we mean those colourless vessels
which are never visible, unless in certain cases of
violent inflammation, where the impetus of the
blood is very powerful; and indeed in some parts
of the body, even this energetic process of nature
is not of itself sufficiently powerful to bring them
into view, unless they be still farther dilated by
means of an anatomical syphon or injector : of this
latter description are, for example, the vessels of
the cornea, which can scarcely ever be filled with
wax, unless in the dead bodies of such subjects as
have died while labouring under a violent inflam-
mation of the eyes.
§ 81.
The secretory vessels, on the other hand, appear
to be different from those, and belong chiefly to
the secreting viscera and conglomerate glands;
they can also be traced by means of a very subtle
injection, which, for instance, when thrown with
force into the artery of the parotid gland, flows
out and escapes through the duct of Stenonius.
But

62 OF THE VEINS.
But on these vessels we will have a stated oppor-
tunity of being more pointed and particular in a
subsequent section.
SECT. VIII.
OF THE VEINS WHICH CARRY BLOOD.
§ 82.
THAT blood, which, by means of the
arteries has been distributed throughout every
part of the system, must be conveyed back again
to the heart through the medium of the veins.
These vessels differ very widely from, the arte-
ries, both in their functions and structure : to this,
however, veins of the smallest orders form an ex-
ception, as their structure does not differ from that
of arteries of the same magnitude in so wide and
obvious a degree.
§83.
The veins (if we except the pulmonary system)
are more capacious in their collective or aggregate
dimensions than the arteries ; their ramifications
are also more numerous ; they are much more ir-
regular in their courses and modes of ramifying ;
their 

OF THE VEINS. 63
their texture is also much softer than that of the
arteries ; they are far less elastic, but nevertheless
extremely tenacious, and capable of wonderful ex-
pansion.
§ 85.
Their coats are considerably thinner than those
of the arteries; whence the blood which they
contain appears in some measure through them ;
they are also less numerous, being no more than
a certain cellular covering, somewhat resembling
what has been called the nervous coat of the ar-
teries, and an internal membrane of a very exqui-
site polish, similar to that with which the arteries
are lined.
No part of the venous system is furnished with
muscular fibres, except the larger trunks near the
heart.
§86.
In by far the greater number of the larger
veins, such, for example, as exceed in their dia-
meter the twelfth part of an inch, this internal
membrane forms, by its foldings, an immense num-
ber of valves of the most beautiful structure, ex-
ceedingly pliant or moveable, and exhibiting the
appearance of small sacks : they are, for the most
part, simple and alone, frequently however, ar-
I ranged 

64 OF THE VEINS.
ranged in pairs, and sometimes in triplets ; and
are so situated and disposed, that the bottom of
the little sack points to the origin of the vein,
while its mouth or orifice opens, and is directed
towards the heart.
Those small valves are, nevertheless, wanting in
the veins of certain parts, as in those of the ence-
phalon, the lungs, &c. and in the whole system of
the vena potarum.
§ 87.
The small ramifications of the veins (which
would, indeed, with more propriety be called their
radicles or little roots) form, by their junctions,
larger branches, and these unite finally into six
leading trunks; viz. the two venæ cavæ, one cal-
led the superior, the other the inferior, and the
four trunks of the pulmonary vein.
The vena portarum alone exhibits one pheno-
menon peculiar to itself. The trunk of that vein,
on entering the liver is, after the manner of an
artery, immediately divided into branches, the
extreme ramifications of which become, at length,
radicles to the inferior cava, and finally lose them-
selves in the bosom of that trunk.
I § 88. 

OF THE VEINS. 65
§ 88.
We need not, on the present occasion, again
advert to the common, and by far too general,
opinion, that the areas of the branches are more
capacious than the area of the trunk from which
they rise, nor yet to that respecting the conical
figure of single vessels, as what was said on those
subjects, when treating of the arteries (§ 74, 75.),
will apply with sufficient precision to the veins.
There are also among the veins, a few examples
of vessels being more capacious at a more remote
distance from the heart; such, for instance, is the
vena poplitea, where it passes between the condyls
of the of femoris.
* What has been already said, with regard to the
final terminations oSthe arteries (§ 77, 78, 80.),
may, by making such obvious and necessary
changes, as are adapted to the different nature
and circumstances of our subject, be fitly applied
to the origins of the veins.
VOL. I. E SECT.

66 OF THE HEART.
SECT. IX.
OF THE HEART.
§ 89. 
THERE exists, as we have already had 
occasion to observe (§ 65), a two-fold communi-
cation between the arteries and veins: one, for
instance, at the minute extremities of each kind of 
vessels (§ 77) ; and the other at the heart, their 
common fountain, in which the leading trunks of 
the whole sanguiferous system meet.
§ 90.
The heart is, as it were, the first active organ 
and moving spring of the whole human machine, 
as it is by the perpetual and truly astonishing
energy of this body, that the most important vital
function, namely, the circulation of the blood, is
performed, from so early a date of our existence, 
as the fourth week after conception, down to the 
closing period of transient life.
§ 91.
This active organ, by its alternate dilatation
and contraction, first receives and again ejects the
blood in the following manner. Into the anterior 
venous sinus, and its appendage, the anterior auri-
cle 

OF THE HEART 67
cle of the heart, the blood is conveyed from the!
whole body, by means of the two venæ cavæ, viz.
the superior and inferior, and likewise from the
substance of the heart itself, by means of the coro-
nary veins, the common orifice of which is fur-
nished with a valve of a peculiar structure; and
from this auricle, it is again conducted into the
corresponding ventricle of the same side.
§ 92.
From this anterior ventricle (formerly called
the right ventricle, in conformity to the situation
of the heart in brutes) the blood is thrown into
the lungs through the pulmonary artery, which
was called by the ancients vena arteriosa; from
thence, by the four pulmonary veins, called in
former times arteriæ venosæ, it is conducted into
a common sinus, formed by their conflux, and
thence again into the corresponding auricle; these
were once called the left, but are now more pro-
perly named the posterior, sinus and auricle.
§ 93.
From the posterior auricle it passes on to the
ventricle of the same side, from whence it is distri-
buted, by means of the aorta, through the whole
arterial system appropriated to the other parts of
the body, and by the coronary arteries, through
the substance of the heart itself.
E 2 § 94.

68 OF THE HEART.
§ 94.
The blood having passed from the extreme and
ultimate branches of the arterial, into the incipient
radicles of the venous system, re-enters the two
venæ cavæ, (while that from the coronary arteries
is also returned by veins of the same name), and
thus the whole collective volume resumes again, 
and incessantly continues, the same circuitous route
already described.
§ 95.
This circular and regularly progressive motion
of the blood through the cavities of the heart, is 
powerfully directed, and the regurgitations of that 
fluid are completely prevented, by means of small
valves, which surround and serve as portals to the
principal avenues which lead to the heart. These
valves are situated on the margins, or extreme lips, 
of the ventricles which are adjacent to, and look 
towards, their corresponding sinuses, and also at 
the mouths of the two great arterial canals leading
out of those ventricles. 
§ 96.
Thus a small venous ring or tendon, which
forms a partition between the anterior sinus and 
ventricle, descending into the cavity of the latter,
separates into three small valves of a tendinous
appearance, each one of which was formerly be- 
lieved to divide again into three apices or points, 
from 

OF THE HEART. 69
from whence they received the name of valvulæ
triglochines or tricuspides. These valves are con-
nected at their points to fleshy columns, common-
ly called musculi papillares.
§ 97.
In like manner another small ring of the same
kind, which constitutes a partition between the
posterior sinus and ventricle, is also divided into
two small valves, which, from a certain supposed
resemblance to a sacerdotal mitre, have been called
valvulæ mitrales,
§98.
At the entrance into the pulmonary artery, as
also at the mouth of the aorta, are situated, in an
annular or circular position, three valves much
smaller indeed than those already described, but
of a very elegant and beautiful figure and appear-
ance, and furnished with fleshy fibres; these have
been called valvulæ semilunares or sigmoides.
§ 99.
Now it evidently appears, that by means of
these different kinds of small valves, sufficient pro-
vision is made against the irregular, confused and
retrograde movement of the blood. They easily
yield, and afford a passage to the blood when ad-
vancing regularly forward in the established course
E 3 of 

70 OF THE HEART.
of its circulation. But they prevent the regurgi-
tation of this fluid, by becoming, in consequence
of its refluent effort, fully expanded like the swell-
ing of a well-filled sail, and thus completely closing
the orifices round which they are arranged.
§ 100.
The valve of Eustachius which, in the fœtal
state, is stretched like a curtain across the mouth
of the ascending cava, becomes after birth (sooner
or later in different Subjects) so gradually oblite-
rated for the most part, as to be rendered wholly
unfit for the execution of its former functions ;
neither indeed does the system stand any longer in
need of it, as a passage is now opened and prepa-
red for the blood through the lungs, and its re-
turn from those viscera prevented by the semilu-
nar valves already spoken of, and as each subse-
quent column of blood, pressing from behind, must
pursue the same route with that immediately pre-
ceding it. But as it does sometimes notwithstand-
ing happen, that the passage of the blood from
the right side of the heart into the lungs is by
some means obstructed, we then learn from the
preternatural pulsation observable in the superior
cava, that the blood is repelled in a retrograde di-
rection from the right sinus into the two adjoining
great venous trunks.
§ 100

OF THE HEART. 71
§ 101.
It is a point of controversy, whether or not the
semilunar valves suffer the ventricles to be perfect-
ly and completely evacuated, or whether they do
not rather by means of their expansion intercept
a part of the blood in its escape from those cavi-
ties, and thus force it to take in some measure a re-
trograde course.
Observations made on frogs, and even on the
minute heart of the nascent chick, prove that in 
those animals the heart is indeed completely eva-
cuated ; but whether or not the same thing takes
place in man himself, when in a sound state of
health, is not yet clearly ascertained ; if, however,
it be admissible, in physiological discussions to spe-
culate and draw conclusions from the structure and
mechanism of those valves themselves, as they ap-
pear on the dissection of the heart, the contrary
opinion appears the most probable.
§ 102.
The texture of the heart is altogether singular,
and peculiar to that organ. It is indeed fleshy,
but remarkably close and compact, and widely dif-
ferent from the common constitution and appear-
ance of muscles.
E 4 It 

72 OF THE HEART.
It is composed of small bundles of fibres, more
or less oblique, frequently ramifying in a singular
manner, contorted and wound spirally in diversi-
fied and truly strange directions; these fibres lie
over, and rest on, each other in certain orders of
strata, they are intermingled and closely knit to-
gether in the septum which separates the two ven-
tricles, and are fattened and firmly connected at
the basis of those ventricles by four cartalaginous
rings or bands, which (according to the accurate
unravelling and developement of the whole fibrous
texture of the heart, lately executed by the inde-
fatigable and illustrious Wolff), appear to serve as
a stay and support to the fleshy structure of the
ventricles, and also to separate and distinguish it
from the fibres of the sinuses.
§ 103.
Those fleshy fibres are every where overspread
with an infinitude of small nervous ramifications
of extreme softness, but they are more particularly
supplied with such an immense apparatus of blood
vessels, arising from, and belonging to, the coro-
nary arteries and veins, that Ruysch has declared
in his writings, that the whole fabric of the heart
appears to be composed solely of sanguiferous
tubes.
§ 104.

OF THE HEART. 73
§ 104.
By means of the foregoing structure (§ 90.
seq.) and texture (§ 101. seq.) the heart is fitted
for the performance of those perpetual and uni-
formly equable movements, which return in such
general order, that the preliminary appendices
and ventricles themselves, are alternately contrac-
ted and relaxed, or perform, in alternate times,
those motions, called in physiological language,
systole and diastole.
§ 105.
With such definitude do they preserve this har-
monious order in their routine of contraction and
dilatation, that as soon as the appendices contract
themselves, to propel the blood, returning from
the lungs and venæ cavæ, into the ventricles,
these latter are at the same instant relaxed and
fitted to receive the same advancing wave of
blood ; but in the subsequent and next moment,
when it is the point of time for the ventricles,
new recently filled, to contract and force the blood
into the two arterial trunks, the appendices are
again relaxed, and their mouths rendered patulous
for the purpose of drinking in a fresh tide of ve-
nous blood as it roils on in its usual course.
§ 106. 

74 OF THE HEART.
§106.
This systole of the ventricles, which is supposed
to consume about one third part of the whole time
of the heart's pulsation, is performed in such a
manner, that the exterior sides of those cavities
are approximated and contracted towards the in-
termediate septum which separates the right ven-
tricle from the left; which contraction, especially
if we attend to the conical figure of those cavities,
appears fully sufficient to evacuate them of their
contents.
But besides this approximation of the lateral
parts of the heart towards each other, the apex
of that organ is, during its systolic motion, con-
tracted towards, and brought nearer to its basis;
as has been frequently observed not only in the
inferior animals both of cold*, and warm blood,
but even in man himself, while in a living state†.
* I have not in the live-dissection of any animal discover-
ed the heart more evidently shortened, during its systolic
motion, than in that of coluber natrix or water serpent.
Throughout the forests in the neighbourhood of our city,
this species of serpent may be sometimes found four feet in
length. Having taken one of these animals and subjected it
in a living state to the anatomic knife, I observed that the
length of its heart during the diastolic, exceeded its length
during the systolic motion, at least the space of two lines.
† It does not, however, appear that this diminution of
the longitude of the heart during its systolic motion is an ab-
4 solute 

OF THE HEART. 75
An argument seemingly in favour of a contrary
opinion has been derived from, and founded in,
vulgar experience, from which it appears that the
apex of the heart strikes, during its systolic mo-
tion, against the left mamma or breast, and seems
therefore to be rather elongated than contracted
and shortened; this apparently conclusive argu-
ment will however have no weight with one who
considers, that those sensible percussions or strokes
of the heart are to be attributed as well to the im-
petus of the venous blood rushing into the appen-
dices of that organ, as to that of the arterial blood
forcibly ejected from its ventricles ; by both which
sources of propulsion the whole heart is carried
towards and impinged against that region of the
ribs.
§ 107.
The impetus, which is by this systolic contrac-
tion of the heart imparted to the blood, is com-
solute condition of life. I am led to the adoption of this
opinion from a variety of observations made on the heart of
a duck, in a great portion of which a complete ossification
had taken place. This heart was deposited in my anatomi-
cal collection by my very liberal and worthy friend C. F. Mi-
chaelis, and is marked by completely ossified striæ running
from its base to its apex. On its sides, however, it was still
furnished with fleshy substance sufficient to continue the late-
ral motion of its ventricles., and thus preserve the circulation
of the blood.
municated 

76 OF THE HEART.
municated to the arterial system, receiving the
blood, in such a manner, that every systole of the
heart may be plainly perceived in such arteries of
the other parts of the body as can be felt by the
touch, (of which description are all those that ex-
ceed in their diameters the sixth part of a line),
and likewise in such other arteries as can by any
means whatever have their pulsations rendered
obvious to the senses : this can be easily effected,
for example, in the internal ear or eye, in either
of which a singular kind of motion can be excited
and rendered sensible, which (as well as the same
kind of throbbing or pulsatory motion fo percep-
tible in the other parts of the arterial system) is
called the diastole of the arteries : of this diastolic
motion we shall have an opportunity to speak on
a future occasion, at which time we will take up
the inquiry, whether or not it is to be attributed
solely to the action of the arteries themselves, or
derives its existence from some other source.
§ 108.
In whatever manner this point may be deter-
mined, one thing we learn from experience, the
surest guide to truth, viz. that in a healthy sub-
ject, what is called the pulse of the arteries, is
precisely synchronous with, and perfectly corres-
pondent to, the motions of the heart ; and like-
wise in a morbid intermission of the pulse, the
heart

OF THE HEART. 77
heart and arteries still harmonize in their action,
by ceasing from, and again commencing, motion
at precisely the same moments.
§ 109.
The frequency of the pulsations of the human
heart in a healthy state, is extremely different in
different subjects. This diversity arises principally
from diversity in point of age, but partially also
from other conditions of the system, which at any
and every period of life constitute the health pro-
per to each individual ; so that it is not possible
to ascertain and establish, on this subject, any cer-
tain and definite rule. It may nevertheless be pro-
per to mention the general result of my observa-
tions (made in our own climate) on the frequency
of the pulse in the different periods of human life.
In the first days after birth I have generally
found the pulsations of the heart of the tender in-
fant, while sound asleep, amount to about 140 in
the space of a minute.
At the expiration of the first year, they amount
to 124 in a minute.
At the end of the second year to about 110.
At the end of the third year to about 96, &c.
At 

78 OF THE HEART.
At that period in which the first set of teeth,
usually called the milk-teeth, drop out, the pulsa-
tions of the heart amount to 86 in a minute.
At the age of puberty to about 80.
In the prime of life, or at the period of man-
hood, to about 75.
And to about 60 at the sixtieth year of human
life.
In subjects still farther advanced in years, I have
scarcely found two in whom the number of pulsa-
tions were the same, at the same period of old
age.
§ 110.
All other circumstances being alike, the pulsa-
tions of the heart are more frequent in females
than in males.
If proper and necessary allowance be made for
the habit of body, they are less frequent in men
uncommonly tall, than in such as are rather low.
This circumstance I have ascertained to be a truth
by comparative observations made on the pulses
of dwarfs, and giants or men remarkably large.
§ 111. 

OF THE HEART. 79
§ 111.
On the subject of those varieties in the pulse,
occasioned by extraneous circumstances, vulgarly
called non-naturals, it is necessary to observe, that
a cold climate produces a slow pulse; thus, for
instance, the heart of a Greenlander when in
perfect health, does not pulsate oftner than from
thirty to forty times in a minute.
But it is an observation as common as it is
true, that the pulse becomes more frequent after
the taking in of aliment, and after an emission of
semen. The same effect is also produced on the
pulse by a want of sleep, by bodily exercise, or
by passions of the mind.
§ 112.
The foregoing observations relate to the na-
tural or healthy pulse, in the consideration of
which it seems more consistent, and agreeable to
nature, to direct our views to the heart, as its ex-
clusive source, than to the arteries, on which
physiologists have usually fixed their attention
when engaged in the investigation of this subject.
In this incessant routine, the heart continues its
pulsations, down to the extreme glimmerings of
life's perishable flame ; and even then, all its parts
do not cease from action at the same moment,
but 

80 OF THE HEART.
but it is the prerogative of the right ventricle
with its appendices, the right auricle and sinous,
survive the left ventricle, and its appendices.
This may be sufficiently illustrated in the fol-
lowing manner : After the last act of expiration,
the lungs now in a collapsed state, can no longer
admit the blood to flow through them in its cus-
tomary channel, while at the same time that wave
of blood which they have just returned to the lest
side of the heart, is from thence forceably expel-
led through the aorta, and thus urges forward by
a vis a tergo the advancing column of venous
blood : from this combination and concurrence
of circumstances, the blood returning with preci-
pitation and impetuosity, rushes violently into the
appendices and ventricle on the right side of the
heart, in consequence of which the parietes of
those cavities are thrown into convulsive efforts,
and thus continue to be agitated, for some time,
after the left side of that organ is completely de-
prived of all vital motion.
§ 113.
From a knowledge of this fact, viz. that
during the last vital efforts of declining nature,
the blood is propelled into the cavities on the
right side of the heart, we deduce, with the ut-
most ease, the cause of that state of depletion in
I which 

OF THE HEART. 81
which the larger arteries are found after death.
To the same cause also Weiss, and after him the
illustrious Sabatier, were desirous of attributing
the superior size of the cavities on the right, to
that of those on the left, side of the heart, espe-
cially in the corpse of an adult subject.
§ 114.
The whole of this motion of the heart, which
has been the subject of the preceding observa-
tions, is to a very considerable degree limited and
directed by the pericardium, in which the heart
loosely hangs, and by which it is completely en-
closed as in the walls of a prison.
The pericardium is a membranous sac, consid-
erably capacious, and accommodated to the figure
of the heart which it encloses. It takes its origin
from the membranes constituting the mediastinum,
and although, from its fineness, it may appear some-
what tender, yet we learn from the experiments
of Wintringham, that it is so very tenacious and
firm, as far to exceed in strength all other mem-
branes of a similar nature in the human body,
That the pericardium is a part of the first
importance in the animal economy, we safely
infer from this single circumstance, namely, that
throughout all classes of animals possessing red
VOL. I. F blood, 

82 OF THE HEART.
blood, it is found as constantly and uniformly ex-
isting as the heart itself; and records do not fur-
nish more than one or two examples of the human
heart having been found completely destitute of a
pericardium. These singular examples of such an
unnatural state of the heart are recorded in the
writings of Dinkier.
§ 115.
The internal surface of the pericardium is kept
constantly humid by a dew-like serous effusion,
which appears to exhale from the small arteries
of the heart itself.
In like manner a fluid, of a similar nature, ap-
pears to transude into the very cavities of the
heart, and to moisten and lubricate their surround-
ing parietes or walls.
In either case the effusion during the healthy
state of the part is of a serous nature, and not ac-
companied by any real lymph, unless the heart be
labouring under inflammation ; but when this or-
gan becomes the seat of an inflammatory affection,
then genuine lymph transudes, giving rise, on the
external superficies of the heart, to fine filaments
of a hair-like appearance, together with those
preternatural portions of cellular membrane,
which in such cases connect the heart to the
pericardium, 

POWERS, &c. 83
pericardium, but on the interior surfaces of the
cavities themselves producing excrescences of a
truly polypous nature. (§ 19.)
SECT. X.
OF THE POWERS BY WHICH THE BLOOD IS
KEPT IN MOTION.
§ 116.
HAVING thus completed the consid-
eration of the organs in which the blood is con-
tained, we now pass on to take a view of the
powers, by which those organs are qualified and
fully prepared to keep that vital fluid in motion.
Let us, in the first place, take an attentive and
accurate survey of those powers which reside in
the heart itself, and which ought, without doubt,
to be considered as by far the most active and es-
sential in the great business of circulation: we
will then proceed to consider what may be called
the secondary and assistant powers, which we will
also find of high importance in the animal econo-
my, from the concurrent and effective aid which
they afford to the action of the heart.
F2 § 117.

84 POWERS WHICH KEEP
§ 117.
It will at first view appear obvious to even the
most superficial observer, that it is a matter of
Herculean difficulty indeed, either to ascertain by
accurate calculation the force of action exerted
by the heart, or to determine with precision the
quantity of blood thrown into the aorta by that
organ at each pulsation ; neither will the specula-
tive physiologist find himself beset with difficulties
of less moment, when he attempts to ascertain and
establish with definitude, either the distance to
which each projected wave of blood is carried by
the impetus it receives from the heart alone, or
yet the celerity with which such wave rolls for-
ward ; but he will be surrounded with difficulties,
still encreasing at each advancing step, in his at-
tempts to render a just statement and accurate ac-
count of all such obstacles as oppose, and thus
greatly diminish the effects of the force exerted
by the heart, in its action on the circulating mass
of fluids.
§ 118.
A certain estimation may nevertheless be formed
of the power of the heart, by collecting and com-
paring the most probable conjectures which have
appeared on the above points of physiological spe-
culation. Thus for instance, if we suppose the
whole mass of blood to amount at a mean rate to
33

85 THE BLOOD IN MOTION. 
33 pounds, i. e. 396 ounces (§ 23), and estimate
the number of pulsations at 75 in a minute, i. e.
4500 every hour (§ 109); and further, if we
adopt the opinion that at each systole the left ven-
tricle ejects two ounces of blood, it will then fol-
low, that during the course of every hour the
weight of the whole volume of blood makes 22 3/4
complete transitions through the heart. We may
also form a tolerable conception and estimation
of the impetus with which the circulating blood
is propelled from the left ventricle of the heart,
by observing with what astonishing violence, and
to what a considerable height, the blood spouts
from one of the larger arteries when wounded in
the neighbourhood of the heart. Thus, from
the wounded carotid of an adult subject, I have
seen the blood, during a few of the first contrac-
tions of the heart after the accident, mount in
jets to the height of at least five feet.
§ 119.
But when we institute an enquiry for the dis-
covery of those unfailing fountains or springs,
which supply the heart with a force so powerful,
and at the same time so uninterrupted and lasting,
that which first attracts our attention, as being
foremost both in point of time and importance is
its irritability, (§ 44). This vital energy, as has
been already evinced (§ 90), is much longer pos-
F3 sessed 


86 POWERS WHICH KEEP
sessed by the heart, than by any other muscular
part in the whole human body.
That the parietes, or walls themseves of the
cavities, are irritated and excited to contract by
reiterated impressions from the circulating waves
of blood, is manifest from a well known experiment
of the illustrious Haller. From this celebrated
experiment, of that indefatigable physiologist and
acute philosopher, it appears, that he could at
pleasure grant, either to the right or left side of
the heart, the prerogative of a more protracted
vital motion, (i. e. of longer life) accordingly as
he first deprived the one side or the other of its
peculiar stimulus, the blood*.
§ 120.
When the proportional quantity of the blood
is well adjusted to the size of the containing vessels,
and its quality uncontaminated by any morbid
change, its action on the heart, and the re-action
of that organ again on the blood, proceed with
such an equable, regular and happy facility, that,
when in a state of rest, we are scarcely sensible of
the circulation of this vital fluid, which is the kind
and constant dispenser of life and vigour to every
part of our bodies.
* See Haller " De motu cordis a stimulo nato," in
Commentar. Soc. Scient. Goettingens, tom. i.
But 

87 THE BLOOD IN MOTION. 
But is the circulating volume of blood be either
too abundant, or preternaturally scanty, but espe-
cially if this vital fluid be contaminated by the
admixture of any foreign substance, as noxious
miasmata, air in an elastic state, or poisons in-
jected into the veins, &c. the heart, either roused
immediately into excessive action, or depressed to
the opposite extreme of prostration and debility,
continues no longer fit for the salutary discharge
of its important function, but falls into motions
convulsive, irregular, and very widely different
from the equable tenor of its healthy action. Fo-
reign substances of the same kind, as air blown
into the veins, &c. are also sometimes able to
rouse again, and excite to motion, the heart of an
animal recently dead.
§ 121.
It has been a point of controversy, even in very
modern times, whether this extreme irritability of
the heart be essentially inherent in its own sub-
stance, or if it be not rather adventitious, and de-
rived, as some celebrated characters would induce
the world to believe, from the mysterious influence
of the nerves? We will hereafter have a fit oppor-
tunity of declaring our sentiments respecting the
whole of this controversy, when we come to con-
sider the doctrine of muscular irritability, under
which head, this subject of inquiry most naturally
F4 falls. 


88 POWERS WHICH KEEP
falls. On the present occasion it may suffice to
observe, that I am daily more and more convinced,
that irritability is a species of vital energy altoge-
ther peculiar in its nature, belonging exclusively
to muscular fibres, and completely distinct from
the vis nervea (§ 34, 45.) But, on the other
hand, it is no less evident and incontrovertible,
that the nerves do also possess a very powerful in-
fluence and command over the action of the heart:
this we learn, as well from the peculiar habit and
appearance of the cardiac nerves, from their soft-
ness, their defect of covering, and their singular
disposition and arrangement, as from the astonish-
ing consent of the heart with by far the greater
number of the functions of the human body, even
with those of the most opposite nature. In testi-
mony of the reality of this consent, it may be
sufficient barely to mention, the sudden and tran-
sient sympathy which, even in a healthy subject,
exists between all the passions of the mind and
the heart, together with that, which, in a great
many species of disease, manifests itself between
this organ and the primæ viæ.
§ 122.
Bur, besides those vital energies of the heart,
it possesses also another power, arising out of its
mechanical structure, which appears to contribute
not a little towards carrying on the circulation of
the 


89 THE BLOOD IN MOTION. 
the blood. The cavities of this organ being
closely contracted, in the time of its systole, and
the blood by this means completely expelled, a
vacuum is thus produced, into which, on the prin-
ciples of the well known law of derivation, the
neighbouring blood must of necessity flow; for, as
the valves prevent the regurgitation of the wave
just ejected, it follows of course, that the cavities
of the heart must then drink in, and swallow down,
with rapidity, the blood advancing in the trunks
of the veins.
§ 123.
We proceed now to enquire, whether or not,
any of the other organs through which the blood
passes, besides the heart itself, are furnished with
powers contributary to the continuance of the
circulation of that fluid. Judging from first prin-
ciples, or a priori, as it is termed, we are led to
suspect that such powers do exist; for it appears
hardly probable, that the wisdom of nature has
entrusted so important a function, on which the
life of sanguiferous animals immediately depends,
to one organ only, the faults and defects of which
might, in such case, with too much facility, be
attended with fatal consequences. But, reasoning
a posteriori, as they term it, i. e. from actual ob-
servations, made on the animal economy, we are
furnished with numerous facts sufficient to establish,
beyond 

90 POWERS WHICH KEEP
beyond a doubt, the existence of such powers,
which we may therefore term secondary powers,
and which are able, not only to aid the action of
the heart, but, in some cases, to compensate for
almost the complete absence of the influence of
that important organ. A striking instance of this
nature, is the continued motion of the blood, in
certain parts of the body, on which the power of
the heart can have but very little effect, if indeed
it can extend to them at all: this phenomenon is
observable, as well in the venous system of the
liver, as in the placenta of the uterus; not to
mention numerous instances of fœtuses having
been born, without the smallest vestige of a heart.
§ 124.
Of these secondary powers, the first to be men-
tioned is, the functions of the arteries, the influ-
ence of which, in promoting and continuing the
circulation of the blood, appears to be, indeed,
very considerable; although the true principles
and mode of their action, on this fluid, have not
yet been fully developed and established.
Speaking in general terms, there exists a very
considerable resemblance between the arteries and
the heart itself: that the arteries, for example,
have a muscular coat, is a fact of the utmost pub-
licity (§ 72.)
That 

91 THE BLOOD IN MOTION. 
That they also possess irritability, has been very
generally known, since the famous experiments of
the illustrious Verschuir.
And, further, as the aspect or disposition of the
cardiac nerves on the heart itself is truly singular,
thus also the larger branches of the arteries are,
here and there, surrounded with astonishing reti-
cular intertextures of soft nerves.
§ 125.
Finally, It is well known to every one that the
arteries pulsate, and that indeed with such vehe-
mence and force, that if we suffer one of our legs
to lie over the other knee, the pulsations of the
popliteal artery are sufficient to elevate in a sub-
fultory manner, the superincumbent leg not only
alone, but even with a very considerable weight
appended to it. Indeed for a long time past, both
a systolic contraction and diastolic relaxation have
been attributed to the arteries, which motions
have been said to correspond and harmonize with
the alternate contractions and dilatations of the
ventircles of the heart.
Though the truth of this last proposition is
generally believed to be established and confirmed
by the simple testimony of the senses themselves,
the subject is nevertheless still embarrassed with
various 
 

92 POWERS WHICH KEEP
various doubts and difficulties: these difficulties
immediately rise to view, when it is asked,
whether this vibrating or pulsatory motion,
which is felt on examination by the finger, is to
be attributed to the inherent energy of the ar-
teries, or to the impulse of the heart; and
whether the whole motion of the arteries does
not depend solely on the impetus with which the
blood is projected into the aorta, and thus im-
pinges against the sides of that tube, and its rami-
fications?
Dissections of living animals have not been suf-
ficient to decide this controversy. For it some-
times happens that during the live-dissections of
warm blooded animals you may discover the lar-
ger arteries pulsating, while at other times again
they appear in a state of complete rest. In man
himself, while in the enjoyment of vitality, I had
once an occasional opportunity of observing the
neighbouring trunks of the aorta and pulmonary
artery, to be perfectly destitute of all motion;
but it should not be forgotten, that this phenome-
non appeared in a case of monstrous or preterna-
tural formation of the parts. There are also ar-
teries which we sometimes feel in a state of violent
pulsation, and which we nevertheless know, from
anatomy, are, in consequence of their situation,
almost immoveable; of this we have an example
in 

93 THE BLOOD IN MOTION. 
in the cerebral carotid, where it passes through
the canal of the os petrosum.
§ 126.
When all circumstances relative to this subject
are impartially weighed and dispassionately consi-
dered, this appears to be the result, viz. that the
diastole of the larger arteries takes place in conse-
quence of their peculiar nature, and is to be attri-
buted to the impetus of the blood rushing for-
cibly into them, and expanding their coats or tu-
nics, which, by means of their elasticity, imme-
diately return again to their natural dimensions.
To the same impulse also should be attributed
that lateral or curving motion of their axes,
which may frequently be observed in the larger
arteries when they run in a serpentine direction,
and lie embedded in soft cellular membrane.
But in a found state of the system, we contend
that the arteries scarcely exhibit any unequivocal
proofs of a true systole, i. e. they do not by a ge-
nuine contraction recede from their natural, to
smaller dimensions, as long as the heart is adequate
to the due performance of its momentous func-
tion; but although it be certain, that the arteries
do not always, yet we acknowledge that they do
sometimes, exhibit and exercise a power of real
contraction: thus for instance, when the heart is
deficient 

94 POWERS WHICH KEEP
deficient in its action in consequence of labouring
under either a morbid ossification, or some other
species of disease, it is probable that then the
duties of this important organ devolve on, and
are discharged by, the arteries, and that the
blood is thus kept in motion by the vital energy
of those animated tubes.
§ 127.
As it has been the decided opinion of several
celebrated physiologists, especially the famous
Whytt, that the powers of the heart cannot pos-
sibly extend their influence to blood-vessels of the
smallest order, as, for example, to the extreme
terminations of the arteries, and to the incipient
radicles of the veins; they have therefore attri-
buted the motion of the blood, in that part of the
system, to a certain oscillatory action of those mi-
nute vessels themselves, by the help of which their
contents are propelled forward: and this same vi-
bratory motion they have also applied, with a
great deal of ingenuity, to explain and demon-
strate the nature of inflammation, &c.
There are indeed a variety of phenomena, as
well physiological, which shall be mentioned when
on the subject of animal heat, as pathological, par-
ticularly observable in spasmodic affections, ac-
companied with fever, which seem to favour the
existence 

95 THE BLOOD IN MOTION.
existence of such a power of oscillatory motion,
although no such motion has ever been actually
observed, even with the assistance of glasses, in
the dissections of living animals.
§ 128.
It yet remains to enquire also after those assist-
ant powers, by which the other parts of the veins,
besides their radicles or incipient roots, are fitted
to complete finally the return of the blood to the
heart. It appears, indeed, at the first view of the
subject, that the veins possess and exert a much
smaller portion of the active vital energies than
the other parts of the sanguiferous system, because
the return of the vital fluid, contained in those
vessels, towards the heart, seems to be owing to
the impetus of the arterial blood urging it on by
a vis a tergo, as well as to the valvular structure
of the veins themselves, which effectually prevents
the blood from regurgitating. That these minute
valves are of the utmost importance in promoting
and continuing the regular and free circulation of
the blood, is satisfactorily demonstrated by the fre-
quent congestions and infarctions, which happen in
those veins that originate in the inferior parts of
the abdominal cavity, and which are entirely de-
stitute of such valves.
But 

96 POWERS WHICH KEEP
But there are nevertheless a variety of argu-
ments which render it probable, that the trunks
of the veins do possess, and actually exert, certain
degrees of the vital energies; as is well exempli-
fied in the veins of the liver, and of the uterine
placenta (§ 123.), &c.
It is also well known to every one, that the ex-
periments first instituted by the illustrious Ver-
schuir, are highly in favour of the existence of a
vital energy in the veins.
And, that the two leading and extreme venous
trunks have a stratum of a true muscular nature,
we have briefly hinted on a former occasion
(§ 84).
§ 129.
These are indeed the leading powers which are
active in promoting the circulation of the blood,
and which derive their origin from the very
structure of the vessels in which this fluid is con-
tained. I say nothing of the manner or degree in
which the motion of this vital liquid is influenced
by weight, attraction, or such other properties as
are possessed by all bodies in common.
I also pass over in silence the more remote and
inconsiderable aids, which, in a human subject after
birth 


97 OF RESPIRATION.
birth, are afforded to the circulation of the blood,
by the exercise of the other functions of the system,
such as respiration, muscular motion, &c.
SECT. XI.
OF RESPIRATION, AND ITS PRIMARY USE.
§ 130.
THE lungs, which are very intimately
connected with the heart, as well from the vicinity
of their situation, as from their uniform intercourse
in the performance of their important function,
are two viscera, large in the human subject after
birth, but of such specific lightness, as to float on
the surface of water. They consist of a paren-
chymatous substance, of a spungy texture, and
even exhibiting somewhat the appearance of foam,
yet still considerably tenacious and strong.
§ 131.
The lungs fill up the two cavities of the thorax,
and thus lie in perfect contact with the sacs of the
pleura, to which, as well as to the other parts
contained in the thorax, they apply and accom-
modate themselves with the utmost definitude and
exactness.
VOL. I. G § 132. 

98 OF RESPIRATION.
§ 132.
These viscera are appended to an air tube com-
monly called the aspera arteria, which, (besides
an internal membrane, lined with mucus, under
which is expanded a nervous intertexture of ex-
treme sensibility), consists also of a muscular coat,
which surrounds the nervous expansion, and on
the posterior side is easily distinguished at the ter-
minations of certain cartilaginous arches, which
assist in the formation of the tube, but are not uni-
form in their number.
§ 133.
After the aspera arteria has entered the thorax
it first forms, by bifurcation, the two trunks of
the bronchiæ, which as they shoot still deeper and
deeper into the lobes and lobules of the lungs, pass
again, by reiterated divisions and subdivisions, into
branches and ramifications, uniformly decreasing
in size. During these progressive and multiplex
divisions into inferior orders, both the small carti-
laginous rings, and their muscular coat gradually
disappear, till the evanescent extremities of the
tubes finally terminate in those minute cells,
which constitute by far the greater and more im-
portant part of the substance of the lungs, as their
office is to receive, and again discharge the vivify-
ing aerial element, in the process of respiration.
§ 134. 

99 OF RESPIRATION. 
§ 134.
Those small air cells do not appear to possess
uniformly, either the same figure or dimensions.
With respect to the former of these, (viz. their
figure), it is in general that of a polyhedron. The
latter, (i. e. their dimensions), as far as their super-
ficial extent is embraced in the consideration, can-
not without the utmost difficulty, be ascertained;
but, if we consider only their aggregate capacity,
this, in the lungs of an adult subject, whose inspi-
rations are full and strong, is sufficient to admit
and contain about 60 cubic inches of air. We do
not here speak of the immense size, to which the
lungs may be expanded by inflation, after the tho-
rax is opened, but only of the quantity and volume
of air which they do actually admit in the living
subject, when the process of respiration is per-
formed with ease and vigour.
§ 135.
These vesicles or cells, destined for the reception
of air, are every where surrounded and bound
together by that common, but extremely tender,
cellular membrane, which, as we have already
learned, constitutes a general vinculum or bond of
union to the whole body. But it is necessary to
distinguish clearly and accurately between the two
kinds of cells which exist in the pulmonic system.
I have seen the air cells so separate and distinct, 
G2 in

100 OF RESPIRATION.
in the lungs of a healthy human subject, that a per-
son's breath, gently and cautiously blown through
a very minute and tender ramification of the bron-
chiæ, would elevate only a single circumscribed
cluster of vessels or cells, and would neither pass
into the neighbouring cells of the same kind, nor
yet into the common cellular membrane, which is
every where interposed between those cells in- 
tended for the reception of air. But, if the breath
be urged with considerable force, the air cells
will be lacerated, and such a communication form-
ed with the surrounding cellular membrane, as to
give free passage to the subtle elastic fluid, and
thus the whole and every part, of the pulmonary
lobe, will appear to be inflated.
§ 136.
This exceedingly tender cellular membrane,
which encloses and lies between the air vesicles of
the lungs, is every where interspersed with innu-
merable small ramifications of both kinds of pul-
monary vessels, viz. of the pulmonary artery, and
of the four pulmonary veins, the branches of
which accompany the branches of the bronchiæ,
and afterwards, form in their course, by an im-
mense number of divisions and subsequent anasto-
moses, reticular intertextures, and expansions of ex-
treme fineness and subtilty. This truly astonishing
reticular tissue, running in all directions through
the 

101 OF RESPIRATION. 
the cellular membrane, so completely surrounds,
and closely embraces, the cells destined for the
reception of air, that the whole volume of blood,
which passes in an incessant round through the
pulmonic system, is separated from the air taken
in at each inspiration, by nothing else than mem-
branes so amazingly fine and subtle, as scarcely to
be equal in thickness, (according to the observa-
tions and calculations of Hales), to the one thou-
sandth part of an inch.
§ 137.
As we have already observed, that each indivi-
dual ramification of the bronchiæ has appended to
it its own peculiar cluster of air vesicles (§ 135), so
likewise it appears, that to every individual vesicle
of each cluster is peculiarly appropriated its own
system of small blood vessels, the minute rami-
fications of which communicate very frequently
with one another, forming those surprising reticu-
lar tissues aleady spoken of, but scarcely appear to
anastomose, in any degree, with the small blood-
vessels of the adjacent clusters. That this is a
truth we are taught, if I am not deceived, as well
from microscopical observations made on the lungs
of living frogs and serpents, as from more minute
and successful injections of the lungs of human
subjects: the same thing is also further evidenced
by certain pathological phenomena which may be
G3 observed 


102 OF RESPIRATION.
observed in vomicæ, and other similar topical affec-
tions of the pulmonic system.
§ 138.
It is necessary to mention also, in the last place,
that singular and striking apparatus of lymphatic
vessels, which spreads and appears, in a more parti-
cular manner, on the external membrane by which
the lungs are invested. To this apparatus of ves-
sels belongs that numerous assemblage of lympha-
tic or conglobate glands, which, though of a quite
different and distinct order, are nevertheless com-
monly confounded, through mistake, with those
glands in their neighbourhood, which are called
bronchiales.
§ 139.
The thorax, in which the lungs are securely
enclosed, has for its foundation or skeleton, bones
and cartilages, arranged and disposed somewhat
like the walls or sides of a cave. Though this
bony cavity, taken together as an entire whole,
be to a considerable degree firm and steady, yet
most of its parts are so pliant and moveable, as to
be well adapted for the performance of those mo-
tions which the business of respiration requires.
This pliability, or facility of motion is particu-
larly observable in six pairs of the true ribs, which
being 

103 OF RESPIRATION.
being placed beneath the superior and first pair,
are more moveable in proportion as their situation
is lower; or their aptitude for motion is com-
mensurate with the superior length of their bodies,
and cartilaginous appendices, which connect them
to the margins on each side of the sternum, by a
species of articulation called amphiarthrosis.
§ 140.
Between the edges of those ribs lie two strata
of intercostal muscles, the fibres of which assume
indeed and pursue different directions, but which,
nevertheless, co-operate in their action in pro-
ducing the same motion in the parts to which
they are attached.
Across the basis or inferior part of the whole
of this cavity the diaphragm is stretched, somewhat
in the form and direction of an arch. This is a
muscle worthy of particular attention, and, to use
the words of Haller, next in importance to the
heart itself; its parts appear to depend chiefly on
the phrenic nerve for their fitness to co-operate in
the function of respiration, as was long since de-
monstrated by the celebrated live-dissections of the
immortal Galen.
The 

104 OF RESPIRATION.
The diaphragm alternates for the most part, by
an antagonizing motion, with the muscles of the
abdomen, especially with the external and internal
oblique, and the transverse muscles.
§ 141.
The thorax thus formed and finished is, in the
living human subject after birth, alternately dilat-
ed at the time of each inspiration, and contracted
again to its former dimensions in every subsequent
act of expiration.
In inspiration, the enlargement of the tho-
racic cavity extends, in a more especial manner,
laterally and downwards, so that the bodies of
those ribs of which we have particularly spoken
(§ 139) are elevated, and their inferior margins
or edges turned in some degree outwards; while,
at the same time, the arch of the diaphragm is
somewhat depressed, and brought nearer to the
position of a plain, or level surface.
But as to what is boldly asserted of the sternum,
viz. that its inferior end is at the same time pro-
truded forward, this is a phenomenon which I
must confess, I have never been able to observe in
the tranquil and unmolested respiration of a healthy
person.
§ 142.

105 OF RESPIRATION.
§ 142.
This alternate motion of the thorax, which in
a healthy subject is indeed performed spontane-
ously and without effort, is uniformly continued
from the moment of birth to the extinction of life,
for the following necessary and important pur-
poses, namely, that the lungs themselves may, by
a similar vicissitude of motion, be expanded for the
free admission and convenient reception of the air
we inspire, and again contracted in order that the
same may be forthwith expelled.
§ 143.
For man, together with all other warm blooded
animals, is prevented, by absolute necessity, from a
lengthy retention of the air which he inspires; he
is obliged, after a very short period to discharge it
again, and exchange it for a fresh supply of this
vital pabulum or food, as the air has been termed,
even from the most remote ages. It appears in-
deed from the most common observation, that the
air which is inspired and retained any time in the
lungs, however great may have been its original
purity, suffers, in a very short time, such remark-
able changes as affect it with the most obvious
contamination, and, unless it be speedily renewed,
render it wholly unfit to be any farther employed
in the important process of respiration.
§ 144. 

106 OF RESPIRATION.
§ 144.
Enquiries have been instituted for the purpose
of ascertaining the nature of those changes which
the air we inspire undergoes in our lungs. Such
changes certainly do not arise, as was formerly
believed, from the loss of any mysterious principle
of elasticity, which resides in the air, but are evi-
dently produced by a decomposition of its elemen-
tary parts. For the atmospheric air which we
breathe is truly an astonishing mixture of elemen-
tary substances, very widely different from each
other in their natures. Not to mention the va-
rious heterogenous matters which this necessary
fluid contains; such, for example, as the aerial
seeds of the smallest and most simple plants, the
odorous effluvia arising from numerous bodies,
volumes of dust, and a thousand other similar sub-
stances, which for the most part float in the at-
mosphere. Not to mention, I say, these hetero-
genous bodies at all, the air which we breathe
always contains aqueous exhalations in larger or
smaller quantities, and is also more or less charged
with the matters of electricity and magnetism.
But finally, though the whole of the foregoing
substances be left entirely out of view, yet even
then the air of our atmosphere docs not consist of
one simple aeriform fluid, but is composed of de-
phlogisticated, phlogisticated, and fixed airs.
The 

107 OF RESPIRATION.
The proportion of those elementary matters,
especially of such as are organic, is varied ex-
tremely from diversity of places, and by the nature
of the bodies which exist in these places. It is in
the mean time, however, the common estimation,
that the air of our atmosphere consists of about
1/4th part of dephlogisticated, 11/10ths of phlogisti-
cated, and 1/6th of fixed air.
§ 145.
It appears, that at each inspiration, (in which
an adult subject, breathing in a quiet and tranquil
manner, draws in about 30 cubic inches of air,) a
fourth part of the dephlogisticated air is decom-
posed, and, in a great measure, exchanged for
phlogisticated and fixed airs; so that the expired
fluid, being received into a proper vessel, extin-
guishes flame or coals when immersed into it, pre-
cipitates lime from the water which suspends it,
and far exceeds atmospheric air in its specific gra-
vity, &c.
§ 146.
It is probable that the igneous parts of the de-
phlogisticated air, i. e. those parts suited to favour
the process of combustion, being set at liberty by
the decomposition which takes place in the lungs,
enters the arterial blood, and is thus distributed
throughout the whole body; while, on the other
hand, 


108 OF RESPIRATION.
hand, the basis of fixed air is carried back, along
with the phlogisticated and venous blood, to the
right side of the heart, and thence (as the an-
cients were pleased to express themselves) ex-
creted through the lungs like foot.
The more florid dye of the arterial blood, the
more obscure colour of the venous, and the simili-
tude of colours imparted to both kinds of blood,
when exposed to the action of those species of air
now under our consideration (§ 16), are circum-
stances very much in favour of the preceding
opinions.
§ 147.
In a fœtus which has never yet received vital
air into its own pulmonic system, there is in general
less difference between the arterial and venous
blood, than in an adult subject, in whom the pro-
cess of respiration has already taken place.
After the infant is born, the new sensation, ex-
cited by the contact of an unusual element, in an
animal which had hitherto led an aquatic life, and
the application of various other stimuli altogether
new, appear to afford us a happy clue for explain-
ing the new motions which at that period take
place in the body, more especially the dilatation
of the thorax and the first act of inspiration.
When 

109 OF RESPIRATION. 
When the lungs are dilated by this first complete
act of inspiration, a new passage is thus opened
through them for the blood, so that this fluid is
ever after diverted from the umbilical vessels to
the thorax.
But when this inspired air is, by that decompo-
sition of its elementary parts, of which we have
already spoken, rendered both noxious and trou-
blesome to the lungs, I ascribe to the most simple
preservative efforts of nature, the immediately sub-
sequent motion, by which this poisonous mephitis
is exspired, and profitably exchanged for a fresh
supply of the fostering pabulum of life.
From all the foregoing circumstances, taken
collectively, (especially if we attend to the great
influence of respiration on the circulation of the
blood, as demonstrated by the well known experi-
ment of Hooke), we are furnished with a much
better explanation of the celebrated problem of
Harvey, than has yet been given by most of the
other reiterated labours of physiologists, who have
attempted to solve that difficulty.
SECT. 


110 OF VOICE AND SPEECH.
SECT. XII.
OF VOICE AND SPEECH.
§ 148.
THE leading function of respiration
has been already the subject of our consideration.
We will speak, in another place, of the part which
this sublime process acts, in blending and intimately
uniting the chyle with the blood, and also of the
services which it renders, in a variety of ways, to
almost the whole class of natural functions, (§ 63.
112.) We now proceed to consider its other uses
in the animal economy.
The first object or phenomenon which attracts
our attention, in this investigation, is the Voice,
which belongs to the human subject after birth,
and evidently proceeds from the lungs, as was
long since very justly observed by Aristotle, who
said, that no animals are vocal, i. e. possess the
power of emitting sound, but such as breathe
through lungs. For, by the denomination of voice,
we properly designate that sound formed, by means
of the exspired air, in the larynx, which is a small
apparatus or machine of the most exquisite struc-
ture, placed on the top of the wind-pipe or aspera
arteria, 

111 OF VOICE AND SPEECH.
arteria, somewhat like a capital on the summit of
a column.
§ 149.
This small machine is composed of various car-
tilages joined together somewhat after the form of
a capsula or casket. These cartilages are furnished
with a great and truly admirable apparatus of mus-
cles, in consequence of which, not only the whole
are rendered fit for motion collectively, but some
of them are also enabled to move individually and
alone, according to the different variations about
to be produced in the voice.
§ 150.
That part which is more particularly engaged in
the immediate generation of the voice is the glottis,
a very narrow passage leading into the wind-pipe
from above, to which is prefixed, or applied as a
lid, a minute cartilage called the epiglottis. That
found is produced by the air expelled from the
lungs, striking, in a proper direction and with due
force, against the edges of this strait passage, is a
matter too plain to admit of a doubt.
§ 151.
Controversies have existed on the subject of
those changes that take place in the glottis, by
which the modulations of the voice are produced,
namely, 

112 OF VOICE AND SPEECH.
namely, Whether this cartilaginous part be alter-
nately expanded and contracted, as was the opi-
nion of Galen, and afterwards of Dodart? or,
Whether the variations of the voice do not rather
depend on the tension and relaxation of its liga-
ments, as was held by Ferrein?
The latter of those, therefore, compared the
primary organ of the voice to a violin, the former
to a flute—i. e. the one set of disputants conceived
it to emit found on the principles of a corded, the
other on those of a wind, instrument of music.
From a faithful collection, and impartial consi-
deration, of all the arguments which have been
advanced on this contested point, we are of opi-
nion, that both kinds of changes do actually take
place in the glottis when employed in the emission
of found; but we, nevertheless, believe, that the
principal and most important of those changes de-
pend on and arise from the tension of the liga-
ments, more especially of the thyreo-arytonoidei
inferiores (which appear to have been the vocal
cords of Ferrein.
§ 152.
That all this mobility of the glottis, of whatever
kind it may be, is influenced and wholly directed
by the numerous muscles which belong, and are
attached, 

113 OF VOICE AND SPEECH. 
attached, to the larynx, may be fully established
by the following beautiful experiment, viz. If the
recurrent or wandering nerves (as they are termed)
be either secured in light ligatures, or completely
cut asunder, the voice of the animals subjected to
such experiments, will be in the former case, ren-
dered extremely weak and low, and in the latter,
entirely destroyed.
§ 153.
The faculty of whistling belongs in common
both to the human species, and to small birds of
note. To qualify them for this, singing birds are
furnished with a bifurcated larynx at each extre-
mity of the aspera arteria. But though human
subjects be supplied with only one plain and simple
larynx, yet they learn to imitate those small ani-
mals, as appears to me, by a co-arction or pucker-
ing up of their lips.
§ 154.
But song, which is composed of speech and a
harmonious modulation of the voice, I would con-
sider as peculiar to man alone, and as constituting
the leading prerogative of his vocal organs. The
faculty of whistling is, as already observed, a part
of the birth-right of birds: a numerous train of
the feathered race, and sometimes even dogs them-
selves, have also been taught to pronounce a va-
VOL. I. H riety 

114 OF VOICE AND SPEECH.
riety of words. But I doubt extremely indeed,
whether any brute animals have ever yet possessed
a faculty of true and genuine song; whereas, on
the other hand, I believe there scarcely exists a
a nation so barbarous, where song does not very
generally prevail.
§ 155.
Speech itself is a peculiar modification of the
voice, chiefly by the aid of the tongue, but par-
tially also by that of the lips, the teeth, the palate,
and by the further assistance of the nose, combined
into the formation of words.
Hence the difference between voice and speech
appears very obvious and plain: the first is evi-
dently formed in the larynx itself; whereas the
latter is effected by the singular mechanism of the
other organs already mentioned. It is but just
and proper, however, to observe, that this last
position is not capable of universal application, as
there are a few nations (of which the Sinensians
may serve as an example), among whom their al-
most homonymous* words are distinguished only
by a varied modulation of the voice itself.
* A word is said to be homonymous, when it is highly
equivocal, or used indiscriminately to represent a discordant
variety of objects or things.
But 


115 OF VOICE AND SPEECH. 
But further, voice belongs in common to brutes
as well as to man; it is possessed also by the new-
born babe, nor is it wholly denied to such unhap-
py infants as have passed their lives amidst the
haunts, and in the gloomy society, of wild beasts,
nor even to those that have been born without the
sense of hearing. But speech is not acquired till
after the cultivation and exercise of reason; it
constitutes, therefore, no less than that operation
of the mind itself, a characteristic privilege, and
distinctive prerogative between man and the rest
of the animal kingdom. To serve all the pur-
poses, and answer all the demands of brutes, that
instinct with which nature has beneficently supplied
them, is completely adequate; of this instinct,
however, man is destitute, as also of such other
aids and individual powers as might enable him to
preserve and sustain life by his own solitary exer-
tions; he is therefore kindly furnished with the
prerogatives of reason and speech, by means of
which, embracing the advantages, and discharg-
ing the duties, annexed to a social state, he is able
both to disclose his own wants, and relieve those
of his fellow creatures.
§ 156.
That truly admirable mechanism, by means of
which speech and the pronunciation of letters are
H2 effected, 

116 OF VOICE AND SPEECH.
effected, has, since the celebrated researches of
that paradoxical character, Franc. Mercur. Hel-
mont, been very much illustrated and explained
by further and later enquiries, especially those of
Jo. Wallis and Conr. Ammanus.
That division of the letters by Ammanus into
I. Vowels, II. Semivowels, and III. Consonants,
is, of all others, by far the most simple and na-
tural.
I. Vowels he again divides into simple, as a, e, i,
y, o, u, and mixed, as, ä, ö, ü.
II. Semivowels are themselves either nasals,
such as m, n, ng, (i. e. n placed before g in the
German language); or Orals (otherwise called
Linguals) such as, r, l.
III. Finally, Consonants he divides, 1st, into the
Sibilantes or hissing (i. e. into those consonants the
pronunciation of which can be continued for an
indefinite length of time). These are h, g, ch, s,
sch, s, v, ph.
2dly, Explosive, as, k, q, d, t, b, p, and
3dly, Double (or Compound), such as, x, z.
§ 157. 

117 OF VOICE AND SPEECH. 
§ 157.
Finally, It yet remains to mention certain other
modifications of the human voice, which usually
occur as symptoms, or signs of either particular
passions of the mind, or more violent affections of
the organs of respiration. The greater part of
these modifications of the voice, such for example,
as laughing and crying, appear to belong exclu-
sively to the human race.
§ 158.
Most of the modifications which immediately
follow, are connected together by such a powerful
kindred alliance, that one of them is not unfre-
quently observed to pass into another. It must be
also further observed, that the greater part of
them do not always assume and exhibit the same
uniform appearance, &c.
To speak, however, in general terms, in the
act of laughing, exspirations short, interrupted, and
in some measure broken, follow each other in
quick succession.
Crying produces deep inspirations, which sud-
denly alternate with lengthy exspirations fre-
quently interrupted and broken.
H3 Sighing 

118 OF VOICE AND SPEECH.
Sighing consists in a lengthy, full, and strong in-
spiration, and a subsequent flow exspiration, which
is not unfrequently accompanied with somewhat
of a groan.
Coughing is produced by quick and sonorous
exspirations succeeding a deep inspiration.
Sneezing is a more violent and somewhat con-
vulsive exspiration, which had been preceeded by
a short and forcible inspiration.
The Hickup on the other hand consists entirely
of a single inspiration, sonorous, extremely sudden,
and at the same time of a convulsive nature.
The present seems a very suitable occasion to
speak of the phenomenon of yawning, which con-
sists in a full, slow, and lengthy inspiration, suc-
ceeded again by a similar exspiration, while, at
the same time, the jaws are drawn so very widely
asunder, that the air which is received into the
expanded fauces can enter with ease the Eusta-
chean tubes. One thing peculiar to this pheno-
menon is, its being extremely contagious, i. e. it
very readily excites to imitation: the cause of this
is, without doubt, to be sought for in the remem-
brance of the agreeable sensatious produced at a
former time, by the languid operation of yawning.
SECT. 

119 OF ANIMAL HEAT. 
SECT. XIII.
OF ANIMAL HEAT.
§ 159.
IT is worthy of observation, that man in
a living state, together with the other subjects be-
longing to the class Mammalia, as well as the whole
feathered race, are distinguished from the rest of
the animal kingdom by this peculiarity, that the
native heat of their bodies far exceeds, in degrees
of temperature, the usual heat of the medium or
element in which they live. With respect to man
himself, it is however to be remembered, that he
appears to be inferior, in the heat of his system,
to those other kinds of animals we have just men-
tioned. Thus, in our climate, the heat of the
human body generally stands at about the 96th
degree of Fahrenheit's scale, whereas, in other
animals belonging to the class Mammalia, the vital
temperature very considerably exceeds this point,
while it ascends still higher in individuals of the
feathered tribes.
§ 160.
Indeed, the degree of native heat possessed by a
healthy person is so constant and uniform, that in
H4 general, 


120 OF ANIMAL HEAT.
general, (provided we make allowance for the
state of health peculiar to each individual), its
range will include but a very few degrees of the
thermometer, whether the subject be exposed to
the inclemencies of the most rigorous climate, or
placed beneath the fervors of a tropical sky. For
the opinion formerly delivered by Boerhaave, that
man has not a power of existing in a medium of
such a nature as exceeds in temperature the native
heat of his own body, has, since the famous ob-
servations of that illustrious traveller and former
governor of Georgia, H. Ellis, been refuted by a
great number of characters learned in the science
of physiology, and the reverse completely demon-
strated and established by experiments well adapted
to the nature of the subject. In this particular,
indeed, appears to consist one of the great prero-
gatives of man, that imprisoned and confined to
no one climate or zone of the earth, he is able to
pass his life in any section of the immense globe
we inhabit, and is free to fix his habitation either
beneath the rigors of Hudson's stormy channel,
where the quicksilver passes spontaneously to a
state of complete congelation, amidst the tempests
of Nova Zembla, or in the bosom of those glaring
solar fires, which scorch the glowing shores of the
Senegal.
§ 161. 
 

121 OF ANIMAL HEAT. 
§ 161.
We proceed now to enquire into the origin and
source of that astonishing fire, which minutely
pervades our bodies, and uniformly supplies them
with their necessary degrees of warmth. To pass
in silence over the visionary conjectures of the
ancients on this subject, some of the moderns have
attempted to derive animal heat, with all its phe-
nomena, from the matter of electricity and the
nerves, others from the attrition generated by the
circulation of the blood, others from the recipro-
cal friction between the solid elementary parts of
living animals, while others, again, have embraced
and defended different opinions.
§ 162.
But all those hypotheses are embarrassed with
insurmountable difficulties, whereas, on the other
hand, the utmost simplicity, and an entire cor-
respondence to the phenomena of nature, combine
in recommending and confirming that doctrine, in
which the lungs are considered as the focus or fire-
place where animal heat is generated, and the de-
phlogisticated part of the air which we breathe,
as the fuel that supports the vital flame. That
justly celebrated character, Jo. Mayow, sketched
out, formerly, the leading traces and first great
outlines of this doctrine, which, in our times, has
been greatly improved, extended, and farther
elucidated,

122 OF ANIMAL HEAT.
elucidated, by the labours of the illustrious Craw-
ford.
§ 163.
The whole drift and tenor of Crawford's theory
obviously results in this, that respiration, no less
than combustion, belongs to such processes as are
called phlogistic; in which the phlogiston residing
in, and constituting a part of, our bodies, is ex-
pelled by the accession of free or sensible heat,
(which ought to be carefully distinguished from
heat existing in a fixed or latent state.)
For phlogiston and the matter of heat are ele-
ments of such contrary and opposite natures, that
the greater quantity of the one our bodies at any
time contain, the less, at the same time, is their
proportion of the other; thus, fixed air, for ex-
ample, is not supposed to contain more than 1/67th
part of the quantity of the matter of heat, which
belongs to an equal weight of atmospheric air, &c.
But it appears, from experiments, that atmo-
spheric air has a stronger affinity to phlogiston
than to the matter of heat, so that it unites itself
with the greatest readiness to the former, while, at
the same time, it sets at liberty the latter, which
had been hitherto held in a fixed and latent state.
§ 164.

123 OF ANIMAL HEAT. 
§ 164.
When we come to apply the foregoing posi-
tions and principles to the phenomena of respira-
tion, it appears highly probable, that animal heat
is generated by a process of a similar nature.
For, as we have already had occasion to ob-
serve, the air which we exspire differs, in a very
remarkable degree, from what we had immediately
before inspired; being deprived of its igneous
portion, or of that part fit for contributing to the
support of flame, it is returned highly impreg-
nated, on the contrary, with phlogiston and the
base of fixed air. (§ 146.)
§ 165.
It appears, therefore, extremely probable, that
the igneous portion of the air we breathe enters
those minute blood-vessels, which are every where
dispersed throughout the substance of the lungs,
and separated from the air-vesicles themselves by
nothing more than subtle partitions of the most
filmy texture (§ 136); that from the lungs it is
conveyed through the pulmonary veins to the
aorta, from whence it is again, by means of the
arterial system, distributed throughout every part
of the body.
During 


124 OF ANIMAL HEAT.
During the whole course of this minute distri-
bution, more especially while in the extreme ra-
mifications of the vessels, it appears to be ex-
changed for phlogiston, which it every where
meets with in considerable quantities. This phlo-
gistic principle, being thus mixed with the blood,
and occupying the place just evacuated by the
matter of heat, is conveyed back, by means of the
venous system to the right side of the heart, and
from thence by the pulmonary artery, into the
lungs, where, agreeably to those laws of affinity
which we just now hinted at, it is immediately
received and taken up by the volume of air
recently inspired. In consequence of the accession
of this quantity of phlogiston, and its union with
the air contained in the lungs, a fresh portion of
the element of fire or heat is set at liberty, which
instantly enters the blood and is thus incessantly
distributed throughout the system in the manner
already described.
§ 166.
The truth of this theory is evidenced by those
diversities between arterial and venous blood, to
which we have every where adverted. It is
also farther evidenced by the difference between
the specific heat of arterial, and that of venous
blood; thus the specific heat of the blood con-
tained in the arteries is to that of the blood con-
tained 

125 OF ANIMAL HEAT. 
tained in the veins, as 11 1/2 to 10. Finally, as an
additional evidence of the same thing, we might
mention, in the last place, that oscillatory action
exerted by the smallest order of blood vessels,
which was the subject of our attention on a
former occasion.
§ l67.
For it seems altogether probable, that those
extremely minute ramifications of the sanguiferous
system, are parts of such utility and importance,
that in proportion as their action is stronger or
weaker, a correspondent increase or diminution
takes place in that exchange of the element of fire
for the matter of phlogiston, which goes constantly
forward in the body, and also in the heat of the
animal uniformly generated by such exchange.
Those memorable and striking phenomena, from
which it appears, that animal heat (if indeed the
matter be determined by a thermometer, and not
trusted to the fallacious test of sensation), remains
in general at very nearly the same precise point of
temperature, little augmented by the summer's
blaze, little diminished by the winter's blast; and
further, that on certain occasions the heat of our
bodies is even increased in consequence of an im-
mersion in cold water—Those phenomena, I say,
seem to demonstrate, and reduce it to a certainty,
that 


126 OF PERSPIRATION.
that according to the variations that take place in
the temperature of the medium in which we live,
corresponding diversities immediately follow in the
action of the smallest vascular ramifications of our
bodies. From this singularly accommodating
power, resident in the minute extremities of our
vascular system, it follows, that on being exposed
to cold (which appears to act by increasing their
tone), they are immediately enabled to exchange
a larger quantity of the principle of phlogiston for
the igneous pabulum, and thus generate a higher
degree of heat; whereas, on the other hand,
they are obliged to exchange a much smaller quan-
tity, as often as they are rendered inactive by be-
ing subjected to the influence of a relaxing and
debilitating medium.
SECT. XIV.
OF CUTANEOUS PERSPIRATION.
§ 168.
So various, and extremely diversified,
are the functions of the cutis, with which the hu-
man body is invested, that an enumeration and
complete account of the whole of them can
scarcely be comprehended with propriety under
one 
 

127 OF PERSPIRATION. 
one and the same head; they would appear to
be more fitly arranged for consideration, each one
under that class of actions to which, from its
nature it belongs.
For, in the first place, the cutis is the organ of
touch, of which we will speak when treating of
the animal functions.
It is again the medium or instrument of inhala-
tion, by which office it makes a part of the
absorbing system of lymphatics; this shall be a
subject of further consideration, when we come
to take a view of the natural functions.
Finally, It is the laboratory or organ of perspi-
ration also. This function agrees in a great
variety of respects with the process of respiration,
and appears therefore to be introduced with
sufficient propriety as the subject of the present
section.
§ 169.
The cutis is said to consist of a threefold mem-
brane, or of a membrane composed of three
laminæ. These laminæ or layers are the corium
or true skin, lying on the interior side, the cuticula
or cuticle making the exterior covering, and the
reticulum (i. e. the rete mucosum), which is spread
between 


128 OF ANIMAL HEAT.
between the two laminæ just mentioned. Of each
of these we will treat severally and in order.
§ 170.
The cuticle, or epidermis, forms, as just ob-
served, the external covering to the whole body:
It is thus, from its situation, exposed to a free ac-
cession of the air, the immediate contact of which
element, scarcely any other part of the body can
bear with impunity, even in a sound state, except
the enamel of the teeth, the tubes of respiration,
and the alimentary canal.
§ 171.
The texture of the epidermis is simple to the
utmost degree, being entirely destitute of vessels,
of nerves and of pores. This texture, though on
the whole scarcely organic, is nevertheless highly
singular and striking; notwithstanding its semipel-
lucid and tender appearance, its tenacity is yet so
very considerable as to resist effectually, for a
great length of time, not only maceration, but
various other modes of generating putrefaction.
§ 172.
The origin of this filmy expansion is as yet in-
volved in doubts and difficulties. It is in the
mean time, however, probable that it springs,
along with the small bulbs surrounding the roots
4 of 

129 OF PERSPIRATION.
of the hairs, from the corium or true skin expanded
beneath it: that this is the case, we are led to in-
fer, from the myriads of minute and extremely
tender fibrils, by which it and the skin are con-
nected together.
When by any means destroyed, it is re-pro-
duced again with greater facility, than any of the
other solid parts of the human body.
§ 173.
That this membranous lamina is of the utmost
importance in the economy of organized bodies,
is incontestibly evinced by its universal prevalence
throughout both the animal and vegetable king-
doms. It may be observed already formed even
in the tender embryo itself, at so early a period as
the third month after the time of conception.
§ 174.
Underneath the cuticle is expanded a thin mu-
cous membrane, which, from an opinion entertained
respecting it, by its celebrated discoverer, is called
reticulum Malpighianum.
This reticulum or subtle net-like expansion, ex-
hibits the habit and appearance of mucus, ex-
tremely easy of solution: it can scarcely in any
part, except in the scrotum of Æthiopians, be sepa-
VOL. I. I rated 

130 OF PERSPIRATION.
rated entire from both the cuticle and true skin,
and thus be procured in the form of a genuine and
complete membrane.
§ 175.
The part now under consideration, constitutes
the primary and principal feat of colour in the
human race. In all men the true skin is fair and
shining; the cuticle also is semipellucid and whitish
in all nations, except the inhabitants of Æthiopia,
in whom it is more duskish and obscure. But in
the human subject after birth, the colour of the
reticulum mucosum is varied, in correspondence to
the diversities of age, mode of life, climate, and
also in proportion as the constitution is more or
less found.
Thus, for example, of the five varieties, into
which the human race appears to me, to be with
much propriety divided, the first has the reticu-
lum more or less whitish. This description in-
cludes, besides Europeans, those who inhabit the
west of Asia, and the north of Africa, together
with the natives of Greenland and Esquimaux.
2dly, In the second variety, which includes the
inhabitants of all the other parts of Asia, the reti-
culum somewhat tawny, inclining to an olive
cast.
3dly, 

131 OF PERSPIRATION. 
3dly, In the third, which embraces the inhabi-
tants of Æthiopia, it is blackish.
4thly, In the fourth, which consists of the ab-
origines of America, it is to a certain degree cop-
per-coloured.
5thly, Finally, in the fifth, which comprehends
the inhabitants of all the South Sea islands, it is
more or less tawny or brown.
But all, and each one of those varieties of co-
lour, as well as all other varieties, by which man
differs from man, and nation from nation, appear
to be so intimately blended together, and are dis-
posed to run into each other with so much facility,
that it seems scarcely possible to establish any divi-
sions or classes of them, but such as are plainly
arbitrary.
§ 176. 
The Corium or true skin itself, to which the
reticulum and epidermis serve as a covering, is a
membrane of a peculiar nature; it is porous, te-
nacious, capable of vast dilatation, varied in its de-
grees of thickness, consisting chiefly of condensed
cellular membrane, and extremely close and com-
pact on its external superficies; it is more lax on
the internal surface, which, (if you except a few
I2 regions 

132 OF PERSPIRATION.
regions or parts of the body)(§ 36.) contains, for
the most part, a certain quantity of common fat.
§ 177.
Besides nerves and absorbents, of which we will
speak particularly on a future occasion, the corium
or true skin is also plentifully supplied with innu-
merable small blood-vessels, which run on its exte-
rior surface, and, as we learn from a successful
injection, invest the same with reticular expansions
of the most close and subtile texture.
§ 178.
Over the same exterior surface is also inter-
spersed an immense assemblage of small sebaceous
follicles, which thoroughly anoint the whole cutis
with a very subtle and limpid oil, of such a nature
as not to be easily evaporated and dried up. This
fine fluid should neither be confounded with the
common sweat, nor yet with that fetid substance
which infests only some particular parts of the
body.
§ l79.
Finally, almost the whole of the true skin is
planted with hairs of various kinds. The most
numerous and abundant of these are very short
and tender, inclining more or less to the nature of
down; of hairs which fall under this description,
scarcely

133 OF PERSPIRATION. 
scarcely any part of the body is destitute, except
the eye-lids, the male penis, the palms of the
hands, and the soles of the feet. But, on certain
parts of the body, the hairs, being destined for
particular uses, grow to much greater lengths;
examples of this we have in the hair of the head,
in the eye-brows, in the eye-lashes, the hairs in
the nostrils, the whiskers, the beard, together with
such hairs as grow in the arm-pits, and about the
anus and parts of generation.
§ 180.
In general, man is indeed less hairy than most
other animals belonging to the class mammalia,
A difference exists, however, in this respect, be-
tween the inhabitants of different countries. For,
to pass in silence over those nations who are in
the daily practice of plucking out, as well the
beard, as the hairs which appear on other parts
of the body, there are not wanting certain tribes,
who are naturally destitute of hair; of this descrip-
tion appear to be the Tungusæ and the Buratæ.
On the other hand, we are informed by travellers
of the highest reputation in point of veracity, that
the inhabitants of Nadigsda, one of the northern
Kurilikian islands, are remarkable for the unusual
quantities of hair with which their bodies are pro-
tected,
I3 § 181.
 

134 OF PERSPIRATION.
§ 181.
Neither are the varieties fewer, which are ex-
hibited by the hair, in regard to length, flexility,
curliness, and, more especially, in point of colour:
this last property depends, in general, on the power
of climate, on age, and other causes, which exert
their influence in perfect conformity to the esta-
blished laws of nature; but it sometimes also de-
pends on a morbid and misplaced temperament, as
appears to be the case in the white natives of
Æthiopia. The colour of the hair corresponds,
for the most part, to that of the eyes.
§ 182.
There is also a further peculiarity in the direct-
tion of the hairs, on certain parts of the body;
thus, for example, on the vertex or crown of the
head, they pursue a spiral direction; on the pubes,
they diverge and point upwards; on the posterior
side of the arm, they look, (as on the ape, and
contrary to their direction on the satyr), towards
the elbow, (that is, they point from the shoulder
downwards, and from the wrist upwards): of the
directions pursued by the eye-brows and eye-lashes,
it seems unnecessary to say any thing on the pre-
sent occasion.
§ 183.

135 OF PERSPIRATION.
§ 183.
The hairs originate from the interior surface of
the true skin, which contains a quantity of fat:
they are fixed with considerable firmness in each
of the small bulbs, which are composed of two in-
volucra; the external involucrum is vascular, and
oval; the internal is cylindrical, appears continu-
ous with the epidermis, and serves as an immedi-
ate covering to those elastic filaments of which
each individual hair is itself composed, and which
are from five to ten in number.
§ 184.
The hairs are always completely besmeared with
an oily halitus, and are almost incorruptible. They
appear to possess more of the nature of original
electrics (or of electra per se, as they are called),
than any of the other parts of the body. Their
nutrition is extremely simple and easy, as is also
their re-production after having fallen off, unless
the cutis itself be labouring under some morbid
affection.
§ 185.
Besides other important purposes which these
common integuments of the body serve, they are,
in a particular manner, to be reckoned among the
number of the excretory organs of the system; by
I4 their 

136 OF PERSPIRATION.
their assistance, in this point of view, certain foreign
matters, which would from retention prove highly
noxious, are hourly eliminated and totally removed
from the general volume of our fluids.
The truth of the above position is fully demon-
strated and established, by the well-known circum-
stance of miasmata being completely removed from
the system, under the appearance of exanthemata
or eruptions; it is also proved by the odours of
garlic, musk, and other substances taken into the
body, passing by the skin; it is still further demon-
strated and confirmed by the process of sweating,
and by other phenomena of a similar nature.
§ 186.
But above all, those excretory passages convey
off a certain fluid, which is called the perspirable
matter of Sanctorius, in honour of that most acute
and ingenious philosopher, who instituted the first
series of rational inquiries for the express purpose
of ascertaining its utility and importance.
It is necessary, however, to observe, that under
this appellation, physiologists commonly designate
excrementitious matters, which, if not opposite, are
at least exceedingly different, in their natures, and
which ought, therefore, to be distinguished from
each other with the utmost accuracy and care; as
the

137 OF PERSPIRATION. 
the excretion of sweat, for instance, from the
genuine matter of perspiration.
The former (i. e. the sweaty excretion) is a
liquid of an aqueous nature, saltish to the taste,
and which scarcely ever issues spontaneously from
the healthy body when in a state of tranquility
and rest.
But the latter, (viz. the genuine matter of per-
spiration), of which alone we intend to treat on
the present occasion, is an aeriform fluid, perman-
ently elastic, and bearing a very striking resem-
blance to that which we exspire by the lungs.
§ 187.
Like that elastic fluid, it is highly charged with
the principle of phlogiston, like that, it precipitates
quick-lime from the water in which it was sus-
pended, and, like that, it is also unfit both for
contributing to the nourishment of flame, and also
for supporting the process of respiration, &c.
§ 188.
The quantity of this fluid that exhales from the
whole superficies of the body (which, in an adult
human subject of the middle size, amounts by
measurement to about fifteen square feet) can
scarcely be reduced to accurate calculation.
For, 

138 OF PERSPIRATION.
For, that the scales, which from the time of
Sanctorius have been made use of for ascertain-
ing the exact weight of the body, are not well cal-
culated for determining the precise quantity of this
elastic fluid, may be easily understood from what
we have just now said respecting the different sub-
stances which are eliminated from the system by
the skin, besides the true matter of perspiration.
It was long since discovered, that the nature
and quantity of perspiration vary extremely, not
only in different persons, but even in the same
persons, at different times. It seems at present,
however, to be a point too well ascertained to
admit of a doubt, that there does really exist,
with respect to the matter perspired, a national
variety and peculiarity; the truth of this we con-
fidently rest on what has been said, by authors of
the highest veracity, with regard to the singular
and specific odours which are transpired through
the skins of the Caribeans, of the Greenlanders,
of the Æthiopians, and also of the individuals be-
longing to other barbarous tribes.
§ 189.
On considering what has been said with respect
to the vascularity observable in the texture of the
skin (§ 177), and also with respect to the analogy
that exists between the matter of perspiration and 
the
 

139 OF PERSPIRATION. 
the air we expire (§ 187); and further, on consider-
ing what has been advanced respecting the power
and influence of the smallest vascular ramifications,
in the generation of animal heat—to him, I say,
who carefully weighs and attentively considers all
these circumstances, it will appear extremely pro-
bable, that there exists a striking similitude indeed
between the action of the lungs in respiration, and
that of the skin in the process of perspiration. It
will appear that there exists between the cutis
and lungs a reciprocal consent; so that the one
may be supposed capable of assisting and some-
what relieving the other, and even of supplying
its place, at least to a certain degree, in case of
any accident or derangement.
§ 190.
In support of this opinion we can adduce the
concurrent testimonies of a variety of phenomena,
observable not only in a sound, but also in a
diseased, state of the system.
Some of these phenomena are, for example,
those leading points, in which the human fœtus,
as well as that of the other animals belonging to
the class mammalia, differ from the incubated
chick, or the young of the feathered tribes, while
yet enclosed in the parietes of the egg.
A further 


140 OF PERSPIRATION.
A further evidence in favour of the same
opinion, is that singular coldness of certain parts
of the body, even in warm blooded animals, (as
in the noses of dogs, &c.) which appears to be
referred with sufficient propriety, to a less phlo-
gistic action of the small vessels, with which those 
parts abound. 
On the contrary, from an encreased action of
the minute vessels in certain parts of the body, we
explain, with the utmost fairness and facility, a
variety of morbid symptoms, such, for instance, as
that singular heat and flushing in the palms of the 
hands, which occur so frequently, and are so 
strikingly observable in patients labouring under
a hectic fever.
With regard to that vicarious action of which
we formerly spoke, and by which we said it ap- 
peared probable, that the functions of the lungs
and cutis lend mutual aid and assistance to each 
other; that such an action does unequivocally
exist, we derive some force of testimony from those
phenomena in pathology, where human subjects, 
after birth, and even after advancing to an adult 
age, having their lungs almost totally destroyed by
a consumption, or highly vitiated by some other
contamination, have nevertheless survived such
melancholy misfortune, for a long time, and in
some 

141 OF PERSPIRATION. 
some cases have even passed several years, during
the whole of which period they appeared to be
almost entirely deprived of the use and advantages
of respiration.
Finally, It does not appear improbable, but
that the interior surface of the alimentary canal,
may also, besides its other primary functions, be
perpetually engaged in the performance of a phlo-
gistic process, not unlike that conducted by the
skin and pulmonary system.
This canal or tube appears, indeed, to be the
only interior part of the body, except the lungs
themselves, to which the atmospheric air has free
access; but that the air has really free access to
the primæ viæ, or first passages, as they are called,
and that we swallow that elastic fluid in con-
siderable quantities, are matters, much too plain,
to stand in need of any proof.
Further, That the air which we swallow
undergoes a change very similar to the change
suffered by that taken by inspiration into the
lungs, is satisfactorily demonstrated by the nature
of the air contained in the whole alimentary canal.
Finally, 

142 OF THE SENSORIUM
Finally, To all those concurring circumstances
we may further add, that truly astonishing con-
geries of small blood vessels, spread in profusion
over the interior surface of the intestines, which
is commonly believed to be equal in extent to the
external superficies of the whole body.
SECT. XV.
OF THE SENSORIUM AND NERVES.
§ 192.
WE come now to treat of another
class of the functions of the human body, which
embraces what we denominated the animal func-
tions (§ 63): by means of these, an uninterrupted
commerce and intercourse are kept up between
the body and the various faculties of the mind.
They belong therefore exclusively, (as indeed the
name itself plainly imports,) to organised and ani-
mated bodies; but as they pervade the whole
animal kingdom more universally than the vital
functions, they appear to have an exceedingly just
and well founded claim to the epithet, animal.
§ 193.

143 AND NERVES.
§ 193.
The organs which are principally subservient to
the exercise of these functions are, the cerebrum,
the cerebellum, and their appendage the medulla
spinalis, together with the nerves that originate
from these three sources. The whole of these
organs may, with sufficient propriety, be ar-
ranged under two leading classes, namely, the Sen-
sorium and Nerves. The former of these em-
braces (if we except the nerves themselves, and
those parts which constitute their more immediate
origins) all the remainder of that whole system,
which forms, more particularly, the vinculum or
medium of connection, that exists between the
offices or functions of the nerves and our nobler
part, the faculties of the mind.
§ 194.
On this division is founded that beautiful obser-
vation of the illustrious Sommering, in which he
alledges, that the relative magnitude which the
two preceding classes of organs bear to one
another, corresponds so accurately with the fa-
culties of the mind, that the smaller and less bulky
the nerves of animals are, when compared to the
size of the other organs or parts which we have
comprehended under the denomination of Sen-
sorium, the more vigorous and active are the fa-
culties or their minds. In this respect he observes,
that

144 OF THE SENSORIUM
that man may be said to possess the largest cere-
brum or brain, if its bulk be compared to the
small size of the nerves that originate and proceed
from it, but not if its weight be compared with
the relative weight of the whole body.
§ 195.
Besides the bony cranium or skull, in which the
cerebrum itself is enclosed, it is still farther invested
with three involucra or coverings; these are the
dura and pia matres, between which is expanded
the third, viz. the tunica arachnoidea.
§ 196.
The dura mater, which lines, as a periosteum,
the cavity of the encephalon, is lengthened out
into a variety of partitions or processes. By its
falciform process, which is the most prominent and
remarkable, it separates from each other, the two
hemispheres of the brain; while, by means of that
process called the tentorium, it forms a partition
between the cerebellum and the parts situated above 
it, and thus, by giving support to the posterior
lobes of the brain, prevents them from making an
undue pressure on the subjacent cerebellum.
Further, the dura mater, by various duplicatures
or doublings of its own membrane, forms what
are called the venous sinuses, while it gives them at
4 the 


145 AND NERVES.
the same time firmness and support, and prevents
them from being unduly compressed. Through
these sinuses the blood of the encephalon, or parts
contained within the cranium, glides back towards
the heart: this blood is said, by physiologists, to
possess properties peculiar to itself, and appears,
from actual calculation, to be so considerable in
quantity as to amount, at least, to one tenth part
of the whole mass of blood contained in the human
body.
§ 197.
Next to the dura mater lies the tunica arachnoi-
dea, so called from its extreme tenderness and filmy
texture. It is destitute of blood-vessels, (§ 5.),
and does not, any more than the dura mater, enter
the various sulci or furrows, and receive the dif-
ferent eminences or ridges, which mark the sur-
face of the cerebrum, but only expands, with uni-
formity, over the whole volume of that important
viscus.
§ 198.
Very different from this is the state and situa-
tion of the internal involucrum or covering of the
brain, on which the ancients bestowed the name
of pia mater. This membrane every where ac-
companies the cortical part of the cerebrum so
closely, that the innumerable small blood-vessels,
VOL. I K with

145 OF THE SENSORIUM
with which it is profusely supplied, enter, and
even perforate the cortex itself, with their infini-
tude of minute ramifications; hence, when the pia
mater is separated by force from the cerebrum, its
external surface presents a smooth and exquisitely
beautiful polish, while its internal surface, on the
contrary, is considerably villous, and resembles, not
a little, those delicate radicles by which the mosses 
adhere to their native soil, or places of growth.
§ 199. 
Both the cerebrum and cerebellum are compos- 
ed of a variety of parts, different from each other
both in texture and figure, the uses of which have 
been hitherto generally unknown: these parts are
particularly distinguished by the four ventricles, as
they are called, the communication between which
has been of late traced and developed, with the
utmost accuracy, by the illustrious Monro: of
these ventricles, the two anterior and the fourth 
contain what are denominated the plexus choroidei,
the uses and functions of which are also involved, 
as yet, in intricacy and doubt.
§ 200.
In all parts, of both the cerebrum and cerebel-
lum, there exist two kinds of substance, one of a
cineritious or ash-colour, which is called the corti- 
cal part, although it does not always form the
exterior 

147 AND NERVES.
exterior stratum, the other white and shining, and
therefore called the medullary portion. Agree-
ably to the observations of the illustrious Som-
mering, there is interposed between the two fore-
going substances, still a third, of a colour border-
ing on white; this body is most conspicuously ob-
servable in the arbor vitæ of the cerebellum, and
in the posterior lobes of the cerebrum.
§ 201.
The proportion, which the cineritious substance
bears to the medullary, decreases as life advances;
thus, in infants it is greater, in adults less. Almost
the whole of this cineritious substance, is com-
posed of an immense assemblage and contexture of
the smallest sized blood-vessels, together with vessels
of an order still inferior, even so minute as to be
incapable of admitting any thing except a white
or colourless fluid of the most exquisite tenuity,
(§ 79.): a small number of these vessels passes
into the medullary portion, which appears to con-
tain in its own composition, (besides these minute
vessels and a quantity of very tender cellular mem-
brane), a soft pultaceous parenchyma, in which
physiologists, even when armed and aided by the
most powerful glasses, have not yet been able to
discover any uniform and definite texture.
K2 § 202. 


148 OF THE SENSORIUM
§ 202.
In the cerebrum is observable a perpetual but
very gentle motion, bearing such a relation and
exact correspondence to the process of respiration,
that while the lungs are collapsed, and their
volume diminished in the act of exspiration, the
cerebrum is slightly elevated, but immediately
subsides again, when the thorax is dilated by
means of a subsequent act of inspiration.
§ 203.
What has been called by physiologists the me-
dulla oblongata, terminates in the medulla spinalis,
which is contained in that flexible tube, formed
by the vertebræ of the spine or back, and is still
clothed in the same membranes which we have
already seen investing the cerebrum or brain itself:
further, as the brain, so likewise the spinal marrow,
is found to consist of two kinds of substance, with
this striking circumstantial difference, however,
that, in the latter, the cineritious or ash-coloured
substance forms the internal, whilst the shining or
medullary composes the external, part.
§ 204.
From each of the foregoing sources, namely,
the cerebrum and cerebellum, together with the
medulla spinalis, the nerves primarily derive their
origins. These are small ropes or cords, of a
colour 

149 AND NERVES. 
colour more or less whitish, differing likewise in
their degree of firmness), which are minutely
distributed throughout almost all the other soft
parts of the human body. This opinion of the
minute, and universal, distribution of the nerves
through every part of the human system, though
admissible as a general rule, is, however, subject
to certain well founded exceptions.
§ 204.
For it appears from an infinitude of experiments
made by the illustrious Haller, and other able
observers, that there are several of the partes
similares (or similar parts § 46) of our bodies, in
which, the knife, and powerfully armed eye of
the anatomist, have not been able to detect the
smallest vestige of nerves, and where neither sur-
gical observations nor live dissections, often re-
peated by the most dextrous hand, have succeeded
in discovering even the faintest phenomena of
sensibility.
In an enumeration of such parts, as appear to
be destitute of sensation and nerves, we must em-
brace, besides the naked cellular membrane, the
epidermis, the reticulum mucosum, the hairs, and
the nails.
K3 We



150 OF THE SENSORIUM
We include further, the cartilages, and bones,
with their periostia and marrow.
To these must be added, the tendons, the aponeu-
roses, and ligaments; as also most of the broader
and more extensive membranes, such, for example,
as the dura mater and tunica arachnoidea; the
pleura, with the mediastinæ and pericardium; the
peritoneum; the cornea, &c.
Under the same head we arrange most parts of
the absorbent system, but more especially the
thoracic duct.
Finally, This catalogue of such parts as neither
possess nerves, nor are endued with sensibility,
shall be closed, by the addition of the secundines,
and umbilical cord.
§ 206.
The primary or nascent origins of the nerves,
emerging from the sensorium itself, have, as yet,
eluded the most zealous researches of the subtle
knife and prying eye of the anatomist: it there-
fore still remains a matter of controversy and
doubt, whether the nerves on each side of the
body derive their origins from the corresponding,
or from the opposite side of the sensorium? Cer-
tain pathological phenomena appear indeed to fa-
vour 

151 AND NERVES.
vour the latter of these opinions. It has been also
lately established by the illustrious Sommering that
a true decussation or crossing of the optic nerves
does actually exist.
§ 207.
A certain continuation of the pia mater accom-
panies the medullary part of the nerves in their
course, in such a manner, as to form for them a
vascular cortex, or covering, of extreme tender-
ness. No sooner, however, do these cords emerge
from the cerebrum, or the spinal marrow, than
they assume a very singular habit and appearance,
by which they may be readily distinguished from
almost all the other similar parts of the body.
This peculiarity of appearance is produced by
small plicæ or folds, which they exhibit, running
in angular directions, more or less oblique. These
folds were formerly described by P. P. Molinel,
who compared them, nor inconsistently with pro-
priety and fitness, to the rugæ of the lumbricus,
or round worm, or to the small rings of the aspera
arteria.
§ 208.
The nerves, especially those of the single or
unpaired orders, such, for instance, as the inter-
costal and vagantes or wandering nerves, are
every where furnished with ganglia, i. e. small
K4 bulbs, 

152 OF THE SENSORIUM
bulbs, of a texture considerably compact, and of
a cineritious colour, somewhat inclining to a pale
red: the functions and uses of these bodies in the
animal economy have not yet been satisfactorily
ascertained and demonstrated. We are, however,
in the mean time, most inclined to adopt the
opinion formerly entertained respecting these sub-
stances by the ingenious Zinn. That acute phy-
siologist believed the ganglia to consist entirely of
mazy complications and intertextures of minute
nervous filaments originating from different sources.
In consequence of this intricate and uninvestigated
texture of these bodies, he conjectured, that each
nervous filament, or thread proceeding from them,
participates, or contains in its composition, a part
of every filament that enters into their structure,
however numerous those filaments may be, or
however different the sources from which they
originate.
§ 209.
Neither does there appear to exist any very
material difference between the nature of ganglia,
as just described, and of what are called plexus
nervosi. These latter are also indebted, for their
existence and form, to a similar concurrence and
anastomosing intertexture of nerves that originate
from different sources. The composition of such
nervous filaments as ramify and proceed from these
plexus 


153 AND NERVES.
plexus nervosi, appears to be also perfectly analo-
gous to the composition of those, that originate
from the ganglia, of which we have already
spoken.
§ 210.
But as the nascent origins of the nerves, so like-
wise (with a few exceptions), the final termina-
tions of their extreme ramuli, or remote filamentary
branches, are as yet involved in the depth of ob-
scurity. For if we except those few nerves that
terminate in a kind of medullary expansion, as the
optic nerve in the retina, and the soft portion of
the seventh pair, in that pulpy zone, contained be-
tween the spiral laminæ of the cochlea of the ear
—If, I say, we except these two nerves, the eva-
nescent filaments of such of the others as enter the
viscera, the muscles, the skin, &c. become so mi-
nutely blended with the real parenchyma of the
parts on which they are distributed, and gradually
assume such a pulpy consistence, that the eye of
the anatomist can no longer trace them through
their mazy courses.
SECT.

154 OF THE NERVOUS SYSTEM.
SECT. XVI.
OF THE FUNCTIONS OF THE NERVOUS SYSTEM
IN GENERAL.
§ 211.
WE have thus seen, that of the sen-
sorium, and nerves so generally and minutely
distributed throughout most parts of the body, a
complete system is beautifully constituted, which,
during the continuance of life, serves as a medium
of communication and mutual intercourse between
the body and the mind.
§ 212.
Various circumstances and phenomena combine
in rendering it probable, that the mind is indeed
attached and closely connected to the brain itself.
That the brain is thus honoured and dignified in
its alliance is very powerfully and strikingly
evidenced, by most of the instruments of sensation
being situated in the very vicinity of that organ;
by the astonishing conformation of its various
parts, considered with regard to their figure and
structure; but more especially by the phenomena
attendant on its morbid affections.
§ 213. 

155 OF THE NERVOUS SYSTEM.
§ 213.
With respect to that connection of which we
have just hinted, I would further observe, that
certain physiologists, wantonly sporting in the de-
lusive fields of imagination, have suffered them-
selves to be so far influenced by the form and
situation of particular parts of the encephalon,
that they have considered, and even endeavoured
to prove, sometimes one, sometimes another of
these parts, to be indeed the very feat, and royal
court, (as it were) of the mind. This honorary
and sublime privilege, of affording a sacred feat
to our nobler and immortal part, some meta-
physical physiologists have been solicitous to
bellow on the pineal gland *, others on the
cerebellum, others on the corpus callosum †, and
* In favour of the Cartesian hypothesis, some degree of
testimony appeared to be derived from the dissections of
certain maniacs, in whom the pineal gland was found in-
vested with calculous concretions. On more accurate ob-
servation, however, it was discovered, that not only in
maniacs, but also in numerous other subjects possessing the
most complete degree of mental sanity, this same glandular
body was surrounded, from about the 12th year of life, by
minute sandy concretions of a pearl-like appearance.—Cl.
Sommering de lapillis vel prope vel intra glandulam pinea-
lem sitis, s. de acernulo cerebri Mogunt. 1785. 8.
† Those fictitious prerogatives both of the cerebellum and
corpus callosum are refuted in a very masterly manner by
Zinn 
 

256 OF THE NERVOUS SYSTEM.
others, again, on that part which has been deno-
minated pons Varolii.
§ 214.
We are not by any means to suppose, that the
whole energy of the nervous system depends on
the encephalon alone; it is also derived in part
from the spinal marrow, and even the nerves
themselves possess such a degree of inherent or
native energy, as is sufficient of itself to throw the
muscles into a state of convulsion. This native or
exclusive energy of the nerves, appears to be
principally supported and preserved by that vas-
cular cortex or covering of those organs, of which
we briefly spoke on a former occasion (§ 205).
It is, however, a truth which ought not to be for-
gotten, that this inherent power of the nerves
themselves is less, and that energy, on the con-
trary, which is derived immediately from the
encephalon, greater, in man, than in other
animals, especially such as are supplied with cold
blood.
§ 215.
The office of the nervous system appears, in a
particular manner, to be two-fold. First, by means
Zinn in his " Experim. circa corpus callosum, cerebellum,
duram meningem, in vivis animalibus institut. Goetting.
1749. 4.
of

157 OF THE NERVOUS SYSTEM. 
of this system, other parts of the body, especially
such muscles as are subjected to the influence of
the will, are excited to motion; of this function,
however, we will treat more fully in another
place. But, secondly, the nerves are peculiarly
subservient to sensation; whatever sensible impres-
sions are made on the body, they, like active he-
ralds, convey and announce immediately to the
sensorium, and there give rise to perception.
§ 216.
Finally, the sensorium is evidently possessed of
the following very singular faculty or power, viz.
that, having received sensible impressions through
the medium and agency of certain nerves, it is
able to re-act again in its turn, not only on the
same nerves, but also on such as are completely
different. In testimony of the truth and authen-
ticity of this position, it will be sufficient to men-
tion the action of the retina, when affected by
light, on the sensorium, and the re-action of this
latter, again, in either constricting or dilating the
iris.
§ 217.
It is principally from this last source, that we
are to derive and explain most of the effects of
the imagination, and passions of the mind, on
the human body: of these effects we will speak
more 


158 OF THE NERVOUS SYSTEM.
more fully on a future occasion. To the same
source, also, must we refer that extensive and
diversified consent of the nervous system, which
prevails throughout almost the whole body (§ 14.),
and the astonishing power and influence of the
same, over most of the other functions of the
animal economy.
§ 2l8.
That the phenomena which we have just men-
tioned, proceed from certain properties essential
to the nervous system, is a position, that appears,
from observation and experiment, to be founded
on the most indubitable evidence. But, to eluci-
date and explain the manner in which this system
acts, in the production of such phenomena, is,
indeed, a difficulty oS the utmost magnitude.
§ 219.
When we view the subject in a general light,
the various opinions, which have at different times
been advanced on this contested point, may be all
referred to two leading classes: one of these
alleges the action of the nervous system, to de-
pend on a certain oscillatory motion; while the
other supposes it to be produced by the motion of
a peculiar fluid, respecting the nature of which
physiologists, again, hold different opinions. Thus,
while some believe this fluid to be animal spirits,
contained 

159 OF THE NERVOUS SYSTEM. 
contained in, and passing through, vessels, others
contend, that it is a certain modification of matter,
similar to fire, electricity, or the magnetic effluvia.
§ 220.
Although I am disposed to adopt neither of
the above opinions as my own, yet it is proper to
observe, that most of the arguments, by which the
advocates of either hypothesis have endeavoured to
invalidate the other, appear to me to be as crude
and inconclusive, as they ought to be subtle, inge-
nious and forcible. This observation applies, as
well to the arguments made use of to prove the
oscillations of the nerves, as to those advanced for
the purpose of establishing the existence of a ner-
vous fluid.
§ 221.
If, indeed, our views of the subject be not erro-
neous, the two foregoing opinions may, without
impropriety, be united, and thus a third one
formed, more plausible, at least, than either of
the originals, namely, that a certain nervous fluid
does actually exist, and that this fluid is also capa-
ble of motion, and of being thrown into oscillatory
vibrations, when subjected to the action and influ-
ence of stimuli.
§ 222. 

160 OF THE NERVOUS SYSTEM.
§ 222.
Not to mention various other evidences, which
might be obviously deduced, from the different
phenomena of the nervous system, the structure of
the brain itself, which bears a striking resemblance
to that of certain secreting viscera, appears indeed
to be highly in favour of the existence of a nervous
fluid. It is surely a matter too obvious to admit
of controversy, that there is no more need of any
direct tubes and canals, for the distribution of
such a fluid through the nerves, than there is, for
the conveyance of a liquid through brown paper,
or any other filtre.
The nugatory calculations, respecting the asto-
nishing rapidity, with which the animal spirits have
been supposed to hurry through their nervous
canals, in all parts of the system, are subjects too
hypothetical and visionary to merit our time, or
command our attention.
§ 223.
That an oscillation of the nerves does indeed
exist, is a position, powerfully supported by a great
variety of very striking and pointed physiological
phenomena. This oscillation must not, however,
be supposed to bear any resemblance to the rude
vibrations of tense chords, but is such a subtle,
tremulous motion, as may be readily conceived to
2 take 

161 OF THE NERVOUS SYSTEM. 
take place in the tender, pulpy substance of the
brain. That hearing is excited by an oscillation
of a liquid, has been reduced to satisfactory de-
monstration. That an oscillatory motion somewhat
similar takes place also, in the act of vision, is
(though we should not be willing to repose impli-
cit confidence in the opinions of Leon. Euler) a
position founded, at least, on strong probabilities.
That the action of the other senses depends also
on an oscillatory motion of a similar nature, is an
opinion, which was not only embraced by the
illustrious Newton *, but has been since ably and
successfully defended in the writings of the saga-
cious Hartley. It is on the principle of the exis-
tence of such a motion, that this last mentioned
author, has first happily accounted for the associ-
ation of ideas, and then, by the aid of this, pro-
ceeded to explain, with the utmost ingenuity, most
of the functions performed by the different facul-
ties of the mind †.
* Vide ejus Quæstiones ad calcem optices. Qu. 23. p.
355. edit. Lond. 1719-8.
† David Hartley's Observations on man, his frame, his
duty, and his expectations. Lond. 1749, vol. ii. 8.
VOL. I. L SECT. 

162 OF THE TOUCH.
SECT. XVII.
OF THE EXTERNAL SENSES IN GENERAL, BUT
PARTICULARLY OF THE TOUCH.
§ 224.
ONE office of the nerves, as we have
already had occasion to observe, consists in com-
municating to the sensorium, impressions made by
external objects. This they do through the me-
dium of the external senses, which officiate as
watchful centinels to the body, and diligent in-
structors to the mind.
These, therefore, shall constitute, at present, the
sole object of our consideration. For to arrange
among the senses, the stimulus or propensity which
animals feel to evacuate their fæces, the sensation
of hunger to which they are subjected, or other
internal calls of nature of a similar kind, would
be, as Haller formerly observed, an unnecessary
species of subtility and refinement.
225.
It ought to be remembered, that no other class
of functions belonging to the animal economy, is
subjected to such an astonishing variety in different
individuals, as that of the external senses, which
constitutes 

163 OF THE TOUCH. 
constitutes the subject of our present consideration.
This infinite diversity, which exists between these
senses in different individuals, is either natural or
acquired, and relates to their greater or less acu-
men or sharpness, their subtlety, or to the manner
in which they are affected by similar applications
of the same stimuli.
§ 226.
In giving an entire and complete account of
the external senses, it appears most proper to
begin with the touch, this being the one which
manifests itself at the earliest period in the human
subject after birth. The organ of the sense of
touch is expanded over the whole superficies of
the body, and is so constituted and formed as to
be affected by much the greatest number of the
properties of external objects.
§ 227.
For we are not only made sensible of certain.
qualities of substances by means of the touch
alone, as of heat, hardness, weight, &c. but there
also exist other qualities, such, for instance, as
figure, distance, &c. of which we acquire, a much
more certain and accurate knowledge by the aid
of the touch, though it must be acknowledged
that these qualities are at the same time subject to
the cognizance of some of the rest of our senses.
L2 § 228. 


164 OF THE TOUCH.
§ 228.
The touch is less liable to deception than the
other senses; and is capable of becoming, by cul-
tivation and attention, so exquisitely perfect and
refined, as to be able to compensate, in a certain
degree, for any deficiency in its sifter senses, more
especially in that of vision.
§ 229.
The organ of this sense is indeed the skin in
general, concerning the fabric and texture of
which we spoke formerly; but those parts that
are more immediately subservient to the touch,
are the papillæ of the corium or cutis vera; these
papillæ exhibit various figures in different parts of
the body; they are indeed, for the most part, ver-
rucose, in other places they are fungous, in others
filamentous or thread-like, &c. under all which ap-
pearances, the extremities of the cutaneous nerves
terminate after the manner of small pulpy pencils.
§ 230.
But by far the most important and distinguished
instruments of the touch are, in particular, the
hands, the skin of which is impressed with a great
number of striking peculiarities. Thus, for ex-
ample, the skin on the palms of the hands, and on
each side of the joints of the fingers, is sulcated
and completely destitute of hair, for the purpose of
facilitating 

165 OF THE TOUCH.
facilitating the folding or doubling up of those
parts. The extremities of the fingers, on their
internal, and of the toes, on their inferior, sur-
faces, are furrowed with slight and very elegant
grooves running in directions more or less spiral:
but the former, on the exterior, and the latter on
the superior, sides, of their terminations, are pro-
tected from injury by nails.
§ 231.
These scutiform nails are possessed only by man,
and a few other animals, (belonging to the class
mammalia), which are also furnished with hands,
and excel in the acuteness of their sense of touch.
These nails appear to be designed for the purpose
of making a gentle resistance to the pressure of
the fingers when examining substances, and thus
aiding their action.
The nails, though of a horny nature, must
nevertheless be considered, on the whole, as pro-
ductions or continuations of the epidermis: for
immediately under them lies the reticulum muco-
sum, which in Æthiopians is black; and finally,
beneath this again is expanded the corium or true
skin, which is firmly attached to the periostium of
the extreme phalanx of the fingers. Also these
constituent parts of the nails are striated in a lon-
gitudinal direction. At their posterior margins
L3 (which 

166 OF THE TASTE.
(which are distinguished by small semilunar seg-
ments, of a shining or somewhat brilliant ap-
pearance) they are securely fixed in a groove
formed by a reflection of the cutis, from whence
by a daily, but very moderate, increase, they are
gradually protruded forward, in such a manner, as
to be completely renovated in every term of about
six months.
SECT. XVIII.
OF THE TASTE.
§ 232.
TASTES are certain impressions made
on, and perceived by, the tongue, and also, in some
measure, by the adjoining cutaneous parts of the os
internum (i.e. the inside of the mouth); these parts
are, in particular, the medium palati, the fauces,
the cheeks, and even the lips themselves; with
respect, however, to the whole of these auxiliary
parts, it is proper to observe, that they have no
perception of any tastes except such as are acrid
or intensely bitter.
§ 233. 

167 OF THE TASTE.
§ 233.
The principal instrument of taste is the tongue,
an organ capable of the utmost agility in motion,
very pliable, and exceedingly changeable in point
of form: it consists of a fleshy texture, which ex-
hibits a striking appearance, somewhat resembling
the texture of the heart.
§ 234.
It is invested with involucra or coverings, which
bear a similitude to the different strata of the cutis:
these are, the epithelion, which corresponds to the
cuticle, the reticulum Malpighianum, and lastly,
a papillary membrane, that differs but little in its
structure from the cerium or true skin.
§ 235.
The principal difference consists in this, that
the epithelion, instead of a fine cutaneous oil, is
lubricated and moistened by mucus, which exsudes
from that imperceptible orifice, named after Mei-
bomius, and also from the rest of that glandular
expansion, discovered by Morgagni: another point
of difference is, the conformation of the papillæ,
which are divided into the petiolated, the obtuse,
and the conical; of these, the former, being very
few in number, are placed in a lunated arrange-
ment, at the root of the tongue, while the others,
being of various size, are crouded promiscuously
L4 and 

168 OF THE TASTE.
and without order, on the back of the tongue,
but more especially on its edges and tip, where
the sense of taste is most acute and exquisite.
§ 236.
To these papillæ pass the extreme filaments of
the lingual branch of the fifth pair of nerves, by
the offices and aid of which it appears probable,
that the sense of taste is proximately generated and
preserved.
For the ninth pair of nerves, and also that
branch of the eighth, which is distributed through-
out the tongue, appear to be subservient to the
various motions performed by that organ in chew-
ing, swallowing, speaking, &c. rather than to its
function as the immediate instrument of taste.
§ 237.
That the tongue may exercise the sense of taste
in perfection, it is necessary for it to be kept in a
state of complete humidity; the substance to be
tasted should also be a liquid, and ought to abound
with salts in a state of solution: for if either the
tongue itself, or the substances applied to it be
dry, it may then indeed examine them by the
touch, which it generally possesses in an exquisite
degree, but cannot with strictness and propriety
be said to taste them.
When

169 OF SMELLING.
When the tongue discharges the office of
tasting with most perfection and acuteness, the
papillæ, situated on its apex and edges, appear to
be brought into a state of genuine, though slight,
erection.
SECT. XIX.
OF SMELLING.
§ 238.
BY means of the sense of smelling we
perceive impressions made by the odorous effluvia
of substances, which being inhaled in inspiration,
come in contact with that part, in particular, of
the Schneiderian membrane, which invests each
side of the septum narium, and lines the convex
surfaces of the concha.
§ 239.
For although the whole of the internal nares,
together with the adjoining sinuses, which open
into them, be lined with a humid membrane,
similar in appearance to the Schneiderian, it
nevertheless appears to be diversied in its nature
in different places.
That part of the membrane, which is situated
near the opening of the external nares themselves,
bearing 

170 OF SMELLING.
bearing a stronger resemblance to the other parts
of the real cutis, is overspread with sebaceous fol-
licles, which are completely mantled in clusters of
hair.
But that part which lines the septum narium,
and conchæ, is of a fungous nature, and abounds
with small muciferous cryptæ or cells.
Finally, Those portions which invest the
parietes of the frontal, the sphenoidal, the eth-
moidal, and the maxillary sinuses, are by far the
most tender and delicate of all, and are completely
overspread with an infinitude of minute blood-
vessels, which constantly exhale from their ex-
tremities a subtle dew-like fluid of an aqueous
nature.
§ 240.
The principal, if not, indeed, the only use of
those sinuses appears, therefore, to be, to furnish
a watery liquid, of such a nature, as has been just
described, which being first conveyed into the
three passages or avenues of the nares, may be
from thence communicated to those adjacent parts,
which, we have already said, constitute the imme-
diate instruments of the sense of smelling. By
thus supplying, with a due degree of humidity,
the parts which proximately form the olfactory
organs, 

171 OF SMELLING.
organs, those sinuses contribute, not a little, to
preserve the acuteness and perfection of this in-
teresting sense.
For the attainment of this end, such a wise pro-
vision is made by the very situation of those several
sinuses, that in whatever position the head be
suffered to rest, one or other of them may still
discharge and deposit a quantity of this subtle dew,
on the immediate feat of the sense of smelling.
§ 241.
The fungous part of the nasal membrane, of
which we have already spoken, and which con-
stitutes the proximate organ of smelling, besides,
the immense number of minute blood-vessels with
which it is overspread (and which are rendered in
a particular manner remarkable, by this circum-
stance, that there are no other vessels in the whole
body equally liable to spontaneous hemorrhages);
besides these small blood-vessels, I say, this part
of the membrane is also furnished with nerves,
especially from the first pair, and also from both
branches of the fifth pair: of these, the first pair
appears to be of itself solely subservient to the sense
of smelling; while the others supply the parts, to
which they are distributed, with branches for the
purposes of common sensation, such, for example,
as that which gives rise to sneezing, &c.
§ 242. 
 

172 OF SMELLING.
§ 242.
The extreme filaments of this first pair of nerves
are not, (as is the case in the organs of touch and
taste), lengthened out and rounded into papillary
elongations, but appear to deliquate, or melt down,
as it were, into the spongy and uniform paren-
chyma of the membrane in which they terminate.
§ 243.
In new-born infants, the chamber destined for 
the immediate reception of odours is narrow, and
as yet extremely imperfect. The sinuses, of which
we have already spoken, have at this time scarcely
made their appearance: hence, infants do not ac-
quire the sense of smelling till a late period, as the
expansion and complete formation of their internal
nares are but gradually and very slowly accom-
plished. The larger those instruments become,
and the more accurately they are formed and
finished, the more exquisite will be the acuteness
and perfection of this sense.
§ 244.
Finally, it is a truth well worthy of being re-
membered, that there is scarcely another external
sense, which possesses such a powerful connection
with, and influence over, both the sensorium itself,
and the internal senses, as that of smelling.
There 

173 OF HEARING. 
There is none subject to such striking diosyn-
crasies; none better calculated either to produce,
to prevent, or to remove, paroxysms of fainting.
Neither is there any one susceptible of more
delicate and pleasing impressions; the smell is,
therefore, happily termed by Rousseau the sense
of the imagination.
Nor are there, lastly, any other species of sen-
sations that appear to excite so clear and vivid a
remembrance, as that which specific odours recal
to the memory.
SECT. XX.
OF HEARING.
§ 244.
SOUND, which is excited by a tremu-
lous collision of elastic substances, and propagated
from sonorous bodies, through the medium of the
air, is at length perceived by the sense of hearing,
after having proceeded onward in the following
order: viz. it is first received by a shell-formed
cartilage denominated the external ear, over which
a few

174 OF HEARING.
a few of the human species possess a power of
voluntary motion: being collected and concen-
trated, as it were, by means of this concha or shell,
it passes immediately into the meatus auditorius,
which is thoroughly anointed and defended by a
very bitter and somewhat yellowish cerumen, or
wax-like substance: at the internal extremity of
this meatus auditorius it strikes against the mem-
brana tympani, which is situated in an oblique
position, is firmly attached to an annular groove
in the os temporis, and forms a complete partition
between this meatus auditorius, or passage for
found, and the middle portion of the ear.
§ 246.
Behind this membrane, the middle portion of
the ear, denominated the cavity of the tympanum,
is so situated as to have its fundus or bottom
pointing upwards and inwards.
It contains three small bones, belonging to the
organ of hearing, the external of which, called
the malleus, is connected by its handle to the mem-
brane of the tympanum; from its spinous process,
which runs in a forward direction, a bulb or globe
is formed, (especially in an adult subject), with an
annular groove surrounding its base; this small
globular head rests on the body of the incus.
The

175 OF HEARING.
The incus itself is attached to the minute knob
or head of the stapes, by its longer process, which
extends nearly to the middle of the cavity of the
tympanum.
Finally, the stapes, resting its basis on the fenes-
tra ovalis, looks towards the vestibulum of the
labyrinth, into which, found, having percussated
against the membrane of the tympanum, is propa-
gated by means of the connections of those three
osiccula or small bones.
§ 247.
The Eustachean tube, running from the interior
parts of the fauces, opens also into the cavity of
the tympanum; the inferior winding passage of
the cochlea enters likewise into the same cavity;
over the mouth or orifice of this passage, called
the fenestra rotunda, a fine membrane of a peculiar
nature is expanded. Physiologists have not yet
ascertained and demonstrated, in a clear and satis-
factory manner, the uses of either of those two last
mentioned parts.
§ 248.
Lastly, in the deep and hidden recesses of the
os petrosum lies the labyrinth, or internal portion of
the ear, which embraces again three several parts.
These

176 OF HEARING.
These are the vestibulum, which is situated in
the middle between the other two, and into which
open, besides the fenestra ovalis, both the five
mouths of the semicircular canals that run in a
backward direction, and also the superior winding
passage of the cochlea, which extends and lies
anteriorly.
§ 249.
The labyrinth itself contains a very subtle, lim-
pid water, which has been named after the illus-
trious Cotunnius, and which that celebrated phy-
siologist discovered to be absorbed by two very
minute canals: these small canals, called by Co-
tunnius, aqueducts, (and by Meckel diverticula),
arise, the one from the vestibulum itself, the other
from the inferior winding passage of the cochlea.
§ 250.
The soft portion of the seventh pair of nerves,
together with the hard, (which afterwards passes
through the aqueduct of Fallopius), having en-
tered the internal chamber of hearing, transmits
its medullary filaments through the perforated
bottom of that cavity. These filaments pass, in
part, to the vestibulum and semicircular canals,
but are distributed more especially over the base
of the cochlea, where their extremities are ar-
ranged in such a manner as to run between the
2 laminæ 

177 OF HEARING. 
laminæ or plates of the septum of the cochlea,
exhibiting the appearance of a fine medullary
zone, beautifully ornamented with plexiform striæ
or streaks.
§ 251.
The oscillatory tremor which we formerly traced
and followed up, even to the fenestra ovalis,
(§ 246.), is from thence propagated to the vesti-
bulum, where, finally, through the medium of the
subtle aqueous liquid already described (§ 249.),
it strikes and impresses the auditory nerves them-
selves, which are distributed with infinite art and
ingenuity throughout the mazy circumvolutions
of the labyrinth.
§ 252.
The impetus of found, striking against the mem-
brane, and being propagated through the cavity
of the tympanum, is thought to be modified and
regulated, not only by the muscles of the malleus
and stapes, which appear, in their contraction and
relaxation to be subject to the influence of the
will, but also by the chorda tympani, which is
situated in the middle, between the handle of the
malleus and the longer leg of the incus.
VOL. I. M SECT. 

178 OF VISION.
SECT. XXI.
OF VISION.
§ 253.
THOSE rolling or versatile globes,
denominated eyes, are to be considered as the im-
mediate instruments of the sublime sense of vision.
They are fixed as if on footstalks, by their optic
nerves (respecting the decussation of which we
have already spoken, § 205.), in such a manner,
that their insertions are not directly opposite to
the centres of the cornea and iris, but are placed
behind the imaginary axes of the eyes, in situa-
tions somewhat nearer to the nose.
§ 254.
Each orb is composed of various tunics or coats,
which inclose humours of different densities, and
so extremely pellucid, that the rays of light,
having entered the pupil or window in the ante-
rior segment of the orb, can pass through, with-
out the least interruption, to its bottom or opposite
side.
§ 255.
The external involucrum of the globe of the eye
is called sclerotica, the anterior hiatus or chasm of
which 

179 OF VISION. 
which is closed up by the transparent cornea,
which is a lamellated membrane, more or less
convex, and projects in a slight degree forward,
like a segment of a smaller globe protruding out
of a larger.
§ 256.
Next to the sclerotica lies the tunica choroidea,
which abounds in blood-vessels, more especially
in verticose or circuitous veins: this coat is stained
on each side by a black pigment, which loosely
adheres to its concave surface after the manner,
and with the appearance, of mucus.
§ 257.
The choroides encloses, finally, the retina,
which is the most internal of the common tunics
embracing the visual orb. This coat consists en-
tirely of the medullary substance of the optic
nerve, which having perforated the sclerotica and
and choroidea, is expanded on the concave sur-
face of this last involucrum, and there arranged
with the utmost beauty and elegance of structure.
§ 258.
The anterior border of the tunica choroidea
terminates in a cellular ring, which is denominated
orbiculus ciliaris, and by means of which the cho-
roides is more firmly attached to a corresponding
M2 groove 

180 OF VISION.
groove or depression in the sclerotica. From this
cellular girdle or attachment, two other membranes
of different kinds, (namely, the iris and ciliary
processes), originate and diverge from each other,
like two expanded circles.
§ 259.
The iris (the posterior surface of which, being
overspread with a dark pigment, is denominated
uvea) is situated anteriorly, is gently convex on
the surface next the cornea, and is surrounded on
all sides by a humour of an aqueous nature. That
segment of the iris, which lies next the nose is
narrower, while that which looks towards the
temples is possessed of greater expansion. Its tex-
ture consists entirely of condensed cellular mem-
brane, without the smallest vestige of muscular
fibres; upon the whole, it appears to be in reality
a membrane sui generis, as was formerly well
observed by Zinn, and not by any means an ap-
pendage to the choroides. On its anterior surface
it is differently coloured in different individuals,
and while distended and animated with a plenitude
of life, it exhibits somewhat of a floccose ap-
pearance.
§ 260.
The blood-vessels of the iris run principally on
its anterior surface, and, in the fœtus, are con-
tinued 

181 OF VISION. 
tinued into what is called the membrana pupillaris:
respecting the nature and use of this membrane, I
have spoken more fully in another place *. It
appears to be intended for the purpose of pre-
serving the iris, (during the rapid growth of the
ball of the eye), in a state of expansion, and thus
rendering it more fit for future motion.
About the seventh or eighth month of preg-
nancy, when the ball of the eye has now acquired
a considerable magnitude, this membrane begins
to open and give way in its centre; the elliptical
arches of its vessels are retracted in a very gradual
manner, and thus form, in my opinion, the small
interior ring of the iris; it is, at least, certain, that
not a single trait of this ring can be discovered in
the eyes of a fœtus previously to the above-men-
tioned period.
§ 261.
The posterior of those two orbicular membranes,
of which we have already spoken, (§ 258) is
called the ciliary body or band; it runs in a back-
ward direction, and therefore, in its progress,
diverges still farther from the iris; by its external
border, which is gross and firm, it is attached to
the orbiculis ciliaris (§ 258), but by its internal,
* Commentat. societ. scient. Goettingens. T. VII.
M3 which 

182 OF VISION.
which is more fine and delicate, it embraces the
margin of the capsule of the lens: it is also shaded
with that same dusky pigment, of which we have
twice already spoken.
Its anterior surface, lying opposed to the uvea,
is somewhat striated.
Its posterior surface, resting on the vitreous
substance, is distinguished by about seventy plicæ
or folds, which exhibit an extremely elegant
floccose appearance; these are called ciliary pro-
cesses, and are remarkable for a vascular apparatus
of inexpressible subtlety and beauty.
§ 262.
In the eye-ball itself, the membranes of which
we have been hitherto describing, there are en-
closed, in particular, three different humours.
The vitreous humour occupies and fills the
posterior, and by far, the greatest, portion of the
visual orb. It is distributed, in a countless number
of minute drops, throughout as many minute cells
of the membrana hyaloidea, in such a manner, that
the whole mass, consisting, in part, of membrane,
and in part, of lymph, exhibits the appearance of
a peculiar, tremulous jelly.
§ 263. 

183 OF VISION. 
§ 263.
The anterior part of this vitreous substance,
has appended to itself, and embraces, in the ciliary
girdle, a capsule, in which is contained the chrys-
taline lens, surrounded on all sides by a very
subtle water, first discovered and described by
Morgagni.
This lens itself, is also composed of extremely
pellucid cellular membrane; it is by far more
dense than the vitreous substance, and is furnished
with so minute a quantity of genuine humour,
that, when pressed between the fingers, it resembles
glue of the most tenacious consistence, but at the
same time of astonishing transparency.
§ 264.
The remaining portion of the internal cavity of
the eye, is filled up by an exceedingly limpid
aqueous humour, and, by the expanded orbicular
curtain of the iris, is divided into two chambers:
these are, the anterior, or more capacious cham-
ber, which separates the cornea from the iris, and
the posterior one, of smaller dimensions, extending
from the uvea to the corpus ciliare.
§ 265.
These most precious and inestimable parts of
the body, as Pliny, the elder, has emphatically
M4 called 

l84 OF VISION.
called the eyes, are securely protected from ex-
ternal injuries, as well by their recluse situations
in their orbits, as by their valviform coverings,
the palpebræ.
Between the folds of the palpebræ are planted,
in immense profusion, the crouded sebaceous fol-
licles of Meibomius; their extreme or lower edges,
fringed with three or four phalanges of cilia or
lashes, are kept in an expanded state by certain
cartilages called tarsi, which are also of further
service in facilitating the motion of the palpebræ 
on the eye-balls.
But (to adopt the language of the eloquent
Cicero) the parts situated immediately above the
palbebræ, being closely mantled in the supercilia
or eye-brows intercept and turn aside the sweat
flowing down in streamlets from the head and face,
and also serve to moderate, in a certain degree,
the excessive effulgence of light.
§ 266.
For the purposes of lubricating the eyes, of
preserving their splendor, and of washing out he-
terogeneous substances, the tears are provided:
the principal source of this fluid is a small conglo-
merate gland, deeply situated in a depression to-
wards the external part of the circumference of
the

185 OF VISION.
the orbit. The excretory ducts belonging to this
gland are numerous, but extremely tender; they
are supposed to convey, from both eyes, in the
course of twenty-four hours, about two ounces of
tears; After having been excreted, the tears are
again absorbed by the puncta lacrymalia, from
whence they are conducted through what are
called the cornua limacum, or snail's horns, to the
lachrymal sac, and from thence finally discharged
into the lowermost passage of the nares.
§ 267.
Thus much it was necessary to premise respect-
ing the admirable structure of the visual organ.
We come now to treat of the functions of this
organ, or, in other words, to consider the doctrine
of vision.
All the rays of light which fall on the convex
surface of the cornea pass through it, provided
their angle of incidence be less than that of 48
degrees. In consequence, not only of the den-
sity, but also the figure of the aqueous humour,
the rays are refracted in that medium, and turned
a little nearer to the real axis.
As many of the rays as, having passed through
the pupil, enter the crystalline lens, must neces-
sarily, 


186 OF VISION.
sarily, in this more dense medium, be subjected
to a still higher degree of refraction.
But by means of the more attenuated and less
refractive vitreous medium, wise provision is made
to prevent these rays from uniting in a focal point
at too short a distance: this point, being thus
farther removed from the convex surface of the
cornea, falls on the retina, and there exhibits, in
an inverted position, the images of all objects
presented, and that in perfect correspondence to
the nature of surrounding and attendant circum-
stances.
§ 268.
This difference in the density of the refracting
media of the eye, exhibits a very striking instance
of the exquisite and inimitable workmanship of the
divine creator. By means of this diversity, such
a complete remedy is provided against the two-
fold separation or divergency of the rays of light,
(the one arising from the different refrangibility
of the different coloured rays, the other from the
very figure of the lenses), that they are all finally
collected and united in the same focal point.
§ 269.
The celebrated problem, in which the cause is
demanded, wherefore we see those objects erect,
the 
 

187 OF VISION. 
the images of which are nevertheless exhibited in
an inverted position on the retina? appears to
admit of an easy solution, when we consider, that
objects are said to be inverted, only from the
relation they bear to others, which are exhibited
in an erect position.
In as much then as the images, not of a few,
but of all objects, even of our own bodies, are
received by the retina in the same relative position,
the situations and relations of the whole of them
harmonize and correspond to one another, equally
as well, as they could possibly have done, had
their positions been truly erect: in consequence
of this, the mind, (which does not attend to the
image itself, but to the sensation excited by its
impression), is sufficiently guarded against embar-
rassment and mistake.
§ 270.
In as much as the conditions, essentially neces-
sary for the purposes of acute and distinct vision,
are extremely numerous and varied, the creator of
man has made the wisest provision for these, by
endowing the part, subservient to this sublime
sense, with a great variety of functions.
As a certain adequate, but yet definite, quantity,
and not too potent a glare, of light, is essential
to 

188 OF VISION.
to the existence of clear and perfect vision, a two-
fold caution is thus taken; first, to admit, (ac-
cording as the light is stronger or weaker), a
greater or less column of rays to fall on the lens;
and secondly, that all superfluous rays which enter
the eye, and tend only to dazzle by the intensity
of their splendour, be absorbed and rendered
inactive.
The former of these purposes is effectually ac-
complished by the motion of the iris; the latter,
by means of the black pigment.
§ 271.
The iris possesses an atonishing mobility, by
which it accommodates itself so perfectly to the
quantity of light acting on it, that when exposed
to a more intense glare, it is immediately expanded,
and thus diminishes the size of the pupil, but when
subjected to the action of a weaker light, it is
again retracted, and the pupil consequently en-
larged.
Physiologists have attempted a satisfactory ex-
planation of this motion, in a variety of modes,
sounded on different principles; by some it has
been derived from diversified impulses of the blood
on the tender vessels of the moving part, while
others have figured to themselves the existence of
certain 

189 OF VISION. 
certain imaginary muscles in the iris, and have
committed to them the whole of the phenomenon
in question, &c. But I have lately made it appear
in a separate paper, that neither of these modes
of explanation is well founded, but that it is much
more agreeable to evidence, and correspondent to
the phenomena of nature, to derive the immediate
cause of the motion of the iris from its vita pro-
pria, or specific life. (§ 47.) The more remote
cause of this motion, as we observed on a former
occasion (§ 256), cannot be referred to any other
source, than the re-action of the sensorium itself.
§ 272.
The function of this dusky pigment, of which
we have already so repeatedly spoken (§ 256,
259, 261,) to wit, that it is destined to absorb
the superfluous rays of light, and is hence of the
utmost importance in the business of perfect vision,
may, besides other arguments, be safely inferred
from dissections of the eyes of various animals;
but is more completely demonstrated and estab-
lished, by the morbid constitution of the white
Æthiopians, or Albinos, as they are called, in
whom, from a deficiency of this pigment, the
organs of vision are painfully tender, and the im-
pulse of light consequently too powerful to be
borne.
§ 273.

190 OF VISION.
§ 273.
It is further requisite, that the focus of re-
fracted rays be perfectly formed on the retina, so
that it may strike the very point of vision, and be
neither so far extended as to fall behind it, nor so
much contracted as to terminate before it, in the
vitreous substance.
The latter of these deviations from perfect
vision is what takes place in those individuals
called myopes, in whom the lucid cornea is rather
too convex and gibbous.
But the former deviation is that under which
the presbytæ labour, as the conformation of the
anterior parts of the eyes is directly the reverse.
§ 274.
But as an eye perfectly found is able to discern,
with equal distinctness, bodies, whether at a
greater or less distance, it must, without doubt,
be furnished with peculiar faculties or powers of
accommodating itself to the various distances of
objects. That these internal and accommodating
changes of the eye, are in a great measure pro-
duced by the pressure of the recti muscles on the
ball which they embrace, is a position so clear,
and apparently well founded, as scarcely to admit
of a doubt. Besides other arguments which might
be 
 

191 OF VISION. 
be advanced in favour of this opinion, I am
induced to adopt it in consideration of the very
singular structure, and extreme flexility, of the
sclerotica, in the eye of the Greenland phoca, or
sea-calf. By this peculiarity of fabrication and
arrangement, nature has made the most exquisite
provision to enable this amphibious animal to
enjoy at all times, the advantages of vision,
though passing its life alternately in media of very
different densities.
§ 275.
By means of these same muscles, our eyes,
whilst we are awake, are perpetually agitated,
although with an almost insensible motion, and so
directed as to have their visual axes arranged in
right lines with the objects viewed. For although
the whole of the retina be possessed of sensibility,
yet it is not in every part equally well adapted to
receive the images of objects.
For at the genuine axis of the eye-ball, in the
place, for example, where the optic nerve enters,
it appears, from the well-known and celebrated
experiment of Mariotte, that the human eye is
destitute of the power of vision.
But the principal focus of the retina, and that
which ought to be considered as the leading and
4 immediate 

192 OF VISION.
immediate instrument of distinct vision, is, situated
in an imaginary axis of the eye-ball, which is sup-
posed to pass through the centre of the cornea,
and to be thus continued through the centre of
the whole orb. It is not, however, (as was lately
observed by the celebrated Kæstner in his com-
ments on certain works of Boerhaave), to be
from hence understood, that we are unable to see
clearly and distinctly, more than one single point
of an object while the eye remains perfectly at
rest, and that we are obliged to shift or alter its
axis in order to distinguish any other point. The
case is quite otherwise, because the sensation pro-
duced by one entire object, is also itself, like its
original, or exciting cause, one and entire.
§ 276.
The habit of directing the axis of the eye with
dispatch and facility towards the object of vision,
is finally acquired only by use and daily exercise.
That this is a position founded in truth, is demon-
strated not only by the example of such individuals
as, having been born blind, acquired afterwards
the power of vision in adult age, but also by that
of tender infants, who seldom attain to this happy
facility of moving their eyes previously to the
third month after birth.
2 § 277.

193 OF VISION.
§ 277.
To the same power of custom and habit, must
we also attribute the remarkable circumstance of
our seeing objects only single, though our eyes be
two in number. New-born infants appear to see
objects double, and double vision, which fre-
quently continues sometime after certain diseases
of the eyes, may be at length overcome and re-
moved by use and exercise.
§ 278.
The joint power of both eyes, with regard to
the acumen and strength of vision, does not,
according to the calculation of Jurin, exceed that
of one eye, more than a thirteenth part.
And, agreeably to an observation, long since
made by that celebrated painter Leon. da Vinci,
it is much best in judging of the distances of
objects to make use of one eye only.
§ 279.
Finally, In treating of the strength and per-
fection of the eye, our former illustrious country-
man, Tob. Mayer, demonstrated, by a series of
very elegant and ingenious experiments, that the
angle of vision ought to exceed, in dimensions, at
least 34 seconds of a degree. From hence he at
the same time illustrated and proved the extreme
VOL. I. N perfection 


194 OF VISION.
perfection of the human eye, because this extent
of the angle of vision may continue nearly the
same, under any light whatever, whether that of
the meridian sun, or that of a weak lamp, so that
though the window or pupil of the eye be greatly
contracted and diminished, yet the clearness of
vision can, from that source, be scarcely in any
degree affected.
§ 280.
From hence we may infer, the inconceivable 
smallness of the images of objects which are thrown
and delineated on the retina, and which are never-
theless impressed with so much force, that, under
certain circumstances, vestiges of them remain a
considerable time, even after the objects them-
selves have been entirely removed from the eye.
SECT. 

195 OF THE INTERNAL SENSES. 
SECT. XXII.
OF THE INTERNAL SENSES, AND OTHER FACULTIES
OF THE MIND.
§ 281
THROUGH the medium of those ex-
ternal senses, of which we have hitherto treated,
ideas are conveyed to our nobler part, the mind;
for, agreeably to the tenor and spirit of a well-
known theorem, nothing can enter the under-
standing save by the route or avenue of the senses.
§ 282.
For the purposes of receiving and preserv-
ing the ideas thus acquired, by the aid of the
senses, and also for making the best use and im-
provement of the intellectual stock received, va-
rious faculties of the mind contribute their united
exertions. Though these faculties be, (as we
have already had occasion to observe, § 42.),
widely different from the vital energies which
reside in the body, nevertheless, by means of the
nervous system, they are so closely connected with
those corporeal energies, that an astonishing in-
tercourse is thus established and supported between
the body and mind, (§ 211.)
N2 § 283. 
 

196 OF THE INTERNAL SENSES.
§ 283.
The first of those powers, possessing indeed,
apparently, the lowest grade, is the faculty of
perception, by means of which the mind is ren-
dered conscious of impressions made on the dif-
ferent organs of sense.
§ 284.
This faculty is aided by another, of better rank
and higher dignity, namely, attention, which so
directs and determines the mind towards any idea
when once excited, as to rivet its thoughts to that
object alone.
§ 285.
For the important purposes of preserving ideas,
which have been already perceived, of re-exciting
them, and associating them into more lively and
picturesque species of imagery, two other faculties,
called internal senses, are brought into action: 
these are memory and imagination, two powers,
which, though nearly allied to each other, may,
notwithstanding, be readily distinguished by the
following characters: memory appears to be more
subservient to, and engaged in, the reception and
retention of arbitrary signs of things; whereas,
imagination, on the contrary, wakes up rather the
very images of things, bestows on them form and
colouring, and marshals them under the view of
the

197 OF THE INTERNAL SENSES. 
the mind, as if the objects themselves were again
actually present: this faculty is more particularly
and powerfully exercised on such objects as are
calculated to excite sensations of pleasure or disgust.
§ 286.
Upon the whole, the faculty of choosing and
refusing, and, (when we consider the matter a
little more minutely), even the foundation of the
whole will itself, appear to rest and depend en-
tirely on certain agreeable and disagreeable varie-
ties of sensation.
§ 287.
From the same prolific source, namely, the
imagination, are also to be derived the affections
or commotions of the mind, to which we see dif-
ferent individuals variously subjected, in confor-
mity to the countless diversities of existing tempe-
raments (§ 59.) The very intimate and instan-
taneous consent of these affections with certain
functions of the body, appears strikingly evident
in an infinitude of examples; thus, for instance,
there is scarcely a single passion of the mind, which
does not possess considerable influence over the
motion of the heart, the appetite for food, and the
powers of digestion,—not to descend to a minute
specification of particular effects, such, for exam-
ple, as the action of shame in giving rise to
N3 blushing, 

198 OF THE INTERNAL SENSES.
blushing, the action of love or hatred on the organs
which serve to distinguish the sexes, the action of
anger on the secretion of bile, &c. &c.
While speaking of the effects produced in the
economy of the human body, by the commotions
of the mind, it is proper to observe, that they
may be divided into stimulant and sedative, or
into those which excite, and those which depress.
Of the former description are joy, love, hope,
anger, &c.
Of the latter, fear, sorrow, nostalgia, and other
species of permanent desire or longing, terror,
envy, &c.
§ 288.
Those faculties of the mind hitherto enume-
rated, are observed to exist in brutes as well as
man, though the latter undoubtedly possesses them
in by far the highest degrees of strength and per-
fection: thus, for example, in none of the inferior
animals do we discover a memory so extensive in
its range, and so powerful in its tenacity; in none
do we discover such a splendid brilliancy, and
glowing warmth of imagination; in none do we
discover such an unbounded, and sometimes fatal,
vehemence of mental passions, &c.
§ 289.

199 OF THE INTERNAL SENSES.
§ 289.
The leading prerogative of the human mind,
consists in this, that it alone possesses the exclusive
power of reason, by means of which it is able to
judge, to form abstract ideas, &c. and which exerts
also the greatest influence over most of the other
faculties of the mind. In place of this divine
power, other animals are endowed with various
instincts, or blind and involuntary impulses, which
lead them to the performance of such actions, as
are suitable to their several economies and modes
of life. Of these instinctive impulses man, on the
other hand, is furnished with scarcely any, save
that which prompts him to participate in venereal
gratifications.
§ 290.
The immense and striking difference between
animal instinct and human reason, will appear
glaring as the noon-day light to him who considers:
That instincts are faculties co-eval with birth,
whereas, on the other hand, the use of reason is
acquired only by culture and education:
That instincts remain stationary, and admit of
no improvement, whereas the expansive improve-
ment and exercise of reason, are literally free from
circumscription:
N4 That 

200 OF THE INTERNAL SENSES.
That instincts are suited only to the destined
mode of life, to the climate, &c. of each species
of animals, and, on this account, are not adequate
to the exigencies of man, who, confined to no
climate, exclusively restricted to no mode of life,
is destined to be an inhabitant of the world at
large: from which boundless and splendid prero-
gative, an inconceivable diversity of wants arise,
which simple instinct is too weak!—far too weak
to supply! but which, the powers of reason, from
resources equally diversified as the emergencies
themselves, are able to satisfy, in the most ample
and complete manner.
Lastly, another high prerogative of man, de-
pending on the powers and exercise of his reason,
is the use of speech, of which we have briefly
spoken on a former occasion (§ 154.) This in-
valuable privilege is the exclusive boast of man
alone, brutes being only furnished with voice, or
a power of emitting sound.
SECT. 


201 OF VOLUNTARY ACTIONS. 
SECT. XXIII.
OF THOSE ACTIONS OF THE BODY WHICH ARE
SUBJECT TO THE POWER OF THE WILL.
§ 291.
THE nerves, as we have already seen,
are so constituted as to perform two different
functions (§ 215), namely, sensation and motion.
The doctrine of the former we have already con-
sidered. It yet remains to add a few observations
on the subject of the latter.
§ 292.
The motions in general of the several parts
of the human body, are usually divided into two
classes, one of which is excited and governed by
the power of the will, while the other is not in
any measure subject to its influence, or controul.
For examples of the latter class, physiologists
commonly refer to the harmonious action of the
heart, and likewise to the peristaltic motion of the
intestines and certain other viscera, &c.
Instances 

202 OF VOLUNTARY ACTIONS.
Instances of the former class we have in the
motions of by far the greater part of the other
muscles of the body.
Doubts are still entertained, with respect to the
real nature of certain motions which take place in
the human system; such as the motions in respira-
tion, in sneezing, in the tension of the membrana
tympani, &c. These are by some classed with the
voluntary, by others with the involuntary, while
others again refer them to a third class, called
mixed motions.
§ 293.
When this division, however, is considered with
a little more steadiness and attention, it is easily
perceived to be embarrassed with such momen-
tous difficulties, that it is scarcely possible to
ascertain, and mark, with definitude, the precise
limits between the classes.
For, on the one hand, a few of the functions
of our bodies, over which the will, unassisted by
other powers, may be said to possess no command
at all, may notwithstanding be excited and brought
into action, when the imagination and passions of
the mind act in concert with the will.
On 

203 OF VOLUNTARY ACTIONS. 
On the other hand there are not wanting
instances of muscular functions, which, though
naturally subject to the immediate command of
the will, have, notwithstanding, been rendered in
a great measure involuntary, by the plastic power
of custom, (the influence aud energetic agency of
which, on animal motions, are indeed of the
utmost moment and importance.)
§ 294.
Of this latter description are those kinds of
muscular motion, which, although at other times
subject to the controul of the will, yet, under
certain circumstances, take place not only without
the consciousness, but even contrary to the incli-
nation of the mind.
Thus, for example, we wink contrary to our
determination, when the finger of a friend is
hastily approached towards our eye, although it
does not touch it; and in most persons, the flexion
of the little finger is usually attended with a syn-
chronous flexion of the ring finger, though a de-
termination had been formed to preserve the latter
entirely unbent.
Without the consciousness of the mind we fre-
quently move our limbs, even when wrapt in the
most profound sleep.
There 

204 OF VOLUNTARY ACTIONS.
There are, on the other hand, examples of
muscles, which, although for the most part per-
fectly obedient to the will, yet in certain cases
refuse to obey its commands. To this head we
may refer the difficulty of describing, by syn-
chronous movements, circles in contrary directions,
with the hand and foot of the same side, together
with other motions of a simiilar nature, which,
although truly voluntary, and extremely easy
when practised alone, are, notwithstanding, per-
formed with the utmost difficulty, if an attempt
be made to associate them with certain other 
motions.
§ 295.
With respect to those motions, which physio-
logists suppose to be perfectly exempt from the
influence of the will, I know of none which can
be clearly and unexceptionably referred to this
head, save the spasms of the uterus in the labour
of parturition.
With respect to the pulsation of the heart, a
very remarkable account stands on record of a
British colonel, who possessed a power of sus-
pending, at pleasure, the motion of both the heart
and arteries. In confirmation of the truth of this,
we have the public testimony of Baynard and
Cheyne, two physicians of the highest reputation 
and

205 OF VOLUNRARY ACTIONS. 
and veracity, who were themselves witnesses to
the astonishing phenomenon.
That the motion of the stomach may be volun-
tary, (as indeed the process of rumination in
general seems to evince), I had once an oppor-
tunity of ascertaining, to my entire satisfaction, in a
ruminating human subject, in whom this retrogade
or reverted motion of the stomach, was under the
most perfect subjection to the command of the
will.
Although the motion of the iris be involuntary,
in by far the greater part of the human race, I
have, notwithstanding, been favoured with an
account, sufficiently authenticated, of a man, who
possessed a power of voluntary command over this
membrane, in such a manner, as to be able, by a
very singular effort, to contract the pupil of the
eye even in a weak and dull light.
There are indeed a great variety of motions,
which, though generally performed without the
influence of the mind, are nevertheless voluntary
in certain individuals, especially if a high degree
of attention, and a vigorous effort of imagination
be excited. Thus, I have known men, who were
able at any moment, to produce and exhibit on
themselves a spasmodic horripilation of the skin,
and

206 OF VOLUNTARY ACTIONS.
and also to renew and completely revive in
themselves the ideas or perception of certain disa-
greeable sensations.
§ 296.
Perhaps those phenomena may be satisfactorily
explained from the re-action of the sensorium,
which appears to be indeed as powerfully excited
by means of the imagination waking up and
exhibiting before it, the image of an active
stimulus, as by the stimulus itself, when impressing
it by its actual presence. There are indeed an
infinitude of phenomena of the animal economy,
which admirably correspond to this explanation;
as the various causes, for example, which excite
erections of the male penis, &c.
§ 297.
With regard to voluntary motions in general,
it may be proper finally to observe, that they are
among the primary and leading characteristics
which serve to distinguish the animal from the
vegetable kingdom; for, as on the one hand, a
power of voluntary motion is never observed to
be possessed by any plant, so on the other, such a
power constitutes an essential attribute of even the
most simple and imperfect genera of animals.
§ 298. 

207 OF MUSCULAR MOTION. 
§ 298.
In our own systems, the voluntary motions fur-
nish the most full and striking evidence, of that
intimate and truly astonishing harmony, which
subsists between the mind and the body. Of the
existence of this harmony every one will be con-
vinced, who considers with attention, the amazing
celerity with which such diversied motions succeed
each other, in the fingers of an able and skillful
performer on the violin, or in our organs of
speech, while we are engaged in conversation.
SECT. XXIV.
OF MUSCULAR MOTION. 
§ 299.
THE immediate organs of by far the
greater number of the motions of our bodies, are
the muscles, which constitute the principal portion
and bulk of what are called partes similares.
§ 300.
The muscles are, however, distinguished, in a
particular manner, from the rest of the similar
parts, by a two-fold characteristic; one depending
on 

208 OF MUSCULAR MOTION.
on their texture; and the other of a very singular
nature, derived from their vital energy.
§ 3O1.
Their texture is fleshy, composed of a peculiar
set of fibres, of a very pale red colour: they are
so joined together, that every muscle consists, in
the first place, of fibrous cords, these cords again,
of smaller bundles of fibres, which bundles, by a
still further progressive division, may be finally
separated and resolved into fleshy fibres and fibrils
of inconceivable minuteness.
§ 302.
Each muscle is inclosed in a cellular sheath or
covering, which, passing into the very substance
of the muscle, appears to be interwoven through-
out the whole of its volume, and thus forms par-
titions, first between the larger lacerti, then be-
tween the smaller fasciculi or bundles, and lastly,
between the fibres and more minute fibrils them-
selves.
§ 303.
Besides this cellular expansion, the whole tex-
ture of the muscles is also interspersed with an
infinitude of blood-vessels and nervous filaments;
of these, the latter appear to deliquate into an
inscrutable pulp, and to be thus very intimately
2 blended 
 

209 OF MUSCULAR MOTION. 
blended along with the muscular fibres; but the
former are so extensively and minutely interwoven
among those very tender fibres, as to paint the
whole of the fleshy parts with that beautiful crim-
son dye, by which they are uniformly characterised.
When these are thoroughly washed, they are
again restored to their native colour, which, as
already observed (§ 301.), is somewhat pale.
§ 304.
Finally, a circumstance common to most of the
muscles is, that they terminate in tendons-parts,
which, though likewise of a fibrous texture, are
notwithstanding so extremely different, with respect
to colour, structure, elasticity, &c. that their entire
disagreement from both the preceding kinds of
fibres, is very easily ascertained and demonstrated.
Hence, therefore, we are enabled successfully to
refute the opinion of those physiologists, who have
erroneously supposed, that the tendinous, are no-
thing more than mere continuations of the muscu-
lar fibres. To the adoption of this opinion, they
have been inadvertently led by attending to the
following phenomenon, observable in the muscles
of infants; namely, if we compare the muscular
parts, of these tender subjects, with those of adults,
we will find the proportion of flesh, to that of
tendon, greater in the former than in the latter.
VOL. I. O § 305

210 OF MUSCULAR MOTION.
§ 305.
The other exclusive characteristic of muscles,
which we have mentioned (§ 300.) is, the irrita-
bility of Haller. Although we endeavoured, on
a former occasion, to give a general view of this
vital energy, and to ascertain the difference be-
tween it and contractility, (§ 44.), yet it may not
be improper, at present, to pursue the inquiry a
little further.
§ 306.
This irritability, otherwise called vis muscularis,
vis insita, or vis propria, is indeed common to
all the muscular parts of our bodies, but does not
reside in all of them in the same degree, some parts
being observed to possess a much higher propor-
tion of it than others.
The principal seat of this energy, where it most
plentifully abounds, is the hollow muscles, sub-
servient to the vital and natural functions: of
these muscles, the heart, as was observed formerly
(§ 119.), possesses the highest degree of the cha-
racteristic now under consideration: of this last
mentioned organ, the internal surface, in parti-
cular, is endowed with the most exalted degree of
life, and is by far the most tenacious of irrita-
bility.
Next 

211 OF MUSCULAR MOTION. 
Next to the heart, in point of this prerogative,
is the intestinal canal, more especially that portion
of it which constitutes what are called the small
intestines: in warm-blooded animals, this part of
the tube sometimes contracts on being irritated,
even after the heart itself has become incapable of
motion.
Next in degree is the stomach,—next, the uri-
nary bladder, &c.
Among the remaining muscles of the system,
irritability resides, again, in a very striking degree,
in those actively concerned in the function of
respiration, as the diaphragm, the intercostals,
and the triangularis sterni.
Next in order to these are the various other
muscles of the body.
The arteries doubtless possess irritability, though
in a degree far inferior to what exists in the parts
just mentioned (§ 123.)
This vital energy resides also in the trunks of
veins contained in the thorax, (§ 84.)
In a degree still lower, does it exist, in the other
parts of the sanguiferous veins, if, indeed, those
O2 parts 


212 OF MUSCULAR MOTION.
parts can be said to possess any genuine irritability
at all (§ 128.)
§ 307.
Haller himself, that illustrious defender of the
doctrine now under consideration, appears to me
to have, without sufficient foundation, attributed
irritability to certain parts of the body, which are
found, indeed, on experiment, to be endowed
with contractility (§ 50 seq.), but in which I have
never been able to discover any indubitable testi-
monies of genuine irritability.
Among these parts may be reckoned the lacteal
veins, the small glands, the gall-bladder, the uterus,
the dartos covering, and the male penis.
On no better foundation, in my opinion, is irri-
tability attributed, by others, to the iris, to the
external surface of the lungs, &c. in all which
parts (if, indeed, I be capable of judging rightly),
there exists no more of this vital energy, than
there does in the common cellular membrane, and
parts composed of it, such, for instance, as the
common integuments, the meninges, the pleura,
the peritoneum, the periosteum, the medullary
membrane, the tendons, the aponeuroses, &c.;
or than there does in those viscera composed of
genuine parenchyma, (§ 27.), such as the liver,
the 


213 OF MUSCULAR MOTION. 
the spleen, the kidneys, the secundines, the brain,
with the rest of the nervous system, &c. all which
parts, as they are throughout, completely destitute
of muscular fibres, so are they likewise destitute of
irritability, which resides in muscular fibres alone.
§ 308.
As we have, thus, on the one hand, seen
muscular irritability now and then confounded
with cellular contractility, so on the other, certain
celebrated characters have lately been desirous of
ascertaining and establishing an identity between
irritability and the vis nervea.
For although we can neither deny the power-
ful influence of the nerves on muscular motion, (of
which we will speak a few words presently), nor
exhibit the smallest fibril of muscular flesh, per-
fectly destitute of the pulp of evanescent nerves,
yet these circumstances are not sufficiently mo-
mentuous to compel us to a dereliction of the
opinion, that irritability is, in its own nature, as
widely and essentially different from the vis nervea
as it is from contractility. On the one hand,
this energy is wanting in all parts not muscular,
although they be supplied with the utmost profu-
sion of nerves, as the skin, all the nervous viscera,
&c; whereas, on the other, we are not able to
produce any portion of true muscular flesh, where
O3 the 

214 OF MUSCULAR MOTION.
the genuine and obvious phenomena of irritability
do not exhibit themselves. From a close and
impartial consideration of the foregoing argu-
ments, besides a great number of others which
might be advanced, it appears more consonant to
reason and found induction, to attribute the
singular phenomena of irritability to the equally
singular texture of muscular fibres, than to refer
them to the nerves, which, in so many other parts
of the body, are as minutely distributed as they are
through the muscles, and yet do not generate and
exhibit, in those parts, the faintest shadow of real
irritability. I say nothing of the weighty argu-
ments which might be drawn from the following
well-founded position, viz. that no steady propor-
tional relation is observed to exist, between the
degree of irritability in any part of the body, and
the quantity of nerves with which it is supplied.
§ 309.
With respect to the extreme terminations of
the nerves, which are well known to exert an
influence over the muscles, the following appears
to be the most rational conclusion, viz. that they may
be considered as remote or exciting causes of mus-
cular motion, but should not be confounded with
the proximate or efficient cause, which is indeed
irritability alone, and that residing exclusively in
the muscular fibres.
The 


215 OF MUSCULAR MOTION.
The passions of the mind, for example, act on
the sensorium, this again re-acts on the nerves of
the heart, in such a manner, as to excite its irrita-
bility, and thus produce palpitations and other
irregular motions of this organ.
The will acts on the sensorium, this re-acts
again on the nerves of the arm, these nerves in
like manner operate immediately as remote causes
in exciting muscular motion, which, notwith-
standing, depends ultimately for its existence on
irritability itself.
§ 310.
This distinction, of the two kinds of causes
which concur in the production of muscular
motion, is indeed fully authorised and sanctioned
by actual experiments: from a variety of these it
appears, that certain parts of the animal system
have been oftentimes rendered paralytic, by cutting,
or inclosing in ligatures, the nerves leading to them,
while they have, notwithstanding, still continued to
retain their irritability for a long time afterwards.
§ 311.
In what degree the blood, with which the
muscles are very abundantly supplied, contributes
to their action, is not yet clearly and satisfactorily
ascertained.
O4 It 

216 OF MUSCULAR MOTION.
It appears, however, from an experiment of
Steno, that a paralysis of the lower extremities
may be generally produced, by passing a ligature
round the aorta in its descent behind the abdo-
minal cavity.
§ 312.
Besides these common inherent energies of the
muscles, which have hitherto been the subjects of
our consideration, they possess also certain specific
and adventitious peculiarities, arising from varieties
in their figures, situations, &c. by these peculia-
rities they are adapted, and rendered completely
adequate, to the nice performance of their several
functions.
§ 313.
From the contemplation of this circumstance,
muscles are usually divided into hollow and solid:
the former of these, as we have already seen, not
being in immediate subjection to the command of
the will, are particularly destined to the perfor-
mance of the vital and natural functions, and
cannot, therefore, be further treated of in this
place, where we are considering what are called
voluntary muscles, which are more especially sub-
servient to that order denominated the animal
functions.
§ 314. 

217 OF MUSCULAR MOTION. 
§ 314.
Between these last-mentioned muscles them-
selves, there occur again very stiking diversities.
For to say nothing of the varieties in their relative
magnitudes, they differ extremely from each other
in the disposition of their lacerti and fasciculi, in
the direction of their fibres, but more especially
in the habit and proportional relation of their
fleshy and tendinous parts, and, finally in their
courses, their insertions, &c.
§ 315.
Nevertheless, in by far the greater part of the
fusiform or tapering muscles, their figures are
more or less oblong, so that their fleshy bellies
terminate at each end in tendinous cords. These
cords, which are inert and perfectly destitute of
irritability, being attached to, and inserted in,
bones, serve the necessary purpose of moving
them after the manner of levers.
§ 316.
As there are, however, a few muscles in the
body entirely destitute of tendons, such as the
latissimus colli; so there are, in like manner, a few
not attached to bones, namely, the muscle last
mentioned, the cremaster muscle, as it is generally
called, the azygos uvulæ, and most of those which
move the ball of the eye.
§ 317. 

218 OF MUSCULAR MOTION.
§ 3l7.
By the co-operation and combined aid of all
those energies, (as well the common, § 305, as
the proper, § 312), with which the muscles are
furnished these instruments of motion are fitted
and completely qualified for the performance of
their several actions, which may, in like manner,
be also divided into common and proper.
§ 318.
During their common action, which arises
immediately from irritability, and occurs in all
muscles, their fleshy portions become shorter,
more rigid, and, for the most part, unevenly and
somewhat angular. It also appears from the
celebrated experiment of Glisson, that they suffer
at the same time a slight diminution in point of
magnitude.
We are indeed prevented from joining Jo.
and Dan. Bernouille, and other mathematical
physicians, in an attempt to reduce the measure
of this diminution to common calculation, first, by
the immense difference in this respect, which is
observable between the hollow and solid muscles,
and secondly, by the diversity which also occurs,
on the same point, between these latter muscles
themselves;—not to mention various other diffi-
culties, which obstruct the road to success.
§ 319. 

219 OF MUSCULAR MOTION. 
§ 319.
The proper or specific actions of the muscles,
(§ 317.), correspond precisely to their specific
energies; from whence it naturally and sponta-
neously follows, that these actions are marked
with such an infinitude of varieties, as to render it
literally impossible to reduce them to any general
laws, or to arrange them under any well-defined
orders and genera.
With regard to the general principle, commonly
taught and adopted on this subject, viz. that every
muscle while in action, draws the more moveable
part to which it is attached, towards that which is
more permanent, it ought to be considered, (as has
been very justly observed by the sagacious Winslow)
in a relative point of view, and is indeed subject
to a variety of limitations. Thus, for example,
the two parts to which a muscle is attached, may 
be rendered, each more moveable than the other,
in alternate vicissitudes, accordingly as the one or
the other is fixed and rendered stationary, by the
joint action of other co-operating muscles.
As to the action of the flexor muscles, it ought
to be estimated on contrary principles, and a dif-
ferent opinion formed respecting it. Although
these muscles, for the most part, predominate so
much over their antagonists, the extensors, that
when

220 OF MUSCULAR MOTION.
when the body is in a state of perfect quietude
and rest, the arms, fingers, &c. are under a gentle
degree of flexion, yet these parts do not appear to
be drawn into this state and position by any actual
force, but rather in consequence of a voluntary
relaxation of their extensor muscles, by means of
which, those muscles, subservient to the flexion of
the parts, are left at liberty to act without oppo-
siton or resistance.
§ 320.
To all the foregoing considerations, it appears
proper to add, in the last place, that each muscle
possesses a peculiar amd specific mechanism, by
means of which it is adapted, in the most complete
manner, to the performance of the various motions
of its immediate destination.
Besides the peculiar advantages which the
muscles severally derive from their determinate
figures, their actions are also promoted by a variety
of other concomitant aids, such, for instance, as the
annular ligaments by which they are surrounded;
the fat, in which a great number of them are
imbedded; the lymphatic dew with which they
all abound; and, what ought to have been men-
tioned in the very first instance, the conformation
of the skeleton itself, especially as far as the same
relates to the structure of the apophyses, and the
articulation 


221 OF MUSCULAR MOTION. 
articulation of the joints: under the same head of
auxiliaries to the muscles, may be also arranged
certain entire bones, as the patellæ, and ossa
sesimoidea, of similar structures and uses, which
nature appears to have very wisely adapted and
destined to facilitate the motions of particular
muscles.
§ 321.
By these diversified and numerous aids, has
nature made compensation for, or at least very
considerably diminished, that inevitable loss of
power, which necessarily arises from the confor-
mation and stature of the whole body. The
acuteness of the angles formed by the insertions
of a great many muscles, and the vicinity of these
insertions to the centres of motion, may be brought
forward as incontrovertible testimonies in favour
of such a loss of power, which would not have
been sustained, had the tendinous cords been in-
serted at greater distances from the centres of
motion, or in such directions, as to have formed
more obtuse angles.
§ 322.
To our bodies, thus furnished with about four
hundred and fifty muscles, together with a few
occasional supernumeraries, (arising from sexual
and individual varieties), two advantages of the
utmost magnitude and importance are very obvi-
ously


222 OF MUSCULAR MOTION.
ously derived. First, in consequence of this beau-
tiful and complicated system of organs, not only
our individual members, but also our whole bo-
dies, are rendered capable of the most astonishing
agility, in point of motion; and secondly, from
the same source, we derive such remarkable de-
grees of strength, as qualify us to bear, without
injury, the most arduous species of labour and
fatigue. These two momentous advantages de-
pend, indeed, in part, on a perfect state of the
muscles, to which, no less than to a perfect state
of the bones, we arrive by degrees, as youth
advances towards maturity; but they are also, in
part acquired by a frequency of use and exercise.
The powerful influence which those two latter
circumstances possess and exert over the muscles,
in strengthening them and rendering them capable
of the utmost agility of motion, is strikingly de-
monstrated by numerous examples of rope-walkers,
of dancers, of runners, of wrestlers, of boxers,
and of those robust barbarians, who constituted
the glory and boast of former ages.
SECT.

223 OF SLEEP. 
SECT. XXV.
OF SLEEP.
§ 323.
THOSE two species of nervous action,
(the history of which we have now completed)
that have for their ultimate ends sensation and
motion, are so reduced and debilitated by the
diversified exercises of the day, that repose
by night becomes absolutely necessary, for the
purpose of refreshing their declining vigour
and energy, which sleep alone, the image, or sem-
blance of gelid death, is able completely to restore.
§ 324.
Sleep is a function perfectly periodical, which
suspends, as it were, for a time, all intercourse
and communication between the mind and body.
The various phenomena of this function, some of
which shall be immediately enumerated, appear to
declare, with no small force of evidence, in favour
of the existence of a nervous fluid.
§325.
Besides a variety of other circumstances, we
may here enumerate as precursors and harbingers
of

224 OF SLEEP.
of sleep, a sluggishness and gradually increasing
dullness of the external senses, together with a
relaxation of most of the voluntary muscles,
especially such as are of considerable length. To
these may be added a congestion of the venous
blood in, and near, the heart, and an effort to
remove the uneasiness thence arising, by the aid
of yawning. Finally, the only additional pre-
cursor to be mentioned at present, which appears
to constitute the very isthmus, as it were, between
the waking and sleeping states, and the immediate
transition of the former into the latter, is a pecu-
liar species of transient delirium.
§ 326.
The following are what constitute the principal
phenomena of sleep, when that state has actually
occurred: the animal functions are wholly sus-
pended from action, while almost all the others are
at the same time performed in a more sluggish and
torpid manner; thus, in subjects buried in sleep,
all other circumstances being alike, the pulse is
slower, and the heat of the body somewhat
diminished; perspiration is also less plentiful;
digestion less powerful; and (if the occasional
discharge of the semen masculinum be excepted)
all the excretions are suppressed, &c.
I § 327.

225 OF SLEEP.
§ 327.
The remote causes which induce sleep are very
plain and obvious. For to say nothing of narcotic
substances themselves, we may consider as very
energetic causes in the production of this state, all
waste of the animal powers by means of preceding
fatigue, by watching, &c. To these we may sub-
join the influence of custom, together with dark-
ness, silence, rest, &c. which appear indeed to
derive their somniferous powers from the same
source; we may also further add, gentle, uniform,
and constant impressions acting on any of the
senses, such, for instance, as the soft murmurings
of the rill, or the appearance of a harvest field,
agitated and thrown into wavy undulations, by the
mild fannings of the western breeze, &c. Under
the same head of remote causes we may also con-
sider, full meals, and intense cold acting on the
body, together with a variety of other circum-
stances, tending to derive the blood from the
encephalon, as pediluvia, clysters, and profuse
hemorrhages, &e.
§ 327.
Those remote causes which we have mentioned
in the latter part of the preceding paragraph, are,
of themselves, sufficient to conduct us to the proxi-
mate cause, which appears, from the best evidence
VOL. I. P that 

226 OF SLEEP.
that can be collected on the subject, to consist in
a diminution of the column of blood that goes to
supply the encephalon.
That this is indeed the proximate cause of sleep,
is powerfully illustrated and confirmed, by a very
singular and striking phenomenon, which I had
once an opportunity of observing in a living
human subject, whose case has been already men-
tioned on another occasion. As often, and as
long, as this person indulged himself in sleep, his
brain subsided and continued in a state of consi-
derable collapse, but during his waking hours
throughout the day, this organ became again
turgid and distended in consequence of a more
copious afflux of blood.
As an additional argument in support of the
same cause, we may observe, that morbid watch-
fulness, on the other hand, usually arises from
congestions of blood in the region of the brain.
§ 329.
The quantity of sleep necessary, depends in a
great measure on varieties in age, habit of body,
temperament, &c. The general result, however,
of all the existing evidences on this subject,
appears to be, that a longer indulgence in sleep is
either a concomitant of imbecility (as is the case
in 

227 OF SLEEP. 
in tender infants. and subjects far advanced in
years), or a very exuberant source of fatuity and
dullness.
§ 330.
We rise from sleep with renovated powers, and
our return into the living, and completely waking
state, is accompanied with symptoms and pheno-
mena very similar to those which attended our
transition from this state into that of sleep: we are
attacked, for instance, by a yawning, accom-
panied for the most part with more or less of a
stretching, we are also affected by a certain dull-
ness, and torpidity of the senses, &c.
§ 331.
The causes which rouse into wakefulness, ap-
pear to correspond exactly with those productive
of sleep.
The proximate cause will be the return of a
more copious column of blood into the ence-
phalon.
The remote causes, besides the power of
custom, which is confessedly very great, consist of
an immense variety of stimuli, that may be divided
into external and internal. The external are
calculated to excite the numbering senses, while
P2 the 

228 OF SLEEP.
the internal act either immediately on the body
itself, as the distension of the urinary bladder; or
impress the nervous system through the medium
of the imagination, the mode in which dreams
operate.
§ 332.
Dreams are light sportings of the imagination,
in which it recalls the images of things formerly
perceived, and appears to exercise and busy itself
in arranging and combining them into the most
fantastical representations.
I have never been able to discover the slightest
vestige of this faculty in new-born infants pre-
viously to the third month after birth.
There are also various examples of adults who
explicitly declare, that they have no knowledge
of dreams, having never been troubled by them.
Those visions of the night are, for the most
part, indeed, confused and irregular; but they
are, notwithstanding, sometimes marked with
astonishing vestiges of reason.
The influence of stimuli acting on the body is
truly great in the production of dreams: thus the
stimulus of the male semen gives rise to lustful
2 ideas; 

229 OF SLEEP.
ideas; the stimulus of an excessive plethora calls up
images of a frightful and terrifying nature, &c. We
have even received a well confirmed account of a
man, to whom, while asleep, his friends could sug-
gest whatever visions they pleased, by communi-
cating to him the subject and matter of the dream
in a soft and gentle tone of voice. This appears
however, to belong rather to a preternatural state,
consisting of somnolency and wakefulness, of
which that truly morbid affection of the somnam-
bulantes, or those who walk in their sleep,
constitutes also another variety. 
It is necessary previously to the final conclusion
of this subject to observe, that Locke and others
have thought proper to consider all dreams as
belonging to this mixed or compound state.
END OF THE FIRST VOLUME. 



Elements of Phsiyology; 
BY
JO. FRED. BLUMENBACH, M.D.
PROFESSOR OF MEDICINE IN ORDINARY AT GOETTINGEN,
MEMBER OF THE ROYAL SOCIETY OF SCIENCES AT
GOETTINGEN, AND OF SEVERAL OTHER SOCIETIES IN
DIFFERENT PARTS OF EUROPE.
Translated from the Original Latin,
AND
INTERSPERSED WITH OCCASIONAL NOTES.
BY CHARLES CALDWELL.
TO WHICH IS SUBJOINED, BY THE TRANSLATOR,
An APPENDIX,
EXHIBITING A BRIEF AND COMPENDIOUS VIEW
OF THE EXISTING DISCOVERIES
Relative to the Subject of
ANIMAL ELECTRICITY.
VOLUME II.
PHILADELPHIA,
PRINTED BY THOMAS DOBSON,
AT THE STONE-HOUSE, N° 41, SOUTH SECOND-STREET.
M.DCC.XCV. 



ELEMENTS
OF
PHYSIOLOGY.
SECTION XXVI.
OF FOOD, AND THE APPETITE FOR IT.
§ 332.
As the waste of the animal powers is
again restored by sleep, so in like manner the in-
cessant loss of the natural powers, and even of the
very elementary parts of the body, is repaired by
fresh and repeated supplies of food.
§ 333.
To the acquisition and use of this food we are
forcibly led by the frequent and irresistable calls
of nature. These calls, though widely different
from each other in their natures, tend notwith-
standing to the final accomplishment of the same
end: they consist, on one hand, of the insupport-
VOL. II. A able 

2 OF FOOD AND APPETITE.
able torments of hunger and thirst; and on the
other, of the very pleasing, but no less powerful,
allurements of appetite.
§ 334.
The stimulus of hunger, some physiologists have
sought for in the mutual friction between the rugæ
of the stomach when empty; others in that which
appears, indeed, to be of primary importance in
giving birth to this potent sensation, namely, not
only in a more copious secretion and afflux of the
humours discharged into the first passages, more
especially of the saliva, the pancreatic juice, and
the bile, but also in a certain degree of morbid
acrimony, with which these same humours are apt
to be contaminated, unless such a state be guarded
against by regular supplies of nourishment.
§ 335.
Thirst is a distressing sensation, arising princi-
pally from a very troublesome dryness of the fau-
ces and esophagus; and also from a peculiar im-
pression produced by taking in acrid, but more
especially saline, substances.
§ 336.
With respect to the absolute necessity of satisfy-
ing and removing these stimuli, no fixed and posi-
tive rule can with propriety be laid down, as such
necessity 
 

3 OF FOOD AND APPETITE. 
necessity is doubtless rendered more or less urgent
by varieties in age, habit of body, and more espe-
cially by the power of custom. From a general
consideration of this subject, however, the result
appears to be, that an adult and healthy person,
who is under no undue impressions or influence,
(in whom, for instance, those assuasive calls of na-
ture are neither silenced by the louder ravings of
enthusiastic fanaticism, nor by other preternatural
causes) cannot refrain from the use of food, for
even one whole day, without a very great prostra-
tion of strength; and can seldom fast for more than
eight days without incurring the utmost hazard of
life.
§ 337.
With regard to drink, although a desire for
this appears to urge with the greater vehemence
and intensity of the two, it is, notwithstanding,
much less necessary to life and health than the ar-
ticle of food. This we infer, with apparently
strict propriety and truth, not only from numerous
species of warm-blooded animals, as mice, quails,
&c. that are never impelled by necessity to the use
of drink, but also from actual examples of certain
individuals of the human race, who have conti-
nued, through a long series of time, in the enjoy-
ment of life, health, and spirits, without recourse
to the use of drinks of any kind.
A2 § 338.


4 OF FOOD AND APPETITE.
§ 338.
As to food, controversies have existed respecting
the kind most proper to satisfy the internal calls
of our nature: whether, for example, the struc-
ture and constitution of the human body corres-
pond most perfectly with food taken from the ani-
mal, or with that derived from the vegetable,
kingdom; and which of these two kinds of sub-
stances nature, therefore, designed to constitute
the aliment of man?
§ 339.
That man is by nature an herbivorous animal,
Rousseau attempted, with a great degree of acute-
ness, to prove, not only by arguments taken from
the figure of his teeth, and the length of his in-
testines, but by the further consideration, that wo-
man is naturally uniparous, and furnished with
two mammæ, &c.; to all which might be added,
actual examples of rumination having been per-
formed by human subjects, a process well known
to belong exclusively to herbivorous animals.
Those, on the contrary, who, with Helvetius,
consider man as a carnivorous animal, attempt to
support their opinion by the shortness of his intes-
tinum cæcum, and other arguments of a similar
nature.
§ 340. 

5 OF FOOD AND APPETITE. 
§ 340.
But from more accurate observation, and a
more minute investigation of the subject, it ap-
pears, that nature did not intend to restrict man
to the exclusive use of either the one or the other
of those kinds of aliment, but more indulgently
destined him to a free participation of both. That
this is indeed the kind destination of man with re-
spect to the nature of his food, we very naturally
infer from his teeth, especially the molares, and the
conformation of his intestines, briefly mentioned
above, possessing a middle state between the same
parts, as they exist in carnivorous and in herbivo-
rous animals. This prerogative of man is, how-
ever, still more forcibly demonstrated, by the na-
ture of the articulation which connects the con-
dyles of the lower jaw to the ossa temporum in hu-
man subjects.
§ 341.
If the observations be true (and they surely
cannot be doubted) which we stated on a former
occasion, respecting the high privilege of man, in
being by far better calculated than other animals
for traversing an extensive range of climate on
the globe we inhabit, it from thence spontane-
ously follows, that he would have been indeed
very illy accommodated, in being solely restricted
either to the one or the other of the above kinds
A3 of

6 OF FOOD AND APPETITE.
of food: for as some regions of the globe afford
animal, and others vegetable food alone, the ob-
vious and unhappy result of such an exclusive re-
striction would have been, that man, though cal-
culated and destined to reside in all latitudes of
the earth, must, notwithstanding, in some of them,
be denied the use of such aliments as nature had
rendered essentially necessary to the continuation
of his existence.
§ 342.
Of all animals, with which we are in any mea-
sure acquainted, man may, with the strictest pro-
priety and truth, be said to be omnivorous. As
on the one hand he is calculated to banquet in
luxury, amidst the most profuse variety of delica-
cies that art can prepare from the immense re-
sources of the animal and vegetable kingdoms,
so, on the contrary, he is able to retain his health
and vigour when subsisting on the most simple and
frugal fare.
Thus, to produce only a very few examples, a
great many men even at the present day subsist
solely on a vegetable diet, such as potatoes, ches-
nuts, dates, &c. which constituted also the food of
the first progenitors of the human race: for it ap-
pears highly probable, that those simple and hardy
sons of nature, supported life first by the fruits and
roots 

7 OF FOOD AND APPETITE. 
roots of plants, and afterwards, by the more sub-
stantial and durable fare of grains and pulse.
Some of the Moorish tribes in Africa live almost
entirely on the gum senegal.
The inhabitants of Kamschatka and of a great
many other maritime situations subsist on fish.
In Europe itself, the Morlachi are supported al-
most entirely on a diet of flesh.
Some nations of Barbarians subsist even on raw
flesh, a circumstance which is undoubtedly true,
with respect to the Samoids, the Esquimaux, and
certain tribes of people inhabiting South America.
Neither are the liquids made use of as drinks,
in certain nations, less singular and striking.
Thus the inhabitants of several islands, which
lie between the tropics, more especially those situ-
ated in the Pacific Ocean, are entirely destitute of
sweet and pleasant water, and therefore, as a sub-
stitute for this fluid, use the delicious juice of the
lactescent cocoa.
Others again drink the waters of the briny
ocean;—from all which facts and circumstances,
A4 taken

8 OF MASTICATION
taken collectively, together with an infinitude of
others that might be adduced, we need not hesitate
a moment to pronounce, that man is literally an
omnivorous animal.
SECT. XXVII.
OF MASTICATION AND DEGLUTITION.
§ 343.
FOR the purpose of masticating the
more solid species of food, both our under, and
upper jaws, are armed with three different kinds
of teeth.
These are first, the incisores, which, in most
men, are chisel-formed, and well calculated to bite
off morsels of food.
Secondly, the canini, strong, conical and com-
pletely adapted for breaking substances of greater
firmness.
And lastly, the molares, of different sizes, exqui-
sitely fitted for the process of grinding.
§ 344. 

9 AND DEGLUTITION.
§ 344.
The mandible or lower jaw is connected to the
other parts of the head, by means of a very singu-
lar variety of articulation, which appears to be of
a middle nature between arthroida and ganglimus.
Being furnished with a pair of double concave car-
tilages, it thus unites, to a sufficient degree of
strength and firmness, a capacity of being easily
and very considerably moved in all directions.
The under jaw is drawn back, in opening the
mouth, chiefly by means of the musculus biventer,
but in part also by the geniohyoidei and the my-
lohyoidei.
It is brought back again, when we attempt to
cut any thing through with the dentes incisores,
and pressed with astonishing force against the
opposite jaw, during our efforts to crush any
hard substances, by the masseter and temporal
muscles.
It is moved laterally in chewing, by the action
of the internal and external pterygoid muscles;
the latter of which have also the power of moving
it in a forward direction.
§ 345.

10 OF MASTICATION
§ 345.
Substances taken into the mouth for the pur-
pose of being chewed, are retained, placed in a
proper situation, and thus effectually subjected to
the action of the teeth, by means of the musculus
buccinator, and the tongue, an organ of extreme
flexibility, and very capable of changing its form
(§ 233).
§ 346.
During the act of manducation we emulge, as
it were, a certain quantity of saliva, which is an
aqueous liquid, of a nature somewhat saponace-
ous; it contains a small quantity of earthy matter,
(which gives origin to tartarous incrustations of
the teeth, and to small sublingual calculi); this
fluid, from being in perpetual contact with the
tongue, makes no sensible impressions of taste on
that organ, although it contains a small quantity
of microcosmic salt; it possesses antiseptic and re-
solvent properties, and has also a power of spee-
dily exciting the process of fermentation in vege-
table substances, especially in those of the farina-
ceous kind.
§ 347.
The sources from whence this fluid is derived
are, small conglomerate glands, of three several
orders, 

11 AND DEGLUTITION.
orders, the lateral and internal, of which are situ-
ated beneath the lower jaw.
The most considerable of these glands, called
parotids, (remarkable, on account of being ex-
tremely subject to metastases), excrete their saliva
through the Stenonian duct, just behind the middle
molar tooth of the upper jaw.
The saliva furnished by the submaxillary glands,
is discharged through the duct of Wharton.
That derived from the sublingual glands, which
are the least of all, flows through the numerous
ducts of Rivinus.
§ 348.
The excretion of saliva, (of which, in confor-
mity to the opinion of Nuck, about a pint is com-
monly supposed to be secreted in the space of
twelve hours), is considerably encreased both by
the application of any stimulating substance, and
also by mechanical pressure, the latter of which
appears to act merely by emulging the containing
parts.
Thus, whatever hard substances we chew, be-
come perfectly moistened and macerated, as it
were, by a copious afflux of saliva produced in
conse-

12 OF MASTICATION
consequence of the pressure, to which the parotids
are particularly exposed from, being situated so
near to the articulation of the lower jaw.
With regard to the operation of stimuli on the
secretion of this fluid, it is necessary farther to ob-
serve, that when acrid substances are taken into
the mouth, a plentiful afflux of saliva is immedi-
ately produced, which has the effect of diluting
and thus effectually counteracting the irritating
acrimony: an increase of the same fluid is also oc-
casionally produced by the stimulus of the imagi-
nation; to this cause must we refer that afflux of
saliva, which so frequently accompanies a strong
appetite for food.
§ 349.
With the saliva are blended a fine aqueous,
dew-like fluid, which transudes from the soft parts
of the mouth, and also a mucus, secreted by small
glands, situated in the lips and cheeks: it is a
portion of this mucus by which the tongue is lu-
bricated.
§ 350.
The morsel during mastication, being thorough-
ly moistened by this mixture of saliva and other
animal juices, is thus, not only converted by de-
grees into a soft pulpy bolus, more fit for the pur-
pose 

13 AND DEGLUTITION. 
pose of deglutition, but is likewise prepared, at
the same time, for further digestion and final assi-
milation.
§ 351.
The actual business of deglutition, although it
appears to be of a very compound nature, and is
indeed performed by the co-operation of a great
many different parts, may be considered as com-
mencing and proceeding in the following order;
viz. the tongue being first retracted towards its
basis, and becoming therefore somewhat turgid
and stiff, receives on its excavated dorsum or back,
the lubricated and moistened bolus, which is from
thence forced onwards into the fauces, where it
is received by the expanded infundibulum of the
pharynx, which appears, at the same time, to ad-
vance somewhat upwards; on the reception of the
food the infundibulum makes a singular and vio-
lent exertion, which may be supposed to proceed
from a species of vita propria; from this funnel-
like entrance, the bolus is again protruded on-
ward, by a threefold contraction of the pharynx,
into the œsophagus. All the above motions suc-
ceed each other with the utmost degree of rapidi-
ty, and are of extremely short continuance.
§ 352.
For the purposes of expanding this passage, and
rendering it at the same time steady and secure,
nature 

14 OF MASTICATION
nature has made the most ample provision by a
variety of auxiliary parts.
The motion of the tongue, in this momentous
business, is regulated and directed by the os hyo-
ideum.
To prevent any of the substances swallowed,
from passing, by mistake, either into the internal
nares, or into the eustachean tubes, the soft palate
is very wisely provided. This fleshy curtain, de-
pending equally from the arched roof to which it
is attached, is capable of being rendered tense by
the action of a peculiar set of muscles, and thus
the above passages may be completely closed.
The glottis is securely guarded by the tongue
itself, because at the very instant in which we at-
tempt to swallow, the larynx, being drawn up-
ward and forward, is in a certain degree concealed
beneath the retracted basis of the tongue, and is
so compressed by it, that the glottis, not only by
this constriction, but also by the additional security
of the epiglottis, is thus very effectually guarded
against the intrusive entrance of any heterogene-
ous substances.
§ 353.
Finally, the business of deglutition is greatly fa-
cilitated by means of a quantity of mucus, with
which 


15 AND DEGLUTITION. 
which the whole of the passage above described
is lubricated; and which, besides the lingual
glands already mentioned (§ 235), is chiefly fur-
nished by the numerous sinuses of the tonsils, and
by that infinitude of mucaginous cryptœ, so pro-
fusely bestowed on the larynx itself.
§ 354.
With respect to the œsophagus itself, through
which all substances swallowed must necessarily
pass, previously to their entrance into the stomach,
it is a fleshy canal, rather narrow in its diameter,
and exceedingly firm and strong, but at the same
timepliable, dilatable, and possessed of a high degree
of sensibility: it is composed of tunics or coats,
which, if we except the difference in their thick-
ness, bear no small resemblance to the coats of the
other portions of the alimentary canal.
Thus, the external covering is muscular, made
up of fibres running both longitudinally and in
transverse or circular directions.
The middle coat is nervous, ending on each side
in a very lax cellular membrane, by means of
which it is connected, as well to the preceding, as
to the subsequent tunic.
Lastly, 


16 OF DIGESTION.
Lastly, the internal coat is lined by mucus of an
exquisite degree of lubricity.
§ 355.
The following appears to be the mode in which
this canal performs its office; as soon as it has re-
ceived either a draught or bolus completely within
its parietes, the parts immediately above presently
contract themselves, thus forcing downwards the
substance to be swallowed; which, if it be a bo-
lus, can be protruded onward only by one uni-
form series of exertions in the surrounding tube,
till it has passed through the diaphragm, and been
finally received into the cavity of the stomach
itself.
SECT. XXVIII.
OF DIGESTION.
§ 356.
THE chamber, or immediate seat of di-
gestion, is the stomach, a viscus more uniformly
possessed than any other, by almost every indivi-
dual throughout the immense range of animated
nature: if, therefore, we estimate the dignity of
the several viscera from this circumstance alone,
the stomach is, doubtless, to be considered as an
I organ

17 OF DIGESTION.
organ surpassing all the others in utility and im-
portance to the animal economy.
§ 357.
The human stomach resembles a leathern pouch,
of very considerable dimensions, sufficient, for the
most part, in an adult, to contain three pints, or
more, of water, and furnished with two separate
orifices or mouths:
These are, first, a superior orifice, called car-
dia, which is formed in the place where the œso-
phagus, by a plaited and somewhat oblique aper-
ture, opens into the stomach itself, and points to-
wards the bottom of this viscus, or that extremity
which regards the left side of the body.
Secondly, an inferior one, which constitutes the
termination of the right, and less capacious end of
the stomach: this orifice is called pylorus, and de-
scends a short distance into the cavity of the ad-
joining duodenum.
§ 358.
The situation of the stomach, when empty, is
different from that of the same organ, when full:
thus, in the former state, it hangs loose and flaccid
in the abdominal cavity, in such a manner that its
greater curvature looks in a backward direction;
VOL. II B and 


18 OF DIGESTION.
and its pylorus, being turned somewhat upwards,
forms a plaited or twisted angle with the duode-
num, to which it is connected.
But in the latter state, when distended with food,
its greater curvature is again turned, and looks in
an anterior direction, so that the pylorus enters
now, by a more direct route, into the duodenum;
whereas the cardia, on the contrary, is so folded
and bent as to be completely closed.
§ 359.
The stomach is composed of four principal
coats, distinguished and separated by three others,
of an entirely cellular nature, which lie between
them.
The most external of these coverings is common
to the stomach, with all the rest (save a small por-
tion) of the alimentary canal, and is continued
over the omenta, which shall be spoken of here-
after.
Next to this, lies that cellulo-muscular coat, so
very striking in its nature and properties, on which
depend both the exquisite irritability of the sto-
mach (§ 306.), and also its peristaltic motion; the
latter of which shall be a subject of consideration
in another place. This coat is composed of dif-
ferent 


19 OF DIGESTION. 
ferent strata of muscular fibres, which are usually
divided into three orders, one longitudinal, and
two circular; the circular fibres are again divided
into those that are directly, and those that are ob-
liquely, circular. It must, however, be observed,
that so extremely variable and irregular are the fi-
bres of this coat, with regard to their direction
and distribution, as scarcely to admit of reduction
to, and arrangement under, any determinate and
general rules.
The third principal coat is called the nervous,
an appellation extremely improper, as it is compo-
sed wholly of condensed cellular membrane, be-
coming gradually more soft and lax on each side;
by which means it is connected externally to the
muscular, and internally to what we shall presently
call the villous, coat. It is, notwithstanding, so
firm and robust, that it may be aptly enough call-
ed the basis of the whole stomach.
Lastly, the internal coat, which has been very
improperly called villous, is exceedingly tender,
somewhat spongy, porous, and folded into a very
great number of rugæ or wrinkles, so that its area
is much more extensive than that of any of the
other coats which we have just described: it every
where exhibits cells of the utmost minuteness, some-
B2 what 

20 OF DIGESTION.
what similar in appearance to those larger ones,
with which the reticulum of ruminating animals
is very beautifully and elegantly characterized.
The internal surface of this coat is lined with
mucus, apparently secreted by small mucaginous
cryptæ, some of which may be, indeed, readily
enough distinguished near to the pylorus, or lower
orifice of this organ.
§ 360.
The stomach is furnished with an astonishing
apparatus of nerves, whence its sensibility is so ex-
quisite, that it is capable of being very readily af-
fected by stimuli of almost every kind, whether
they be external, as cold &c. or internal as food,
and even by the inquiline humours themselves.
From the same source arises also that extensive,
and truly admirable consent, which exists between
this important viscus and most of the other func-
tions of the body; to which head belongs, in a
particular manner, the striking effects, produced
on the stomach, by all mental commotions, and
also, on the other hand, the very powerful influ-
ence of an entirely sound and healthy state of this
organ, on the cheerfulness and serenity of the
mind.
§ 561.


21 OF DIGESTION.
§ 361.
The number and functions of the blood vessels,
belonging to the stomach, are no less considerable
and striking, than those of the nerves. The small
arteries, (of which an infinitude of different or-
ders, are minutely interspersed throughout the cel-
lular coats of this organ), appear to constitute the
immediate sources of the gastric juice, a liquor
which flows in perpetual streamlets from the inter-
nal surface of the stomach.
§ 362.
This juice bears, on the whole, no small resem-
blance to saliva, except that, agreeably to the ex-
periments of the illustrious Spalanzani, its powers
are counter to those which promote fermentation.
As to the rest of its properties, it is saponaceous,
equally antiseptic with the saliva, and is indeed, a
very powerful menstruum, sufficient gradually to
dissolve milk after it has been gently coagulated in
the stomach.
§ 363.
The gastric juice appears to be the most power-
ful and active agent in the great business of diges-
tion. If the food be carefully masticated, and suf-
ficiently blended with the menstruum furnished by
the salivary glands, this fluid of the stomach com-
B3 pletely 

22 OF DIGESTION.
pletely dissolves, and finally converts it, into a
soft pultaceous chyme.
§ 364.
This momentous function is also further aided
and prompted, by a variety of accessory and assis-
tant powers: of these the most considerable is the
peristaltic motion, by means of which the food,
now reduced to a pulpy consistence, is thoroughly
agitated, and kept perpetually in a state of wavy
commotion. Although the force of the peristaltic
motion fall far short of the chimerical calculations,
formerly made on this subject, by mathematical
physicians, and although it be not itself the sole
cause of digestion, it is, notwithstanding, of the
utmost efficacy and influence in this important
process.
§ 365.
Among the auxiliary powers, of this kind, may
be also reckoned another species of motion, which
the pressure of the surrounding parietes of the ab-
domen, communicates to the stomach: to these
we may still farther subjoin, the extreme warmth
of the situation in which this viscus is placed; so
very powerful was this fotus or bath, formerly
esteemed, in consequence of the abundant quan-
tity of blood contained in the neighbouring vessels
and 
 

23 OF DIGESTION. 
and viscera, that instead of the term digestion,
that of coction, was used by the greater part of
physiologists.
§ 366.
To determine, with precision, the period of time
requisite for the conversion of our aliment into
chyme by the joint co-operation of the foregoing
powers (§ 361.), will appear almost impossible to
any one, who may consider the great variety of
circumstances, on which such conversion must de-
pend: these circumstances are, the quality and
quantity of the food taken in, the different degrees
of force in the digestive powers, the greater or
less attention and care bestowed on the prepara-
tion of the food for digestion, by previous masti-
cation, &c
For in a healthy subject, the unimpaired sto-
mach does not discharge such alimentary matters
as have been taken in, previously to the conver-
sion of their digestible parts into a perfect pulp.
From whence it is evident, that different periods
of time are requisite, for the complete digestion of
different kinds of food. If, however, it be allow-
able to form any general conclusion on this subject,
it would appear, that from the third, to the sixth
hour, after the use of aliment, the stomach has,
for the most part, discharged through the pylorus,
B4 in 


24 OF DIGESTION.
in a very gradual manner, the whole of its pul-
taceous contents.
§ 367.
The pylorus is an annular rim, not formed,
(like the other rugæ on the internal surface of the
stomach), by the folding of the villous coat alone,
but consisting, in part, also of a few fasciculi from
the subjacent nervous, and also of certain fibres
from the muscular, coat: all which parts are so
organized and arranged, as to constitute a coniform
termination to the stomach, that is extended into,
and embraced by, the duodenum, in the same
manner as the os uteri is received and embraced,
by the superior part of the vagina.
SECT. XXIX.
OF THE PANCREATIC JUICE.
§ 368.
Subsequent to the expulsion of
the chyme through the pylorus, that pulpy mass
must be subjected, in the duodenum (a short, but
remarkable portion of the intestinal tube), to new
and considerable changes, previously to the for-
mation

25 OF THE PANCREATIC JUICE. 
mation and final separation of complete, alimen-
tary chyle. These necessary changes are effected
in the chyme by the accession and admixture of
various kinds of inquiline humours, the most strik-
ing and important of which, are, the bile and the
pancreatic juice.
§ 369.
Of these two humours, we will speak in sepa-
rate sections. We proceed therefore, to consider
the liquor of the pancreas first, because it appears
to bear a very considerable resemblance, both in
its nature and uses, to those other two dissolvent
humours, of which we have already spoken, name-
ly, the saliva and the gastric fluid.
§ 370.
Athough it be indeed a matter of no small diffi-
culty, to procure the pancreatic liquor of a found
animal, in a pure and unadulterated state, yet the
obvious and unequivocal result of all the facts,
which the most attentive investigation has been
able to supply, with regard to its nature, is, that
it bears the strongest similitude to the saliva in all
its general properties. Were it not for the pur-
pose of showing how mischievous, and even de-
structive, the practice of medicine may become,
unless directed by found principles of physiology,
I should not think it necessary nor even proper, at
the 

26 OF THE PANCREATIC JUICE.
the present enlightened period, to mention the er-
roneous physiological hypotheses, entertained by
Franc. Sylvius, and his humble followers, Regn.
de Graef, Flor. Schuyl, and others, respecting
the visionary or supposed acidity of the pancreatic
liquor, especially as those opinions have been long
since very ably refuted by Pechlin, Swammerdam,
and Brunner, characters of the first celebrity in
the annals of medical science.
§ 371.
The sources from whence the lymph and saliva
are derived, bear no small resemblance to that
which constitutes the subject of our present consi-
deration, namely, the pancreas: this latter is by
far the largest of all the conglomerate glands of
the human body, and exhibits, in the whole of its
structure, a very striking similitude to the glands,
that give birth to the salivary fluid; with these
last mentioned bodies it also further agrees, in this
particular, that its excretory canals, arising from
radicles of the utmost minuteness, run together
and unite by degrees, till they constitute finally a
common duct, which has received its name from
Jo. G. Wirsung, who first discovered and de-
monstrated it in the human subject, in the year
1642.
This 

27 OF THE PANCREATIC JUICE. 
This duct passes through the coats of the duo-
denum, and by a constant stillicidium, weeps into
the cavity of that intestine, the fluid it had receiv-
ed from the gland to which it is appended.
§ 372.
Finally, the excretion of this fluid appears to be
promoted by the very same powers, which were
formerly said to be subservient to the excretion of
saliva, namely, pressure and stimulus.
By means oS the former, it is emulged chiefly
when the stomach is distended and rests immedi-
ately on the pancreas.
The substances that contribute most, by their
irritations, to excite a discharge of the pancreatic
fluid are, first, the chyme itself, as it passes through
the pylorus in a crude and unassimilated state; and
secondly, the bile, which is discharged through
the very same orifice with the liquor of the pan-
creas.
§ 373.
The use of this fluid is doubtless to dissolve the
chyme, more especially that part of it, which has
not been sufficiently digested in the stomach: by
its abundant afflux, it contributes to assimilate this
pulpy

28 OF THE BILE.
pulpy mass still more and more to the nature of
the inquiline humours, and thus finally mature it
for the further process of chylification.
SECT. XXX.
OF THE BILE * 
§ 374.
THE secretion of bile is the pecu-
liar destination of the liver, the largest and most
ponderous viscus in man. This superiority of size
is more especially observable, during the fœtal
* Doctor Maclurg, of Virginia, published in the year
1772, an experimental treatise on the formation, the nature
and the uses of the human bile, which has acquired for its
learned and ingenious author, no small degree of reputation
both at home and abroad. That this elaborate publication
possesses an uncommon share of merit, not even the avowed
enemies of the Doctor are themselves able to deny. The
author has shewn himself to be, at least, a very patient expe-
rimenter, and an extremely attentive observer. He appears
to have made himself perfectly master of the opinions of all
authors of celebrity and distinction, who had previously writ-
ten on the same subject. With regard to the literary merit of
the composition itself, it is doubtless entitled to the highest en-
comiums that even the most partial eulogist can bestow. The
order

29 OF THE BILE. 
state, in which, the younger the fœtus the greater
is the proportional magnitude of the liver, when
compared with that of the other viscera of the
order is inimitably lucid, the style is chaste, manly and ner-
vous in the highest degree, and as to closeness and propriety
of argumentative arrangement, not even the supercilious lo-
gician himself, can find room to suggest the shadow of an
amendment.
All human compositions are, however, like the sources
from whence they originate, in some measure faulty and im-
perfect. To this general maxim, humiliating as it may ap-
pear to the pride of the self-adoring philosopher, the treatise
of the illustrious Maclurg is by no means an exception. In
several of the Doctor's experiments there appears to be a
want of sufficient accuracy and definitude, in others a want
of object and design. Over these faults, however, consider-
able as they are in the works of an experimentalist, we feel
inclined to spread a kind mantle of palliation, when we re-
collect that our author experimented and wrote in the early
morn of scientific chemistry. Experimenters had not yet be-
come perfect adepts in their nice and momentous art; they
had not yet acquired sufficient circumspection and address to
obviate every source of fallacy, and to avail themselves of
every circumstance that might pave the way to satisfactory
and unequivocal results.
But another charge of a more weighty and important na-
ture, lies against our learned and ingenious author. He has
certainly built, on nothing more substantial than the flimsy
basis of deceptious analogy, some of the leading principles of
his favourite doctrine. Thus, for example, he supposes the
bile 


30 OF THE BILE.
body. The dignity and high importance of this
viscus in the animal economy may be fairly de-
duced, from the universality of its presence; thus
bile to be a fluid, the direct result of a putrefactive degene-
racy in a portion of the circulating volume of the blood.
His most plausible reasons in support of this opinion are, first,
that the parts, from whence the incipient radicles of the vena
portarum immediately originate, contain, and communicate
with, matter already in a semiputrescent state. And second-
ly, that the bile is most abundant in quantity and most active
with regard to its quality, at that season, and under those
circumstances, which are most favourable to the commence-
ment and progress of putrefaction in the living system, as
well as in all other physical bodies.
Plausible as those arguments may, on first view appear,
they are certainly, as already observed, founded on nothing
better than fair, but fallacious analogy. The principle
which they tend to establish stands in the most direct opposi-
tion to the result of experiment—sacred experiment! the on-
ly unerring guide to conduct the candid enquirer to the ever-
lasting temple of truth. Did our learned author (I would
beg leave to ask) ever faithfully experiment on separate por-
tions of the blood, drawn from different parts of the body, in
order to determine the comparative proximity of each portion,
to the putrefactive state? I presume he never did, otherwise
his opinion on this subject would have been, doubtless, very
different from what we find in his ingenious publication.
For it is a truth, nothing the less sacred and respectable on
account of its novelty, that if equal quantities of blood be
taken from the vena portarum, and from the lungs or any part
of the arterial system, and exposed to the same incumbent
circum- 

31 OF THE BILE.
in all animals possessing red blood, it exists no less
generally and uniformly than the heart itself.
circumstances, the pulmonic or arterial, will assume the putre-
factive process, much sooner than the hepatic, blood. The
cause of this phenomenon must be sufficiently obvious to any
one acquainted with the late discoveries, in the divine science
of chemistry. We would attempt its solution in the follow-
ing manner.
Vital air (which is indeed the genuine septic principle, if
any such principle exist) is in all cases essential to the progress
of putrefaction. This air, or rather its base (termed oxygene
by the ingenious chemists of France) is, as we have the strong-
est reasons to believe, from the experiments of Goodwyn,
Beddoes, Girtanner, and others, intimately blended with the
circulating blood in its passage through the lungs. As the
blood proceeds in its mazy route through the different parts
of the arterial system, it is gradually robbed of its concommit-
tant oxygene or base of vital air, by the mysterious action of
the animal system. The consequence of this spoliation is,
that the florid arterial, assumes a much darker colour, and suf-
fers finally a complete transmutation into venous blood. In
this latter state the putrefactive process is less apt to com-
mence, because the blood contains less oxygene in a state of
intimate mixture, or perhaps I might with more propriety
say, in a state of combination. For in proportion as the base
of vital air is more intimately blended with, and therefore
more nearly approximated to, the constituent parts of the
blood, the more powerfully can it co-operate with other aux-
iliary agents, in inducing these parts to assume that intestine
motion, which constitutes the putrefactive process. Although
our learned author is decidedly of opinion, that putrefaction
commences more readily, if vital air be excluded altogether
from 


32 OF THE BILE.
§ 375.
The substance of the liver is of a nature, sui
generis, and may be readily distinguished, at first
from the putrefying substances, yet it is now well known,
that the very reverse of this is true. Exclude vital air from
a body, in the composition of which none of this energetic
fluid exists, and you thereby embalm that body in a degree
equal, if not superior to the embalmment of the unperishable
mummies of the East.
No body, whatever, is capable of taking on the putrefac-
tive process, that does not contain in its composition more
or less of those simple substances that belong to the class of
inflammables. Reasoning therefore a priori, or climbing the
arduous steeps of science by the more laborious steps of expe-
riment and observation, we are warranted in either case to
conclude, that putrefaction consists, in a very considerable
degree, in the intimate combination of the base of vital air to
certain substances of an inflammable nature. Both the pri-
mary elements of which putrefiable bodies are composed, and
also the results of actual putrefaction, co-operate in the esta-
blishment of the same conclusion.
It is certainly a truth, that vital air is as essential to the
putrefactive process as it is to the support of combustion, or
the continuance of animal life.
Upon the whole, we may without the smallest hesitation
conclude, that the former opinions of physiologists respecting
the supposed putrescent disposition of the hepatic blood, are
wholly insupportable by argument or fact, being indeed di-
rectly opposed to the literal result of positive experiment;
2 and 


33 OF THE BILE.
sight, from that of all the other viscera of the
body: it consists of a parenchyma of a well known
colour and very tender texture: this parenchyma
is abundantly supplied with nerves, with lympha-
tic vessels (very visible on both surfaces), with bi-
liferous ducts, and finally with blood-vessels, from
whence these ducts originate: with respect to
these blood-vessels, some of which are remarkably
large, we will immediately state a few observations
on each of their several orders.
§ 376.
The first vessel which here presents itself for
our consideration is, the vena portarum, which
differs very widely from every other portion of
the venous system, not only in its singular appear-
ance, but also in the peculiarity of its course and
distribution, of which a few words were spoken
on a former occasion (§ 87). This large vessel
is formed by the conflux of by far the greater
number of the venous branches that originate and
run from the viscera, situated in the lower part of
the abdomen, and is invested and strengthened by
and therefore, that the pious eulogia so profusely bestowed
on the powers of the animal economy, in being able to form
an antiseptic out of a highly putrescent fluid, appear to be as
visionary and hypothetical, as nature's final intention in the
preparation of this fluid was thought to be beneficent, and her
process itself beautiful, and interesting.
VOL. II C a cel- 

34 OF THE BILE.
a cellular covering, commonly known by the name
of capsula Glissonii. No sooner does this trunk
make its entrance into the liver, than it is divided
into several branches, which as they run in vari-
ous directions through its substance, suffer still far-
ther divisions, till they are finally encreased to a
countless number of the most subtle ramifications,
which pervade, with the utmost minuteness, every
portion of this viscus. This whole system of the
vena portarum was formerly compared, by Galen,
to a tree, the roots of which are dispersed through- 
out the whole cavity of the abdomen, while its
branches are enclosed in the more contracted vo-
lume of the liver.
§ 377.
Another blood-vessel of a different kind, with
which the liver is furnished, is the arteria hepatica.
This vessel originates from the cæliac artery, and 
although far inferior to the vena portarum, both
in its capacity and in the number of its branches, 
is, notwithstanding, divided into ramifications of
astonishing subtility, and is also distributed with a
great deal of minuteness throughout every part of
the liver.
§ 378. 
The extreme terminations of both the forego- 
ing kinds of vessels, end in genuine veins, which
gradually 


35 OF THE BILE.
gradually uniting, form by their general conflux,
certain large venous trunks, that lose themselves
finally in the inferior vena cava.
§ 379.
Those extreme terminations, by which these
small branches of the vena portarum and arteria
hepatica become radicles to the vena cava, form
a very subtle vascular texture, exhibiting a singu-
lar and striking appearance, as if the vessels were
convoluted, or wound up into globes of incon-
ceivable minuteness. These globular bodies im-
posed so effectually on Malpighi, as to induce that
illustrious physiologist to consider them as glandu-
lar, hexagonal, and hollow kernels, destined to
constitute the immediate chambers of secretion.
§ 380.
From those same globular convolutions of blood-
vessels arise, lastly, the pori biliarii. These are
very tender ducts, which convey the gallish liquid
from the blood, and completely eliminate the same
from the system of the liver, through the ductus
hepaticus communis, a canal which they form by
their general conflux.
§ 381.
It is common for physiologists to enquire,
from what kind of blood the bile is immediately
C2 secreted; 

36 OF THE BILE.
secreted; whether from arterial, or from that con-
tained in the vena portarum?
Although the former of these opinions appears,
on the first view of the subject, to be rendered
most probable from the analogy of other secre-
tions, which are evidently the result of arterial
action, yet from a more accurate investigation of
the matter we will readily be convinced, that by far
the greater part, if not indeed the whole, of the bi-
liary secretion, is derived from the vena portarum:
the blood of this vessel being lurid, and highly im-
pregnated with phlogiston, corresponds precisely
with the nature of the bile; but how extremely
different, on the other hand, are the habit and
constitution of the florid and fiery arterial blood,
which the cæliac artery transmits from the aorta
immediately to the liver!
With respect to arguments drawn from analogy
we may observe, that as the vena portarum is sub-
jected to an arterial distribution, so it may, in like
manner, possess the power of performing an arte-
rial function: this same opinion, for which we con-
tend, appears also to derive additional support 
from the analogy which exists between the liver
and the lungs: to perform the leading function of 
these last mentioned viscera, is doubtless the imme-
diate destination of the large pulmonary arteries; 
whereas, 

37 OF THE BILE.
whereas, on the other hand, the bronchial artery
is only subservient, to the nourishment of the parts,
on which it is distributed:—the discharge of an
office, similar to this latter, is also, if we be not
greatly deceived, the more immediate destination
of the arteria hepatica. Notwithstanding what
we have here advanced, we are still ready to ac-
knowledge, that the hepatic artery may possibly
contribute somewhat towards the secretion of bile;
but, that its influence, in this respect, is indeed
very inconsiderable, and not yet sufficiently ascer-
tained and demonstrated, are positions to which
we subscribe with the utmost confidence.
§ 382.
The biliary hepatic liquor, when once secreted,
flows in a gentle but uninterrupted streamlet
through the hepatic duct; and, when the intesti-
num duodenum is empty, glides directly onward,
through the common ductus choledocus, into the
cavity of that viscus; but when the duodenum is
distended with chyme, it becomes necessary for
this fluid to pursue a different route, whence it
regurgitates from the hepatic, and flows through
the cystic duct into the gall-bladder, where it is
retained a certain time, and thence derives the
name of cystic bile.
C3 § 383.

38 OF THE BILE.
§ 383.
The gall-bladder is an oblong sack, somewhat
pyriform in its figure, attached to the concave su-
perficies of the liver, and composed of three mem-
branes or coats. 
These are, first, the external, which does not
invest the whole of the cyst, and is derived from
the peritoneum.
Secondly, the middle, usually called the nervous
coat, which, as in the stomach, the intestinal tube
and the urinary bladder, constitutes here likewise
the principal part of the tone and firmness of the
sac.
And, lastly, the internal, which bears a certain
similitude to the internal membrane of the stomach
(§ 359.); like that it is interspersed with an infi-
nitude of minute blood-vessels, and like that it is
also marked by rugæ or wrinkles, which form,
here and there, fine net-like checkerings, that ex-
hibit the appearance of the most exquisitely ele-
gant lattice-work.
§ 384.
The neck of the gall-bladder is conical, and
forms, by its termination, the cystic duct, which
pursues 
 

39 OF THE BILE. 
pursues not a direct, but somewhat circuitous or
serpentine route, and is furnished with a few mi-
nute valves of a lunated or falciform figure.
§ 385.
The gall-bladder retains the bile, when once
received, till that liquor either flows out spontane-
ously, in consequence of being favoured by a re-
clined and somewhat supine position of the body,
or till it is emulged from the cyst by the pressure
of the neighbouring intestines, namely, the jeju-
num and ileum, or by the occasional passage of
hardened fæces through the transverse colon.
Different stimuli acting on the duodenum have
also the effect of soliciting a more copious effusion
of bile into the cavity of that intestine.
The remarkable contractility of the gall-blad-
der, evidenced and satisfactorily established by live
dissections and certain pathological phenomena,
(although this sac be indeed completely destitute
of all genuine irratibility), (§ 307.), will appear
to contribute, not a little, to the excretion of the
bile; especially when we consider the stimulant
impression which this fluid, after retention in the
cyst, must make on its surrounding parietes or
walls.
C4 § 386. 
 

40 OF THE BILE.
§ 386.
For although the cystic exhibits, in its general
properties, the most striking similitude to the he-
patic bile (§ 382.), it is notwithstanding concen-
trated, as it were, by rest and stagnation, and
thence rendered more tenacious and bitter: this
effect appears to be owing, in a particular man-
ner, to the lymphatic vessels of the cyst, which
slowly absorb the aqueous parts of the bile, while
thus enclosed and retained in a quiescent state.
§ 387.
We proceed now to the consideration of the
bile itself. This is an animal fluid of the highest
dignity and importance in the living system: its na-
ture and uses have, for twenty pears past, laid a
foundation for more literary controversies among
physiologists, than have existed respecting any
other fluid that belongs to the body of man.
What we shall advance on this subject will re-
late immediately to the cystic bile, as this is to be
esteemed the more perfect of the two, and is there-
fore in a state more favourable for successful in-
vestigation.
§ 388.
Bile, taken from the recent corpse of an adult
subject, who had not previously laboured under
any 


41 OF THE BILE.
any disease, is a liquor somewhat viscid, of a faint
green colour, inclining towards a brown, inodo-
rous, and, if compared with the gall of brutes, of
a slightly bitterish taste.
§ 389.
Although the constituent parts of this fluid nei-
ther separate from each other spontaneously, nor
yet by so simple a mode of treatment as is sufficient
to produce that effect on the parts that compose
the blood, they may, notwithstanding, be subject-
ed, without much difficulty, to such an examina-
tion as will make it appear, that they doubtless
possess and exhibit a certain analogy to the ele-
mentary parts of the blood, though this analogy
should not be pursued to too great an extent.
The bile contains, in the first place, an aqueous
menstruum, which has been denominated by some
late physiologists, its salivary part: this may be
aptly enough compared to the aqueous portion,
and resembles also, though not in every particu-
lar, the serum of the blood.
From the bile we can also separate and procure
a small portion of a white and grumous substance,
which may be said to possess a certain, though re-
mote resemblance to the plastic lymph of the
blood.
Finally,

42 OF THE BILE.
Finally, the most striking and important princi-
ple which the bile contains is the matter of phlo-
giston, derived in large quantities from the blood
of the vena portarum, which is highly impreg-
nated with this subtle element.
§ 390.
This active inflammable part evidently manifests
its existence in dried bile, but more especially in
gall stones, by bursting immediately into flame,
when placed in contact with a burning substance.
To the action and influence of this principle must
we attribute those striking and singular qualities,
formerly enumerated, such as colour, taste, &c.
which serve to distinguish the bile from the other
inquiline humours belonging to the system; and
from the same source must we also derive the other
remarkable properties of this fluid, which shall be
mentioned hereafter.
§ 391.
The bile is not of such a nature as to possess,
like soap, an equal affinity to oil and water, and
thus serve to mix and intimately combine these
two elements together. The contrary opinion
(which was erroneously entertained on this subject
by Boerhaave, and afterwards by Schroder) was
formerly invalidated and refuted by certain re-
markable experiments of my own (since confirmed
and 
 

43 OF THE BILE. 
and further increased by other writers), and is
now entirely repudiated by the greater number of
physiologists. On the other hand, if bile be ap-
plied to the two foregoing elements, i. e. oil and
water, when in a state of intimate mixture and
combination, it produces an evident disunion and
separation of them from each other. This fluid
possesses indeed no alkaline properties, but is, not-
withstanding, equally unfriendly to the existence
of acid acrimony, to fermentation, and to putre-
faction.
§ 392.
By considering with due attention the foregoing
observations, we may easily ascertain the true, the
important, and the diversified uses of the bile, in
the process of chylification.
For in the first place, from that equable and
uniform chymous pulp which the stomach has dis-
charged into the duodenum, which the pancreas
has diluted by an effusion of its own juice, and
which moves spontaneously onward to the cavity
of the small intestines, it gradually precipitates the
fæces, and thus separates from them that cream-
like fluid denominated chyle.
The 

44 OF THE BILE.
The bile itself suffers, at the same time, a divi-
sion into two parts, the one aqueous, the other
phlogistic. The latter part adheres to the fæces,
tinges them, and is afterwards discharged, along
with them, out of the body; whereas the former
appears to be mixed with the chyle, and re-con-
ducted back to the mass of blood.
Thus the abundant phlogiston, new become
troublesome and noxious to the blood, is first di-
rected to the liver, where it is rendered subservient
to the formation of a singular and very important
humour: After this humour has fully answered
the end of its destination, its superfluous, or rather
noxious part is included among the excrements,
and finally eliminated from the system.
A further use of the bile is, to evolve and ex-
terminate from the alimentary canal, the fixed air,
which had been hitherto confined among the chy-
mous mass: it appears also to act on, and aid, the
intestinal tube, by means of its stimulus, thus ex-
citing it to perform its peristaltic motion with
greater vigour and energy.
I silently pretermit a variety of other uses, com-
monly attributed to the bile, which appear to me
to rest on more doubtful and equivocal evidence,
such, 


45 OF THE SPLEEN.
such, for instance, as its power of regurgitating
into the stomach when empty, and thus exciting
appetite, a phenomenon that, in my opinion, can
very seldom occur in a well formed and healthy
human subject.
SECT. XXXI.
OF THE FUNCTION OF THE SPLEEN.
§ 393.
THE spleen is very intimately connect-
ed with the liver, not only by an intercourse of
vessels, but also by the affinity and subserviency of
its function: it is situated in the left hypochon-
driac region, opposite to the liver; its figure is
oblong, generally, indeed, accommodated to the
situation of the neighbouring viscera with which it
lies in contact: it is subject however, to multiplex
varieties with regard to form, number, and other
species of lusi naturæ, or preternatural pheno-
mena.
§ 394.
Its colour is livid, its texture altogether singu-
lar, being soft, friable, easily lacerated, and there-
fore 

46 OF THE SPLEEN.
fore securely protected by two membranous cover-
ings, the internal of which belongs properly to
the spleen itself, while the external appears to be
derived from the omentum.
§ 395.
The situation and size of the spleen are now and
then, no less than its figure, subject to striking
and singular variations, arising in a great measure
from the different states of the stomach, with re-
spect to fulness and depletion: thus, for example,
when the stomach is empty, and hangs in a loose
and depending position, the spleen is distended
with blood; but when the former viscus becomes
turgid again, the latter is emulged, and conse-
quently diminished in bulk by the pressure to
which it is subjected.
The spleen is also agitated by another perpetual,
though gentle and uniform motion, in consequence
of respiration, being subjected to the immediate
action of a primary instrument of that function,
namely, the diaphragm.
§ 396.
The texture of the spleen, physiologists former-
ly supposed to be cellular, and uniformly compared
it to the corpora cavernosa of the penis: this opi-
nion, however, is evidently founded in error, and
has 

47 OF THE SPLEEN. 
has been very satisfactorily refuted by a more ac-
curate examination of the human spleen. For,
from such examination we learn, that almost the
whole volume of this viscus is composed of blood
vessels, extremely large in proportion to its size;
so that it is supplied with a greater profusion of
blood, than any other part belonging to the body
of man.
§ 397.
The splenic artery, conspicuous (agreeably to
the experiments of Wintringham) on account of
the astonishing fineness and strength of its coats,
is divided into an infinitude of minute ramifica-
tions, which constitute finally, by their evanescent
extremities, very small pulpy pencils: these pencils
afford origin, again, to fine filiform veins, that
constitute by their gradual confluence, large and
lax trunks highly capable of dilatation.
§ 398.
This vast congeries of blood vessels, is, how-
ever, knit together and supported by a small quan-
tity of cellular parenchyma, from whence the ab-
sorbent vessels arise, the trunks of which run on
the plain or flat side of the spleen, between the
two membranous coverings, of which we have al-
ready spoken.
§ 399.

48 OF THE SPLEEN.
§ 399.
This texture of the spleen, so very lax and high-
ly capable of admitting blood, corresponds admi-
rably with what we formerly said respecting the
sanguineous distension of this viscus (§ 395): and
we may further observe, that the phenomena of
the congestion, and tardy progressive motion of this
crimson fluid in the spleen, considered in conjunc-
tion with the nature of the surrounding and conti-
guous viscera, tend not a little to illustrate the pe-
culiar state and condition of the splenic blood,
which of themselves appear to shed considerable
light on the function of this mysterious viscus, a
subject of such repeated controversies among phy-
siologists.
§ 400.
The blood contained in the veins of the spleen
is very fluid, dissolved, coagulated with the utmost
difficulty, and admits of but a slight and partial
separation of the serum from the crassamentum;
its colour is also livid and obscure, as in the fœ-
tus; all which phenomena appear evidently to
combine in ascertaining and even demonstrating
the presence of an abundant quantity of the phlo-
gistic element. That this element is, however,
unequivocally present in large quantities, I further
ascertained to my entire satisfaction, by the follow-
ing simple and conclusive experiment: to the ac-
I tion 

49 OF THE SPLEEN. 
tion of pure dephlogisticated air, I exposed recent
sections and slices of the spleen of a human subject;
no sooner were these pieces brought in contact
with this vital fluid, than they were overspread
with a very florid and beautiful crimson blush,
while the air itself, thus despoiled of its native
fire, was on the other hand, contaminated by the
splenic phlogiston.
§ 401.
When we contemplate the foregoing circum-
stances collectively, and consider in the last place,
that the spleen is the only viscus of a similar nature
wholly unfurnished with any vestige of an excre-
tory duct, save those vessels which we have alrea-
dy said run to the liver, we are obliged from the
force of concurring testimony to conclude, that
the sole office of the organ now under considera-
tion, is to act in subserviency to the function of the
liver, and contribute towards the formation of
bile by the co-operation of its phlogistic parts.
§ 402.
This opinion is still farther substantiated by a
very curious and useful observation, made on such
individuals of the animal kingdom, as have been
deprived of the spleen by excision. It appears
that in animals subjected to this operation (which,
however singular and seemingly barbarous, has
VOL. II. D been, 

50 OF THE OMENTUM.
been, notwithstanding, very frequently performed
from remote periods of time) the cystic bile has
been uniformly afterwards found to be pale, weak-
ly impregnated with phlogiston, and disposed to a
grume-like coagulation of its lymphatic portion.
SECT. XXXII.
OF THE FUNCTION OF THE OMENTUM.
§ 403.
THE omentum gastrocolium, or omentum
magnum, (so called to distinguish it from the par-
vum or hepaticogastricum), is indeed a very singu-
lar production of the peritoneum, originating im-
mediately from the external coat of the stomach.
§ 404.
For notwithstanding the continuations of the
peritoneum, in the abdominal cavity, be almost innu-
merable, and although all the parts contained in
this cavity, whether viewed collectively or indivi-
dually, be so uniformly invested by it, that, on
opening the abdomen, it is impossible to discover
a single viscus which this membrane does not em-
brace, yet the modes in which it furnishes this
covering 

51 OF THE OMENTUM.
covering to the several viscera, are so diversified,
as to merit a division into different classes.
Thus, for example, the abdominal cavity con-
tains certain parts, over which the peritoneum is
only spread in such a partial and simple manner,
as to invest but one of their surfaces; this obser-
vation may be applied particularly to the kidneys,
the intestinum rectum, the vesica urinaria, and in
some measure also, to the pancreas and gall-
bladder.
There are also other viscera, which, notwith-
standing their attachment and adhesion to the sur-
rounding parietes of the abdomen, yet project also
to a considerable distance into the abdominal ca-
vity itself, and derive from the peritoneum a co-
vering, which invests, by far, the greater part of
their external surfaces: of this description are the
liver, the spleen, and even the stomach and female
uterus, to which we may add, finally, the testes
of a male fœtus, previously to their descent into
the scrotum.
Considerably different again, (in point of peri-
toneal covering), from both the foregoing classes
of viscera, is the whole of the intestinal tube, ex-
cept that portion which is denominated intestinum
rectum. This tube passes through the adominal
D2 cavity 
 

52 OF THE OMENTUM.
cavity in such a manner, as to carry along with it,
two remarkably broad processes of the peritoneum,
namely the mesentery and mesocolon, to which it
adheres in a state of suspension: under the same
class with the two preceding processes, may we
also arrange those singular peritoneal productions,
denominated the broad ligaments of the uterus.
§ 405.
But finally, the most extensive of all is that pe-
culiar continuation of the peritoneum called the
omentum. This production is a large empty sac
of a very delicate texture, that hangs in a depend-
ing position from the great curvature of the sto-
mach; it is spread over the region of the small in-
testines in particular, nicely adapts itself to their
irregular convexities, and dips down, in some
measure, into their numerous interstices.
§ 406.
Besides the blood vessels by which the omen-
tum is painted, it is also marked by numerous
striæ or broad lines of adipose substance, which
meet, intersect, and thus form a variety of reticu-
lar intertextures, from whence the membrane has
received the name vernaculum. In persons dis-
posed to obesity this adipose substance encreases
now and then to such a size, as to become not only
troublesome but even dangerous: it is also this
adipose 

53 OF THE OMENTUM. 
adipose portion that affords origin to that oily
halitus by which the omentum is constantly sur-
rounded and moistened.
§ 407.
It has been the opinion of certain celebrated
characters, and a further attempt was made by
the illustrious Haller to prove, that the fat con-
tained in the omentum is destined to be taken up
by absorption and conveyed to the liver, for the
purpose of supplying the bile with its oily portion,
&c. With respect to the truth of this opinion,
however, I must still be permitted to entertain and
express a serious doubt, having never yet been
convinced that sound, uncontaminated, bile con-
tains any oil; nor have I ever been able to disco-
ver any orifices subservient to such an absorption,
not even in frogs themselves, where Malpighi al-
leged, and even attempted to prove, their exis-
tence; much less in that part which is the subject
of our present consideration, namely, the omentum
of man.
§ 408.
What appears, from the nature and situation of
the part, as well as from the concurring belief of
all physiologists of the present day, to be a much
more unequivocal use of the omentum, is, to lu-
bricate the intestines, and by that means aid and
D3 facili- 


54 OF THE OMENTUM.
facilitate their perpetual motion. The same ap-
pear also to be the use and destination of certain
similar, but small, adipose bursæ, by which the
colon and rectum are invested.
The omentum also further serves to prevent the
occurrence of an adhesion between the intestines
and peritoneum, by which the whole office of the
primæ viæ would be subverted.
§ 409.
That this adipose curtain is destined to serve as
a defence against cold, (though an opinion very
generally received), appears, notwithstanding, to
rest on evidence of a more questionable nature:
the omentum of a man in perfect health, which
ought by no means to be burthened with an accu-
mulation of fat, is indeed, but very illy calculated
to answer such an intention.
When we consider, in the mean time, the sin-
gular structure of the two omenta, more especially
of that denominated omentum parvum or gastrohe-
paticum, it appears sufficiently probable, that be-
sides the uses already enumerated, the latter is still
destined for another, of, perhaps, even supreme
importance, which is as yet unknown to us, and
which future researches in comparative anatomy
will be alone able to develope.
SECT.

55 OF THE INTESTINES. 
SECT. XXXIII.
OF THE FUNCTIONS OF THE INTESTINES.
§ 410.
THE intestinal tube itself (before which
the omentum is spread, and into which we have
already seen the chyme conveyed, in order to be
further elaborated and sufficiently fitted for the
separation of chyle), is divided into two leading
portions, namely, the small and great; of the
functions of which we will now treat separately
and in order.
§ 411.
The small portion of intestines is again subdi-
vided into three parts, namely, the duodenum, je-
junum, and ileum.
The duodenum derives its name from the cir-
cumstance of its length.
The jejunum from that of its general habit, be-
cause, in a recent corpse, it appears collapsed and
empty as it were, even although it contain at the
same time a quantity of pulpy chyme. In the
third division, called ileum, the chyme deposits its
fæces, and suffers an evolution of its air, which
D4 had


56 OF THE INTESTINES.
had been hitherto fixed, so that this last of the
small intestines, being at the same time the longest,
and deriving its name from its circumvolutions,
appears more turgid, somewhat inflated, and mark-
ed here and there with small bubble-like emi-
nences, after the manner of the large portion of
this tube.
§ 412.
The coats of the small intestines are perfectly
similar to those composing the stomach, of which
we have already spoken (§ 359.)
The external is a production of the mesentery.
The muscular coat consists of two orders of
fibres, to wit, longitudinal, which are interrupted
in their course, and run rather externally, especi-
ally on that side of the intestine that looks in a
contrary direction from the mesentery; and more
internal, annular, or falciform fibres, which are
calculated to contract or narrow the diameter of
the tube; whereas the former are intended to di-
minish its longitudinal extent. On both the pre-
ceding orders of fibres depends that exquisitely
energetic and pertinacious irritability of the intes-
tines, of which we have spoken on a former occa-
sion (§ 306.)
The 


57 OF THE INTESTINES. 
The nervous coat consists of compacted cellular
membrane; and may, by a very simple mode of
treatment, especially by blowing into it, be again
reduced to a spongy, foam-like tissue: throughout
this coat a variety of blood-vessels, detached from
the mesenteric, are distributed in the form of ar-
borets or branching shrubs, of inimitable elegance
and beauty. As in the stomach, so likewise in the
intestines, the nervous coat is the principal seat of
tenacity and strength.
Finally, the internal coat (which merits more
unequivocally, in the small intestines, than in any
other part of the alimentary canal, the name vil-
lous), is continued here and there, in conjunction
with the internal surface of the preceding mem-
brane, into wave-like productions and rugous
folds, that in the intestines, when inflated and
dried, exhibit a falciform appearance, and are de-
nominated valvulæ Kerkringii.
§ 413.
Of the villi themselves, an immense number
overspread, in the closest order, the whole inter-
nal surface of the small intestines: their subtle and
exquisitely elegant vascular structure, was first dis-
covered and demonstrated by the labours of the
indefatigable Leiberkuhn. While the intestines
are destitute of chyle, the villi may be compared
in 

58 OF THE INTESTINES.
in some measure to small purses hanging in a loose
and flaccid position, and consisting internally of a
soft spongy texture; but when they become tur-
gid, in consequence of the absorption of this
milky fluid from the intestinal canal, their figure
undergoes such a striking change, as to bear no
small resemblance to the phallus esculentus *.
§ 414.
Those villi are surrounded, at their bases, by
an infinitude of small glandular follicles, which are
lodged principally in the nervous coat, and com-
municate by very minute orifices with the intesti-
nal cavity, into which they discharge a mucus that
serves to line and lubricate the whole internal sur-
face of that tube.
These minute glands are commonly supposed to
consist of three orders. First, the Brunnerian or
larger glands, which are separate from each other,
and situated principally on that part of the duode-
num, which lies next to the pylorus.
Secondly, the Peyerian, which are considerably
smaller, planted in clusters, and lodged, in parti-
cular, on the other extremity of the small intes-
* A species of fungus, denominated phallus, from its strik-
ing similitude to the male penis.
tines,

59 OF THE INTESTINES. 
tines, which looks towards, and is contiguous to,
the valve of the colon.
And, lastly, the glands of Leiberkuhn, the most
minute of all, of which about eight are said to be-
long to each villus.
It ought to be observed, however, that this di-
vision of the sources of mucus appears to rest on
very equivocal evidence. For if I be not greatly
deceived, both the Brunnerian and Peyerian
glands, as commonly exhibited in plates, are the
result of a vitiated and diseased state of the intesti-
nal tube. I am induced to entertain this opinion
from having never been able to discover, in the
sound small intestines of subjects carefully exami-
ned in different periods of life, the smallest vestige
of such fungous papillæ, perforated with orifices;
whereas, on the other hand, I have frequently
seen, in cases of aphtha, almost the whole intesti-
nal canal planted with countless numbers of them,
partly standing alone, and partly arranged in
crouded clusters. From considering the foregoing
circumstances, I feel a confidence in concluding,
that none can be accounted true muciferous
glands, except those extremely minute miliary bo-
dies, which, on gently separating the villous lining,
may be readily detected on its averted surface, but
cannot,

60 OF THE INTESTINES.
cannot, without great difficulty, be distinguished
on the side next to the eye.
§ 415.
It has been incontrovertibly established, not
only from that well known experiment first insti-
tuted (if I mistake not) by Pechlin, but also from
several others, that as the stomach, so in like
manner the cavity of the small intestines, is sup-
plied with a constant influx of a liquid, denomi-
nated, from the place into which it is discharged,
intestinal juice. It appears probable that this fluid
is similar in its nature to the gastric liquor, al-
though a more accurate investigation of it is, cer-
tainly as yet, a desideratum in physiology: nei-
ther can I venture to say any thing decisive re-
specting the quantity of this liquid secreted: I am,
however, fully of opinion, that Haller has been
too profuse in his estimate, where he alleges,
that this secretion amounts to eight pounds in the
space of twenty-four hours.
§ 416.
Further, it is also common to the intestines with
the stomach, to be agitated by a similar, but far
more lively and vigorous peristaltic motion, which,
in particular, while the chymous pulp is advancing,
onward, throws the same into gentle commotion,
by

61 OF THE INTESTINES. 
by a wavy and progressive constriction, and thus
propels it forward from the duodenum towards
the great intestines. For although we cannot ab-
solutely deny the phenomenon of an anti-peristal-
tic commotion, in consequence of which the intes-
tines are subjected to a retrograde action, it must,
notwithstanding, be acknowledged, that this, in a
healthy subject, is much feebler than the former,
that it occurs more rarely, and possesses a more
precarious and short-lived existence.
§ 417.
In consequence of the co-operation of those
energetic causes, hitherto enumerated (viz. both
the principles of motion, of which we have just
spoken, and likewise the solvent and alterative
powers of the inquiline humours that are every
where blended in abundance with the chyme), the
following remarkable changes are produced in this
heterogeneous mass:—in the jejunum it exhibits
the appearance of a more liquid pulp, possessing a
colour somewhat grey, and an odour slightly acid:
after its entrance into the ileum it begins to sepa-
rate into two portions; these are, first, the fæces,
marked by a pale yellow colour, inclining more
or less towards a brown, and possessing a fetid
odour; and, secondly, a white milk-like fluid, de-
nominated true chyle, which floats on the surface
of the fæces, and is separated from them by the
action 

62 OF THE INTESTINES.
action of the hepatic liquor or bile. This chy-
mous emulsion, designated by the name of chyle,
is destined to be received by absorption into the
lacteal vessels, through which mazy tubes we will
accompany it farther in the following section; and
shall, in the mean time, close the present, by tra-
cing, in as brief and intelligible a manner as pos-
sible, the route pursued by the residuary fæces.
§ 418.
These, therefore, after having become more and
more inspissated, in consequence of a tedious course
through the ileum, are obliged at length to pass
the valve of the colon, and thus enter the tract of
the great intestines; for which purpose the neigh-
bouring extremity of the ileum is furnished, and
lubricated internally, by a more copious quantity
of mucus, destined to destroy the friction of the
fæces, and consequently facilitate their transition
through the foregoing valve. 
§ 419.
The valve of the colon (denominated very justly
in honour of its real and illustrious discoverer,
valvula Fallopii), is a short continuation or process
of the ileum projecting into the cavity of the great
intestinal portion, by which it is surrounded and
closely embraced: the more exterior labia of this
process are so constituted, by means of a more
prominent 


63 OF THE INTESTINES. 
prominent or extensive ruga of the great intestine,
as to consist not only of its internal and nervous
coats (as is the case with the greater number of
such plicæ), but to contain also in its composition
some fibres from the muscular coat. Hence the
function of this valve appears to be twofold, to
prevent the premature passage of the fæces from
the small into the great intestines. and also to ob-
struct their regurgitation from the latter into the
former.
§ 420.
The great intestinal portion, which in like man-
ner with the small, is also divided into three sec-
tions, begins from the cœcum (to which is append-
ed the vermiform process, a part indeed of equivo-
cal use in the economy of an adult subject), and
constitutes collectively a canal so capacious, as to
admit the inspissated fæces to be gradually collected
and retained in its cavity, till a convenient oppor-
tunity for their evacuation.
§ 421.
As the great is superior to the small portion of
the intestines in diameter, so it likewise exceeds it
in the thickness and strength of its coats. The
muscular coat, in particular, possesses this peculia-
rity, that its longitudinal fibres (if we except the
lower part of the rectum) are collected into three
fasciculi 

64 OF THE INTESTINES.
fasciculi or bundles, called ligamenta coli; aud the
colon itself is thus divided into distinct segments of
a vesicular or cystiform appearance. The internal
coat in the great, is not of such a beautiful and
elegantly floccose appearance as in the small in-
testines, but possesses a nearer resemblance to that
which invests the cavity of the stomach.
§ 422.
The peristaltic motion appears to be less vivid
and active in the great, than in the small intestines.
On the other hand, the abdominal pressure is con-
siderably greater on the former than on the latter,
in as much as the whole colon is subjected to its
immediate action and influence.
§ 423.
The inspissated and hardened fæces contained in
the large intestines, are protruded slowly onward,
till having at length reached the rectum, they ex-
cite, by their stimulus on the internal surface of
that tube, a propensity to an evacuation. For the
purpose of facilitating this evacuation, ample and
wise provision is made, partly by a defect or inter-
ruption in the transverse rugæ, but more especi-
ally by a profuse quantity of mucus, that lubri-
cates the internal surface of the rectum near to its
extremity.
4 The 

65 OF THE ABSORBENT SYSTEM.
The evacuation of the fæces is, however, prin-
cipally accomplished by a downward direction of
the abdominal pressure, overcoming the resistance
of the coccyx and both the sphincters, the interior
of which is a very singular fascisculus or bundle
of annular fibres, but the exterior, a genuine cuta-
neous muscle: these ends being quite completed,
there succeeds an entire remission of the abdominal
effort, the intestine is retracted by the levator ani
in particular, and finally closed again by the con-
traction of the sphincters.
SECT. XXXIV.
OF THE FUNCTIONS OF THE ABSORBENT SYSTEM.
§ 424.
FROM observations delivered in a for-
mer section it is sufficiently evident, that the chyle,
which we left in the intestinum ileum, completely
disengaged from its fæces, is a compound of seve-
ral different humours. Although it be almost li-
terally impossible to calculate, with accuracy and
definitude, the precise quantity of inquiline hu-
mours, such as saliva, gastric juice, pancreatic juice,
intestinal juice, bile, &c. that is mixed and blended
VOL. II. E with 


66 OF THE ABSORBENT SYSTEM.
with the chyme, it appears, notwithstanding, a
matter of the highest credibility, that these several
humours, taken collectively, very far exceed, in
quantity, the other constituent part of the chyle,
which is derived immediately from alimentary sub-
stances, recently taken as nutriment. Hence we
may derive a solution of that problem in physio-
logy, by what means alimentary matters, though
of the most different and even opposite kinds, may,
notwithstanding, be converted into the same assimi-
lized, homogeneous, and milk-like chyle, equally
adapted to the nature, and calculated to serve as
the nutriment, of animals?
§ 425.
The channels through which the chyle must
flow, in its passage from the intestines to the mass
of blood, (the reservoir destined for its ultimate re-
ception), constitute a part of the absorbent system,
which we have hitherto mentioned only occasion-
ally, and in a very cursory manner, but will now
assume as the professed object of our present at-
tention. This system is divided generally into
four parts, viz. lacteal veins; lymphatic veins;
conglobate glands; and finally, the thoracic duct,
each of which shall constitute a subject of exclu-
sive consideration.
§ 426. 


67 OF THE ABSORBENT SYSTEM. 
§ 426.
With respect to the nascent origin of the lac-
teals from the intestines, there exists scarcely a
doubt, but that this is constituted by the innume-
rable villi of the internal intestinal coat, of which
we have already spoken. It is, however, still a
matter of controversy, whether the lacteals origi-
nate immediately from those villi themselves, or
only preserve a more distant intercourse and com-
munication with them, by means of interjacent
cellular substance. As far as my information has
extended, no one has hitherto been able, more
than myself, to trace the evanescent radicles of the
lacteal vessels to the villi themselves, with such
clearness and definitude, as to discover an imme-
diate and unequivocal connection between the
parts; on the other hand, the lacteals appear here
and there, throughout the coats of the intestines,
to form trunks of considerable size, immediately
after their orgin, and, (if a conjecture be allow-
able), to absorb from the cellular substance of the
adjacent parts, that chyle which had been origi-
nally taken up from the cavity of the intestines by
means of the villi themselves. This phenomenon
I think I have frequently observed, in young pup-
pies, into which I had poured, according to the
celebrated experiment of Lister, a solution of In-
dian blue, one or two hours before subjecting
them to the operation of live-dissection.
E2 § 427. 


68 OF THE ABSORBENT SYSTEM.
§ 427.
Those trunks, of which we have just spoken,
frequently run the distance of several inches, and
sometimes even wind about in angling or mean-
der-like directions, immediately under the external
coat of the intestine, previously to their entrance
into the mesentery.
§ 428.
During their passage through the mesentery,
these trunks make frequent entrances into small
mesenteric glands, which may be divided into two
different series or orders. Those of the first order
are situated in the vicinity of the intestinal tube,
and resemble, in their appearance, small beans ly-
ing separate from each other. The glands of the
other order, lie nearer to the receptacle of the
chyle, are superior in magnitude, and planted in
collective clusters.
§ 429.
Both the foregoing kinds of glands appear to
be in reality nothing else, than round compacted
convolutions: of the lacteal vessels themselves, co-
vered and interspersed with an infinitude of minute
blood-vessels: their destination appears to be, to
retard the progressive motion of the chyle, in or-
der, perhaps, that, by such delay, it may be more
fully and perfectly animalised and matured, previ-
ously 

69 OF THE ABSORBENT SYSTEM. 
ously to its entrance into the thoracic duct, and
subsequent admixture with the circulating volume
of the blood.
§ 430.
It has been proposed as a physiological question,
whether or not the large, possess also lacteal veins,
in common with the small intestines? The affirma-
tive of this has been zealously advocated, and its
defence attempted by arguments drawn from the
influence and efficacy of specific enemas, of ene-
mas composed of nutrimental substances, of ine-
briating substances, &c. and also from the follow-
ing well known circumstance, viz. that the longer
inspissated fæces are retained in the large portion
of the alimentary canal, the more indurated and
insucculent they are uniformly found. But al-
though these arguments do not satisfactorily de-
monstrate that any genuine chyle is absorbed from
the fæces after their transition over the valve of
Fallopius, they furnish, notwithstanding, additional
evidence in confirmation of that, which has indeed
been long since established on the testimony of
the sense of vision itself, namely, that the great in-
testines abound with a sufficiently plentiful appa-
ratus of lymphatic veins, perfectly similar to the
lacteals both in their structure and functions: in
testimony of this entire similarity, it may be proper
to observe, that when the intestines are destitute
E3 of 

70 OF THE ABSORBENT SYSTEM.
of chyle, the lacteals of the mesentery are then
engaged in the absorption of lymph.
§ 431.
Another question, more important and difficult
of solution than the former, is, whether or not
the whole of the chyle, absorbed from the cavity
of the small intestines, be conveyed to the blood
through the same public, and royal route, as it is
termed, or whether there do not exist certain se-
cret channels, through which it may glide surrep-
titiously onward, to mingle its streamlets with the
general current of circulating blood?
It must indeed, be confessed, that most of the
arguments, by which physiologists have endea-
voured to prove a private absorption and convey-
ance of chyle through the sanguiferous veins, do
not appear to rest on a very solid foundation:
thus the assertion of Ruysch, that on the approach
of old age the mesenteric glands become so indu-
rated and constricted, as to be rendered unfit for
performing their functions, has been long since re-
futed, and it has, on the other hand, been satis-
factorily demonstrated that, different affections of
these glands, such as swellings, &c. very errone-
ously pass under the common name of obstructions, 
while, at the same time, their vessels remain in a
state sufficiently pervious to afford a very easy en-
trance 

71 OF THE ABSORBENT SYSTEM. 
trance and transition to injections of quick silver.
That well known phenomenon, from which it is
ascertained, that tepid water, thrown into the inert
mesenteric veins of a dead subject, transudes into
the cavity of the intestines, appears to contribute
but very little towards the satisfactory elucidation
of any function of the human body while in a
living state; much less can we repose confidence
in the evidence derived from that bicrural and two
branched tube of copper, which was invented by
Lieberkuhn, for the purpose of confirming the
same opinion. As to the assertion, that chyle has
been unequivocally detected in the red veins of
the mesentery, it appears to me to stand in need
of farther evidence for its unquestionable confir-
mation; on the whole, I have never yet been
convinced, that those veins convey any thing else
than blood very highly charged with phlogiston,
destined for the secretion of bile.
§ 432.
Finally, the ultimate trunks of the lacteal veins,
(with certain other tubes very similar in appear-
ance and function, which are formed by the con-
fluence of a great number of minute lymphatic ves-
sels), unite and constitute by their junction, the
receptacle or cistern of the chyle, which is a name
given by physiologists to the inferior and larger
E4 portion 


72 OF THE ABSORBENT SYSTEM.
portion of the thoracic duct, called also the duct of
Pecquet.
§ 433.
This duct is a membranous canal, of a delicate
appearance and texture, yet sufficiently robust and
strong, more or less circuitous in its course, and
not unfrequently subject to very striking diversities
with regard to the direction in which it runs, and
the divisions it occasionally undergoes: it is equal-
ly destitute of muscular fibres and nerves, is fur-
nished here and there with small valves, and, after
having passed over the left subclavian vein, is again
reflected towards, and finally inserted into, the
same, and, at the very point of insertion, has its
entrance guarded by a valve of a peculiar struc-
ture.
§ 434.
The powers which produce and continue the
onward motion of the chyle, both in the lacteal
veins, and through the thoracic duct, are to be
attributed, indeed, principally to the contractility
of these vessels themselves, but, in part also, to
the valves with which they are furnished, to a
propulsive vis a tergo, and to the uninterrupted
puisation of neighbouring arteries.
§ 435.

73 OF THE ABSORBENT SYSTEM. 
§ 435.
It appears probable, that the principal destina-
tion of the valve, which is fixed, as has been al-
ready observed, in the entrance of the chyliferous
duct into the subclavian vein, is not so much to
obstruct the lateral passage of blood into this duct,
as to regulate the necessary discharge of chyle in-
to the vein, and prevent its admission in any other
manner than by a slow and gradual stillicidium.
By this means, adequate provision is made
against the simultaneous entrance of too large a
quantity of recent chyle, into the mass of blood.
Such an excessive influx of this crude fluid would
necessarily stimulate the parietes of the heart to ex-
ertions too violent and laborious, and would be
blended and assimilated by the same, with the ut-
most difficulty, and in an imperfect manner; that
this would be the result, we judge from the nature
of recent chyle, which is a compound of hetero-
geneous elements, derived not only from the pri-
mæ viæ, by means of the lacteal, but also from
all the other parts of the body, through the ave-
nues of the lymphatic vessels.
§ 436.
The lymphatic veins themselves, which consti-
tute a third part of the absorbent system, and bear
a very 

74 OF THE ABSORBENT SYSTEM.
a very close resemblance to the lacteals, both in
structure and in function, are so considerable, in
point of extension, as to pervade, perhaps, every
part of the human body; but originate, in parti-
cular, from the common external integuments,
from the pleura, the peritoneum, and viscera,
contained in the thorax and abdomen.
§ 437.
The manner in which they arise, is simliar to
the origin of the lacteals from the intestines, of
which we have already spoken. Thus each radi-
cle of each lymphatic vessel, is destined to absorb
from a neighbouring portion of cellular membrane,
(as from a territory of its own), the moisture it
contains, and propel it onward to the general cis-
tern of the chyle.
§ 438.
These lymphatic vessels are furnished in their
course, sometimes more frequently, sometimes
more rarely, with valves situated in bigæ or pairs.
By far the greater part of them enter conglobate
glands; those in the vicinity of each other fre-
quently anastomose; and such of them as over-
spread the surface of certain viscera, as that of the
lungs, the liver, &c. form exquisitely elegant reti-
cular expansions.
§ 439. 


75 OF THE ABSORBENT SYSTEM. 
§ 439.
To pass silently over certain other aids, suffici-
ently evident from former observations, the func-
tion of the lymphatics is greatly promoted by their
remarkable contractility, and the strength of their
delicate coats, which is sufficient, in processes for
anatomical preparations, to resist the pressure from
a ponderous column of quick silver: this function
is also further aided, especially in the joints, by
muscular motion, in consequence of which, the
lymphatics being compressed and closely embraced
on all sides, have their tone remarkably aug-
mented.
§ 440.
With respect to the terminations of the lym-
phatics, various controversies have lately existed
among physiological writers. Thus, while some
contend, that all those vessels unite in the thoracic
duct, (in like manner as the sanguiferous veins
unite in the venæ cavæ), others, on the contrary,
exempt from this general confluence, at least the
lymphatics of the right arm, and right side of the
neck, which they allege are not inserted into the
same duct, but into the right subclavian vein:
others again assert that in the conglobate glands,
the lymphatics communicate immediately with san-
guiferous veins; and lastly, others maintain (not
indeed without an appearance of probability) that
certain 

76 OF THE ABSORBENT SYSTEM.
certain lymphatic vessels *, actually exist, which
form a direct and free communication between the
intestinal tube and uropoietic organs.
§ 441.
Seeing therefore, the lymphatic vessels are
extended far and wide throughout almost the
whole system, and, especially, in as much as an
immense profusion of them originate on the cuta-
neous surface of the body, and may consequently
absorb such fluids as are applied from without, it
is sufficiently evident, that the lymph, when re-
cently absorbed, must be, indeed, a liquid compo-
sition extremely heterogeneous and diversified as
* For a great number of truly important observations
and highly interesting speculations on this subject, the reader
is referred to a short treatise, written by Charles Darwin,
"On the retrograde motion of the lymphatics," and pub-
lished at Litchfield in the year 1780, a considerable period
of time after the premature death of its ingenious author.
This young philosopher and physician appears to have been
peculiarly formed by nature, and happily finished by edu-
cation, to shed unequivocal light on subjects of a dark and
difficult nature in the science of medicine. He experimented
with accuracy and definitude, he observed with the utmost
attention, and he speculated with the highest ingenuity and
force. Unhappily for the healing art, and (perhaps I may
add) for science in all its various branches, this amiable
young philosopher was hastily summoned away, ere yet his
mind was perfectly expanded, or his plenitude of merit
announced to the world.
to

77 OF THE ABSORBENT SYSTEM.
to its nature and elementary parts: this diversity
is fully ascertained and established, by a more
careful and accurate examination of dead subjects,
where, for instance, the liquid contained in the
absorbents of the liver and spleen, appears to be
evidently different from that discovered in those
which run to the uterus.
§ 442.
Of the conglobate glands, (which constitute the
last branch of the lymphatic system), the prin-
cipal use and destination appear to be, to assimi-
late to the animal nature this subtle and hetero-
geneous fluid, especially that portion of it which
is absorbed by the lymphatics of the skin: this
assimilation they accomplish by retarding and in
some measure obstructing the motion of the lymph,
and perhaps also by the addition of a new fluid,
derived from the minute arteries, with which they
very plentifully abound. Hence a wise and ade-
quate provision is made, to prevent the humours,
while in too crude a state, from effecting a prema-
ture mixture with the blood, and thus the heart
is guarded in perfect security from their noxious
impressions.
§ 443.
With respect to those other glands of the same
nature, which are minutely dispread throughout 
by

78 OF SANGUIFICATION.
by far the greater part of the system, and planted
here and there in collected clusters, as in the
groin, beneath the axilla, &c. they bear, in every
respect, the most perfect resemblance to the me-
senteric glands, of which we have already spoken;
like them they are composed, in a great measure,
of the mazy convolutions of absorbent veins; like
them they are furnished with a vast profusion of
minute blood vessels; and finally, they are subject
to be readily invaded by the same diseases that
attack the glands of the mesentery.
SECT. XXXV.
OF SANGUIFICATION.
§ 444.
IT is scarcely necessary to observe, that
by the term sanguification, we mean the assimila-
tion of chyle to blood, and the constant and uni-
form restitution made by means of the former, for
the equally constant and uniform loss which is sus-
tained by the latter.
§ 445.
For on this principle depends that division of all
the humours of our body, into the three classes
(§ 4.

79 OF SANGUIFICATION.
(§ 4. 5.) of crude, sanguineous, and secreted; viz.
that the middle class embrace the whole circula-
ting volume of blood, from which the different se-
creted humours are derived in constant streamlets,
and to which the countless channels of the absor-
bent system convey their chyle, and the infinitude
of lymphatic tubes return their absorbed fluids in
currents equally constant and uniform.
§ 446.
Seeing the blood is an animal humour of so very
singular and exclusive a kind, as to be wholly dis-
similar to every other fluid yet discovered in any
department of nature, it is a proposition sufficiently
self-evident, that there must be a variety of assist-
ant powers which contribute, by their joint co-
operation, to incorporate and assimilize with the
blood, the heterogeneous and adventitious hu-
mours, which it is constantly deriving from the
thoracic duct.
§ 447.
The process of sanguification we may consider,
then, as first commencing under the action and
influence of those mazy circumvolutions (frequent-
ly spoken of already), which both the lacteal and
lymphatic veins exhibit occasionally in their courses
(more especially in the mesenteric and other con-
globate 

80 OF SANGUIFICATION.
globate glands), and which are, at the same time,
furnished with considerable quantities of what may
be called animal and inquisine contagion. 
§ 448.
It is necessary further to consider, that a great
part of the lymph, which enters the subclavian
vein (after having first effected a mixture with the
intestinal chyle in the thoracic duct), is derived
from the interior recesses of the viscera and other
soft parts of the body, and was formerly secreted
from the blood itself; from whence it necessarily
follows, that such portion of the lymphatic fluid
must doubtless possess, already, the animal nature
entire, and be very readily miscible with the mass
of blood to which it is returned.
§ 449.
To these we may add another circumstance, of
which we spoke on a former occasion, namely,
the slow and stillicidious transition of the chyle into
its reservoir, the blood—that fluid not being ad-
mitted to pass through the ultimate valve of the
thoracic duct into the subclavian vein, in any
other manner than by drops, in order that those
minute portions may, by this means, be more inti-
mately mixed and incorporated with the circu-
lating blood.
2 § 450. 

81 OF SANGUIFICATION. 
450
The internal structure of the heart itself appears
also to contribute, not a little, towards the im-
portant process of sanguification. Thus, by means
of those astonishing muscular papillæ, with which
the ventricles of the heart are plentifully fur-
nished, the blood and chyle (having recently met
together), are thoroughly agitated, and brought
into a state of more intimate combination.
§ 451.
That the lungs, receiving the blood, recently
impregnated with chyle, perform, by the function
of respiration, an important part in the further
assimilation of this crude fluid, will appear suffici-
ently evident to any one who considers the asto-
nishing vascular structure of these viscera (§ 136.)
in conjunction with the equable alternate motion
to which they are perpetually subjected, during
the continuance of human life.
§ 452.
The remaining part of the process of sanguifica-
tion is finally completed by the more extensive
circuitous journey of the blood throughout the
whole body, and by those powers which con-
tribute towards the continuance of the same,
more especially muscular motion, &c.
VOL. II. F § 453.

82 OF SANGUIFICATION.
§ 453.
But although potent provision be made, by
such powerful and diversified apparatus, for blend-
ing and intimately incorporating the chyle with
the blood, it appears, notwithstanding, that there
exists a certain similarity between the constituent
parts of those two fluids. It is very commonly
asserted, that a great many hours must elapse be-
fore the chyle can be completely divested of its
own milky colour, and perfectly assimilated to that
of the crimson fluid into which it is destined to be
converted: in testimony of the truth of this asser-
tion, medical philosophers usually adduce (besides
other arguments) the following singular patholo-
gical phenomenon, namely, that several hours after
the close of digestion, genuine chyle has been fre-
quently observed to flow from an orifice made in
a vein of the human body: this phenomenon I
have indeed had an opportunity of observing my-
self; but it was at the same time extremely evi-
dent, that the blood was then highly charged with
phlogiston (a condition of this fluid very un-
friendly to the regular assimilation of chyle), so
that from hence scarcely any inference can be
drawn relative to the healthy state of the system,
which is alone the exclusive subject of the science
of physiology.
SECT. 


83 OF NUTRITION.
SECT. XXXVI.
OF NUTRITION.
§ 454.
BESIDES that function (which we at-
tributed to the blood in a former section) of dis-
tributing the element of fire throughout the whole
body, and in its place wasting that of phlogiston
back to the lungs, two of its primary and leading 
offices appear to be, to convey to the body nou-
rishment, and to the secretory organs the matter
of those peculiar fluids which they are severally
destined to extract. Of this twofold function we
will next treat; and first of the function of nu-
trition.
§ 455.
Nutrition is the supreme privilege of nature.
It is a common and leading prerogative of all or-
ganized bodies, whether animal or vegetable, by
which they are instantly discovered, on first view,
to surpass, in an immeasureable degree, all ma-
chines and automatons constructed by human ar-
tifice: because on none of these latter has any
artist ever been able to confer a power (I will not
say of actual growth, of progressing toward matu-
rity, and of acquiring gradually higher and higher
F2 degrees
 

84 OF NUTRITION.
degrees of perfection), but not even of preserving
themselves in a state of stationary existence by their
own inherent powers, nor of repairing the gradual
losses to which they are subjected by attrition, by
incidental casualties, &c.
§ 456.
Nutrition is that faculty of our bodies, on which
all the sublime and astonishing functions of our na-
ture depend. By means of this faculty we increase
in magnitude from the earliest dawnings of our
existence, we advance through the expanding
period of youth, and finally arrive at our acme,
or point of complete maturity. It is also through
the instrumentality of this same faculty that a com-
petent remedy is applied, and sufficient restitution
made, for that uniform waste and loss of the body,
by which (while in a living state) it destroys and
in some measure consumes itself, by its own neces-
sary action.
§ 457.
With respect to the nature and mode of this
wasting or loss, various controversies have existed
among physiologists. The more immediate point
of disputation has been, whether such waste occurs
in the solid parts of our bodies, or whether it be
not more probable, that those parts, when once
formed and completed, remain stationary, without
being 

85 OF NUTRITION. 
being subject either to vitiation or change? which
latter is indeed an opinion embraced and taught
by several characters of the utmost acumen and
ingenuity.
§ 458.
With respect to some particular solid parts of
the body, such, for example, as the epidermis,
the nails, &c. there exists indeed not a shadow of
doubt, but that they are gradually destroyed and
again repaired; and with regard to the destruction
or waste and subsequent reparation of the bones
themselves, the testimony will appear equally plain
and conclusive, to any one who may consider with
attention the result of the well known experiments
made by feeding warm-blooded animals, for some
time, on the root of the rubia tinctorum, or who
may take the further trouble of contemplating
attentively the phenomena exhibited by certain
large plain bones, especially those of the cranium,
which in extreme old age become remarkably
attenuated, or diminished in thickness, in conse-
quence of the scanty nourishment with which they
are supplied at that period of life.
§ 450.
Upon the whole, if I be capable of judging
rightly, those solid parts appear to be not only
gradually consumed, and again repaired, by the
F3 faculty 


86 OF NUTRITION.
faculty of nutrition, but possess also a vis repro-
ductiva, or power of re-production. This latter
is indeed a surprising faculty, destined not only
to make restitution for the uniform removal of
minute atoms by the necessary action of the animal
economy, but also to repair the incidental loss of
larger parts (suffered in consequence of external
injuries, wounds, &c.), by a perfect restoration of
the substance of which the body has been thus
forcibly deprived. That such a power does un-
equivocally reside in the bones, and a few other
parts, of which we have just spoken, is with me
too well ascertained and substantiated to admit of
a doubt.
§ 460.
But on the other hand, from a variety of obser-
vations and experiments which I have made both
on man and other warm-blooded animals, this
power of reproduction appears to reside in scarcely
any other solid parts of the body than such as are
endowed with contractility alone, without possessing
at the same time any of the other vital energies,
such as irritability, sensibility, or finally, specific life.
§ 461.
Of those parts of the system therefore (which
possess the more exalted kinds of vital energy),
the staminal basis appears to me to consist of a pe-
rennial 

87 OF NUTRITION.
rennial parenchyma, which is subject neither to
genuine mutation nor decay, but only liable to
certain vicissitudes in point of bulk, that are pro-
duced in the following manner, namely, when
the process of nutrition is conducted with suffi-
cient activity and vigour, the cellular interstices of
the parenchyma, being uniformly filled with the rich
and plastic lymph of the blood, are, of course, dis-
tended, and the parenchyma necessarily enlarged;
but when, on the other hand, nutrition goes on
less favourably, these same interstices, being in a
great measure deprived of this nutritious lymph,
fall into a state of collapse, and the parts become
consequently diminished in size.
§ 462.
With respect to this plastic lymph (of the dig-
nity and importance of which we have spoken
fully on a former occasion), as it assumes with
great facility the appearance and nature of genuine
cellular membrane, so it appears to constitute ge-
nerally the principal nutritious matter of the
whole system, and is conveyed to every part of the
body by means of that infinitude of minute blood-
vessels, to which we have so often called the
reader's attention.
F4 § 463. 

88 OF NUTRITION.
§ 463.
During the time of the body's advancement in
growth, it appears to possess certain peculiar or
specific powers, by the aid of which the lymph,
being deposited from the evanescent extremities
of the sanguiferous vessels, into the surrounding
cellular membrane, is duly arranged, and com-
pletely assimilated to each particular portion, and
kind of parenchyma. To the head of these specific
powers, must we in part refer that particular law
of affinity, by means of which the partes similares
of the system attract and appropriate to themselves,
the homogeneous elements of the nutritious lymph,
more especially such of them, as possess reciprocal
and kindred propensities; and to the same head
may we also in part refer that nisus formativus, of
which we will have occasion to speak more fully
hereafter, and to which must be attributed, the
just and specific application of the rude, and hi-
therto formless, elementary matter, and its subse-
quent organisation and arrangement into the form
and figure of its peculiar destination.
§ 464.
It is, I presume, from the joint co-operation of
both the preceding powers, that we must princi-
pally derive the nutrition of those parts of the
body, which are not proximately supplied with any
blood 

89 OF NUTRITION. 
blood vessels at all; such as the nails, hairs, &c.
and which are, notwithstanding, generated at first,
by a very powerful and truly infallible nisus or ex-
ertion, are afterwards advanced in magnitude, and
regularly supported by nutriment throughout the
whole of life, and, finally, if by accident removed,
are again readily restored by the astonishing
efforts of the vis reproductiva.
§ 465.
Although the preceding appears to be a general
breviate account of the process of nutrition, yet,
on the other hand, it is evident that there exists,
in different individuals, a great many varieties,
with regard to the degrees and modes in which
this function is discharged. Thus, for example,
in proportion as a more lax or more close apposition
and union of the nutritious matter are effected, the
texture of the parts themselves is rendered more
dense or delicate, and hence also seems to origi-
nate the difference between the specific weight of
human bodies; in which respect it is well known,
not only that man differs from man, but even
nation from nation: in testimony of this truth it
may be sufficient to adduce even a solitary example
from among certain northern tribes, namely, the
Jukutæ, the Buratæ, &c. people highly conspi-
cuous on account of the remarkable and truly sin-
gular levity of their bodies.
SECT. 




90 OF SECRETION.
SECT. XXXVII.
OF SECRETION.
§ 466.
BESIDES those juices destined for
the important process of nutrition, there are also
in the animal system other humours, of a very
different order and character, which are extracted
for various purposes from the exuberant fountain
of the blood. These humours owe their exis-
tence to the process of secretion, than which no
function is less understood by physiologists; a
truth mentioned as a subject of just regret, both
by the immortal Haller and other preceding
writers.
§ 467.
The secreted humours, appear, in one point of
view, to be so extremely diversified in their na-
tures, and, in another, to bear so striking an affi-
nity to each other, that it is not possible to reduce
them to any, save highly arbitrary, classes. If,
however, in treating of these humours, we found
our divisions of them on the less and greater
changes to which their elementary parts, (con-
tained 


91 OF SECRETION.
tained in the mass of blood), are subjected in the
secretory organs, they may be aptly enough enu-
merated in the following order.
First, the milk, a fluid which we think proper
to place at the head of our census or enumeration,
because it may be considered, in some measure, as
renovated chyle, and appears to be secreted, by
the most simple process, from the blood, to which
the chyle had been recently united.
Secondly, the aqueous fluids; such, for exam-
ple, as the humours of the eye, and the tears:
to the same head must we refer in like manner,
the sweat; and also, (if our opinion be not un-
founded), that halitus which is contained gene-
rally in the interstices of the cellular membrane,
as well as in the cavities of the thorax and abdo-
men: this vapour appears to differ but very little
either from the liquor of the pericardium, or from
that subtle halitus by which the ventricles of the
brain, and the pituitary sinuses of the cranium are
preserved in a state of perpetual humidity.
Under the same head of aqueous fluids, it is
likewise common to arrange the urine, although
this is doubtless a liquid possessed of some singu-
larly striking and peculiar properties.
Of 
 

92 OF SECRETION.
Of a less compound nature are the salivary
humours, which, in office, are subservient to mas-
tication, to digestion, and to chylification.
Thirdly, the mucagenous fluids, which invest
and lubricate the cavities of most of the viscera,
that are destined to the performance of the natural
and genital functions, and also the internal surfaces
of all the aerial avenues belonging to the system,
such as the nares, the larynx, and the aspera
arteria.
Of a nature not widely different from the fore-
going, is that portion of mucus which covers the
internal segment of the eyeball; as well as that
which is spread immediately beneath the epi-
dermis.
Fourthly, the adipose humours are, in particular,
(besides the common fat itself), the medulla of
the bones, and the smegma or oily covering of the
skin, to which may be added the cerumen aurium,
or waxlike substance investing the external ave-
nues of the ears.
Of a nature nearly related to the foregoing, is
that unctuous secretion, so evident on the glans
penis of the male, and about the rima or os exter-
num, in the genital organs of the female.
Under 

93 OF SECRETION.
Under the same class may we also arrange that
oily substance, with which the glands of Meibo-
mius furnish and anoint the eyelids.
Fifthly, what are commonly denominated by
physiologists gelatinous fluids, examples of which
we have in the liquor amnii, and unguen of the
joints. Respecting the nature of these fluids,
however, we are not yet possessed of a sufficient
number of well authenticated facts to give birth
to unequivocal and satisfactory conclusions: a
similar observation may also be made, respecting
that uninvestigated and anonymous humour, which
the female uterus discharges during the ardent
glow of the venereal orgasm.
We remain also as yet, in a state of equal un-
certainty respecting the nature of that fluid, which
is lodged, during the first months after conception,
between the chorion and amnios; of that which
is contained in the umbilical vesicula or pouch of
the embryo in its tenderest state; and also of that
which is interposed between the three vessels that
constitute the umbilical cord.
The liquid enclosed in the vesiculæ graffianæ of
the female ovary, and also the liquor of the pros-
tate gland, appear to be of a truly serous or albu-
minous nature.
Sixth- 

94 OF SECRETION.
Sixthlly, the male semen appears to be a humour
so remarkably singular in its nature, as not to
admit of classification, nor even of comparison,
with any other.
And lastly, with regard to the bile, there is
equal room for the admission of a similiar obser-
vation.
§ 468.
That the foregoing secreted humours, so ex-
tremely diversified in their natures and habits, can
neither be derived from the mass of blood by the
same individual process, nor by organs of the same
kind, is a proposition too self evident to stand in
need of, or indeed leave room for, any farther
confirmation. Among these humours, there ob-
viously exists this memorable variety, namely, that
while some of them are secreted and conveyed
from the blood through a shorter route, others
again, are more elaborately prepared, by being
carried onward through tubes of greater longitu-
dinal extension.
§ 469.
Of all the modes of secretion, that must doubt-
less be considered as the most simple, in which the
secreted humour appears to transude immediately
through the coats of the arteries, by what physi-
ologists 

95 OF SECRETION. 
ologists call diapedesis. Instances of this mode we
have in the secretion of the fat, and of the medulla
residing in the bones, &c.; and, finally, it appears
to be by a modification of the secretory process,
not greatly dissimilar to the foregoing, that the
gastric liquor, the intestinal liquor, &c. are pre-
pared and discharged into the cavities of their
respective viscera.
§ 470.
The mechanism of secretion appears to be more
compound, where that process is performed by
means of glands, under which denomination we
generally include even follicles and cryptæ them-
selves; such, for example, as are easily discover-
able in the fauces; and which physiologists gene-
rally designate by the name of glandulæ sim-
plissimæ.
We bestow, with propriety, the denomination
of secreting glands, on those bodies which, (to
distinguish them from the conglobate, belonging to
the lymphatic system), are called conglomerate; ex-
amples of which we have in the salivary glands, in
the pancreas, in the lachrymal glands, and in the
mammæ, or breasts of females. The foregoing
glandular bodies are furnished with excretory
ducts, which are composed of tubes or canals
running immediately from their larger lobes: these
lobes,
 

96 OF SECRETION.
lobes, on being submitted to farther examination,
are found to be made up of smaller lobules, re-
specting the internal structure of which, there for-
merly existed very warm controversies in some of
the most celebrated schools of medicine. Malpighi
considered the small miliary globules, which may
be readily demonstrated in the greater part of
them, to be nothing else than genuine acini or
kernels, containing, each one, a minute cavity in
its centre. While Ruysch contended, on the
other hand, that those hypothetical excavated
kernels were nothing more than globular convo-
lutions of extremely fine blood vessels; which lat-
ter opinion, is doubtless founded on by far the
most unequivocal and substantial testimony, as
we readily learn from well conducted anatomical
investigations, more especially from successful
injections, and the assistance of glasses.
§ 471.
Nor does this structure (if indeed we keep out
of view the peculiar parenchyma of each parti-
cular viscus), differ much from, but appears rather
to shed a considerable gleam of light on, the struc-
ture of certain other secreting viscera, particularly
on that of the liver and kidneys, in which late ex-
perimenters have been able to demonstrate, with
the utmost perspicuity, certain spherical bodies
entirely similar to the globular convolutions of
4 Ruysch, 

97 OF SECRETION.
Ruysch, or the kernel-like substances of the cele-
brated Malpighi. For, in what is called the cortical
portion of those viscera, minute ramifications emerg-
ing from the sides of the small capillary arteries, be-
come presently convoluted, in such a manner, as to
form little vascular balls, which thus appear to hang
by those ramifications of which they are composed,
like so many small berries or grapes supported by
their footstalks. From these minute vascular balls
originate first, that very subtle and colourless
order of vessels immediately destined for the busi-
ness of secretion, (respecting the origin of which,
from the evanesceut terminations of arteries, we
transiently spoke on a former occasion, (§ 79.
81.); and secondly, the incipient radicles of veins,
into which the minute arteries are themselves
continuously reflected, and which conduct back
to the venous trunks, the residue of the blood
now deprived of those elementary particles neces-
sary to constitute the fluid recently secreted.
§ 472.
Finally, certain other parts of the body, appro-
priated entirely to the business of secretion, are
distinguished again by different and remarkably
peculiar, species of organization; thus the male
testes, for example, are wholly composed of no-
thing else than close and mazy convolutions of
very lengthy and numerous blood vessels, &c.
VOL. II. G § 473.

 

98 OF SECRETION.
§ 473.
We come now to the consideration of the pe-
culiar causes, by the operation and efficacy of
which those determinate and specific humours are
secreted in these corresponding determinate and
specific organs: this is indeed the Gordian knot—
this is by far the most difficult point of disquisition
in the whole doctrine of secretion—that point
which numerous doubts and difficulties yet invest.
§ 474.
It appears indeed to be a truth ascertained and
established beyond the faintest shadow of a doubt,
that the leading, and what may be called the
proximate cause of most of the secretions, must
be sought for in the internal structure of the se-
treting organs themselves: under this head we
must particularly consider, in the conglomerate
glands and other secreting viscera, not only the
peculiar distribution and direction of the extreme
blood-vessels, from which the humours are se-
creted, but also the parenchyma, so uniformly
proper to each secreting viscus, that in many of
them it can be instantly known and distinguished
at first sight from all other kinds or species of
flesh (§ 27).
§ 475.
It is also an opinion extremely probable (in
support of which we have advanced, on former
occasions, 

99 OF SECRETION. 
occasions, several arguments not easily refuted),
that the secreting viscera, besides their peculiar
parenchyma, possess also what we have taken the
liberty to call a vita propria, i. e. a specific or
exclusive kind of vital energy, essentially different
from what we denominated the three common
energies, namely, contractility, irritability, and sen-
sibility.
§ 476.
But further, if my views of the subject be in
any measure just, the absorbent system appears to
contribute also a very important part towards the
promotion of the several secretions: thus, from
each of the secreting viscera certain appropriate
branches of this system absorb and re-convey to
the blood-vessels larger or smaller portions of each
of the several humours to which these viscera give
origin; the uniform consequence of which is,
that the blood becomes literally impregnated with
the contagion of every humour secreted in the
different parts of the body, e. g. with bile from
the liver, with semen from the testes, &c.
Thus there appears to exist, in the system de-
stined for the business of secretion, a perpetual
routine or circulation, so that the elementary
parts of the humours already secreted being in-
cessantly conveyed from the secreting organs
G2 them- 

100 OF SECRETION.
themselves, are united afresh to the mass of blood,
and on their subsequent return to their parent
organs, in conjunction with the sanguineous cur-
rent, are again more easily attracted by the se-
creting vessels, in consequence of a peculiar law
of affinity, and have also a power of drawing
along with them those parts of the blood that
are most homogeneous in their nature, and for
which they consequently possess the highest de-
gree of attraction.
§ 477.
To facilitate the secretion of certain humours
of the body, adequate provision is made by the
production of specific qualities, in those particular
portions of the blood from which they are to be
proximately derived: thus the bile is secreted
from the blood of the vena portarum, a portion
of fluid highly impregnated with phlogiston, fur-
nished in profusion by the abdominal sources, from
which this blood immediately originates.
§ 478.
I pass in silence over certain other co-operating
aids, which act in subservience to particular secre-
tions, as congestion and derivation, so evidently
efficacious in the secretion of milk, with other in-
stances of a similar nature.
§ 479.

101 OF SECRETION.
§ 479.
Among the humours thus secreted by the or-
gans which we have just described, and by the
powers or causes just enumerated, it may be ob-
served that the following difference afterwards
exists, namely, while some of them drop imme-
diately from their secreting organs into the places
of their ultimate destination, in which they are to
perform their specific functions, others again are
conveyed to appropriated receptacles, in which
they are retained for some time, and thus farther
matured previously to their final elimination from
the system: of this last description is the milk
which stagnates in the lactiferous ducts, the urine,
the bile, and the semen masculinum, which are
subjected to retention in their vesicular receptacles,
and finally, the serum contained in those vesicles
which were first discovered by de Graaff in the
ovaria of the female.
G3 SECT. 

102 OF THE URINE.
SECT. XXXVIII.
OF THE URINE.
§ 480.
BESIDES the nutritious juices and the
secreted humours destined for further services in
the animal economy (§ 4.), the blood furnishes
also materials for the formation of certain useless
and superfluous liquids, that are intended to be
entirely eliminated from the system, and are from
thence vulgarly called excrements of the second di-
gestion. These excrementitious liquids are of two
kinds, one of which is exhaled by the process of
perspiration, and has already engaged our parti-
cular attention; the other is the urine, a liquid
secreted in those glands denominated kidneys.
§ 481.
The kidneys are two viscera situated behind the
peritoneum, on each side of the spine, and in the
upper part of the lumbar region: Although their
figure is generally somewhat flatted, yet it is pro-
per to observe, that both in this respect, and also
in point of number, they are subject to more va-
rieties than any other viscus belonging to the hu-
man body: they hang by vessels commonly called
emulgents

 

103 OF THE URINE. 
emulgents (remarkably large in proportion to the
magnitude of the parts on which they are distri-
buted), and are cushioned round by fat of a seba-
ceous consistence (§ 38).
§ 482.
They are invested by a proper membrane, of
an elegant vascular structure: each one of them,
especially during the period of infancy, appears to
be composed of about eight, or somewhat more,
kidney-form lobes or subdivisions; each of which
consists again (according to an opinion formerly en-
tertained and taught by Ferrein), of about seventy
or eighty fleshy radii, which that physiologist
called white pyramids.
§ 483.
If the kidney be dissected or divided from its
convex dorsum towards its concave pelvis, it ex-
hibits in its composition two kinds of substance;
one forming its circumference, and therefore de-
nominated its cortical, the other constituting its
centre, and hence called its medullary, portion.
Each portion abounds with sanguiferous arte-
ries and veins; besides which, the external cortex
is also furnished with an additional order of very
minute colouriess vessels, destined to secrete the
urine: while the medulla contains also vessels of
G4 a similar 

104 OF THE URINE.
a similar description, intended to carry it onward
when secreted.
Those secretory ducts originate, in the manner
already described (§ 471.), from the small glo-
bular convolutions of capillary arteries that are
every where interspersed throughout the cortex
of the kidney: those ducts constitute indeed by
far the greater portion of the cortical substance
of the kidney, and may be very easily distinguished
by their singular meanderings and intricate mazes,
from the small conducting tubes of Bellini, in which
they finally terminate. These tubuli Belliniani
(as they are frequently termed) pass by a direct
route from the cortical, and enter the medullary
substance, of which they constitute by far the
greater part; and uniting afterwards by reiterated
coalitions into a small number of narrow trunks,
finally perforate, by their extreme orifices, in a
sieve-like manner, the several papillæ contained in
the renal pelvis.
§ 484.
The papillæ correspond for the most part to the
number of lobes, of which we already said each
kidney is composed. The urine that is secreted
in the colourless vessels of the cortex, and after-
wards conducted through the tubuli Belliniani of
the medulla, these papillæ discharge into their
corresponding 



105 OF THE URINE. 
corresponding infundibula, which form by their
subsequent confluence the common pelvis.
§ 485.
The pelvis is continued into the ureters, which
are membranous canals, exquisitely sensible, and
defended internally by a complete investiture or
lining of mucus; they are capable of extreme di-
latation; in man they are here and there uneven
in the width of their cavities, and are at length
inserted into the posterior surface, not far from
the neck of the urinary bladder. This insertion
is effected in such a manner, that the ureters do
not immediately perforate the parietes of the uri-
nary cyst, but descend a short distance between
its muscular and nervous coats (which are here
possessed of more than ordinary thickness), and
open finally into the cavity of this organ by ob-
lique orifices. By means of this structure, ade-
quate provision is made to prevent the urine, that
has once entered the cavity of the bladder, from
being forced to return again into the ureters by
an inverted or retrograde motion.
§ 486.
In an adult subject, the urinary bladder is in
general sufficiently capacious to contain about two
pounds of urine; its fundus or bottom, which in
the fætal state terminates in the urachus, and also
its 

106 OF THE URINE.
its posterior side, are invested by the peritoneum;
as to its remaining membranes or coats, they bear
a general resemblance to those of the stomach, of
which we have already spoken.
The muscular coat consists indeed of interrupted
bands of fleshy fibres, that surround the cyst,
forming at the same time various irregular decus-
sations or interfections, which are different in dif-
ferent subjects: this muscular coat physiologists
denominated detrusor urinæ, while they designate
by the name of sphincter vesicæ, those orbicular
fibres that partially surround the neck of the blad-
der, though they are very inconstant and irregu-
lar, both with respect to their figure and origin.
The nervous coat bestows on this membranous
viscus also the principal part of its strength and
firmness.
Finally, the internal coat, which is considered
by physiologists as a process or continuation of the
epidermis, is defended by a complete covering of
mucus, especially round the neck of the bladder.
§ 487.
Besides those public and well known routes of
the urine, of which we have already spoken, it
appears probable from several phenomena, that
there 

107 OF THE URINE.
there exist also certain secret avenues, which lead
immediately from the intestines to the uropoietic
organs. For the speedy discharge of certain
drinks from the urinary emunctory, so frequently
imbued with the odour, tinctured with the colour,
and characterized by other specific qualities of the
aliments recently taken in, will scarcely admit the
belief, that these liquids had performed, in so short
a time, the customary long and circuitous route
through the thoracic duct and sanguiferous sys-
tem: to the foregoing circumstance we may add
an account we have read, of the urine having
been found covered with oil, that entered into the
composition of an enema, which had been previ-
ously and recently thrown into the intestinum rec-
tum. It is, on the other hand, a circumstance
well known to physiologists of the present day,
that very striking and numerous anastomoses oc-
cur between the lymphatic vessels of the intes-
tines, and those of the kidneys. Lastly, it is now
unequivocally ascertained and confirmed by live
dissections, that if both ureters of a dog be tightly
enclosed in ligatures, and his bladder perfectly
evacuated of its contents, this latter organ will,
notwithstanding, in the term of three hours after-
wards, contain a certain quantity of urine; while
at the same time the usual avenues of this fluid,
namely, the ureters, are completely obstructed, as
is evident from this circumstance, that above the
ligatures

 

108 OF THE URINE.
ligatures these tubes suffer vast distention from the
accumulated urine.
§ 488.
But through whatever avenues the urine has
been conveyed to the bladder, its gradual accu-
mulation in that organ excites an uneasy sensation,
which becoming urgent and troublesome (§ 331.)
potently solicits its final elimination, through an
emissary or fewer destined for that particular pur-
pose, namely, the urethra. This excretory canal
is subjected to a variety in its conformation, found-
ed on the diversity of the sexes, of which we will
speak more amply when treating professedly of
the sexual functions.
§ 489.
In order to evacuate the bladder, it is necessary
to overcome the contraction of its sphincter, by
the exertion of its own detrusor (of which we for-
merly spoke) (§ 486.), aided by the co-operation
of the abdominal muscles, and those subservient
to the process of respiration; to which, in males
of the human species, we may add, lastly, the
action of the musculi acceleratores, which forcibly
ejaculate, per saltum, as it were, even the residuary
drops of urine that may be occasionally lodged in
the bulb of the urethra.
§ 490.


109 OF URINE.
§ 490.
As to the nature of the urine itself, it is subject
indeed, to an infinitude of varieties generated by
the circumstances of age, and season, but, above
all, by the longer or shorter term of time, subse-
quent to the previous use of food and drink, the
discharge of this fluid occurs; to which may be
also added, the quality of the aliment previously
used, &c. In general, however, when we exa-
mine the urine which is discharged by a healthy
human adult, immediately after sound and tran-
quil sleep, we discover it to be a watery liquid, of
a nidorous smell, and citron colour, containing in
its aqueous medium, (as in a common vehicle)
various elementary substances, especially earthy
and saline, which bear different proportions to
each other in different individuals, and even in
the same individual at different times and under
the influence of different circumstances. Of the
terrene elements the most abundant is, in general,
calcareous earth, which is not unfrequently sound
in the urinary passages under the form of calculi,
but which is, notwithstanding, extremely variable
and inconstant in its quantity. Of all the saline
matters, that most worthy of being mentioned, is
the essential and native salt of urine—called also,
microcosmic salt, fusible salt, &c. This saline sub-
stance contains, in a greater proportion than any
other


110 OF SEXUAL DISCRIMINATION.
other part of the human body, the celebrated
phosphoric acid chemically espoused to the volatile
alkali.
SECT. XXXIX.
OF THE DISCRIMINATION OF THE SEXES IN
GENERAL.
§ 491.
THOSE functions of the human body,
in the consideration of which we have been hi-
therto engaged, are indeed possessed, and exercised
in common, by the individuals of each sex: with
respect to the mode, however, in which some of
them are performed, there occur between the
two sexes no inconsiderable degrees of difference.
Of this difference, it may be proper briefly to
enumerate the leading points, previously to our
entrance on the consideration of what are denomi-
nated the sexual functions.
§ 492.
To speak, then, in general terms, each sex
possesses and exhibits its own peculiar habit, which
differs considerably from that of the other. In
the 

111 OF SEXUAL DISCRIMINATION. 
the human subject after birth, this difference of
habit is distinctly observable; but during the ten-
der fœtal state, is scarcely to be distinguished,
unless by more close and pointed attention;
neither indeed, in this state, can the external
organs of generation themselves be discriminated,
on a transient and superficial view, owing to the
extraordinary magnitude and prominency of the
female clitoris, and the very diminutive size of the
male scrotum.
§ 493.
During the period of infancy this difference of
the general habit, depending on the diversity of
sex, makes only a slight impression on the ob-
server; but becomes gradually more and more
obvious and striking till the full completion of the
years of puberty, at which period, the general
conformation of the female body, its tenderness,
its softness, and the usual inferiority of its stature,
contrasted with the athletic and robust body of
the male, exhibit this general habitual difference
in the most striking point of view.
§ 494.
Similar to the difference that occurs between
the external habits of body, that characterise the
two sexes, is that which is observable in the bones
them-

112 OF SEXUAL DISCRIMINATION.
themselves. These solid portions (all other cir-
cumstances being alike) are evidently much more
smooth and round in females than in males; the
cylindrical bones, in particular, are more slender
and delicate, and the plane ones more attenuated
or thin, in the former, than in the latter sex; not
to mention the peculiar diversities of certain re-
markable bones, particularly those of the thorax
and pelvis, with the clavicles, the femora, &c.
§ 495.
With respect to the soft parts of the body, we
may observe in general, that in females, the cel-
lular membrane is more lax, more pliable, and
consequently more readily dilatable in the state of
pregnancy: while the skin is more tender, fair
and beautiful, in consequence of the immediate
substratum of fat.
The hair of the head is generally of a greater
length in females than in males, while at the same
time, certain other parts of the body which in the
latter are rough and hairy, are in the former
either perfectly smooth, as the chin and breast;
less hairy, as the perineum; or planted with only
a very tender and soft down, as the arms and
legs.
4 § 496.

113 OF SEXUAL DISCRIMINATION. 
§ 496.
When speaking of the diversities of particular
functions, we must not silently pretermit the pulse,
which (other circumstances being alike) is more
frequent in females than in males, (§ 109). In
the former, the thorax is subjected to a greater
degree of motion, (especially at its superior part,)
than in the latter; the os hyoides is much smaller,
the larynx is less capacious, and hence the voice
more shrill.
§ 497.
With regard to the animal functions, it is ne-
cessary to observe in general, that in females the
mobility of the nervous system is much greater
than in males, the irritability is more exquisite;
and the propensity to commotions of the mind,
more prompt and spontaneous.
§ 498.
As to the natural functions, the appetite for
food is weaker in the female, than in the male
sex; while, on the other hand, the increase of the
body is more rapid in the former, and the state of
puberty and mature growth attained at an earlier
period.
VOL. II. H § 499.
 


114 OF THE GENITAL FUNCTION
§ 499.
But by far the greatest and most important
distinction of the sexes is derived from the genital
functions themselves, the male being furnished
with a power of fœcundation, and the female with
that of conception. A farther investigation of these
powers shall engage the greater part of our atten-
tion, throughout the remaining pages of this
work.
SECT. XL.
OF THE GENITAL FUNCTION OF THE MALE SEX.
§ 500.
THE genital liquor of the male is
prepared by the testes, two bodies suspended in
the scrotum by their spermatic cords, and (besides
the lymphatic veins with which they abound in
profusion), composed chiefly of three kinds of
vessels.
These are first, the spermatic artery, which in
proportion to its slender diameter is said to be the
longest of all the arteries belonging to the human
body:

115 OF THE MALE SEX. 
body: it in general conveys the blood immedi-
ately from the abdominal portion of the aorta
itself, to the body of the testis.
Secondly, the ductus deferens, which carries to
the visiculæ seminales, the semen when once se-
creted from the arterial blood.
And, lastly, what is commonly denominated the
pampiniform plexus of veins, the function of which
is to receive and convey to the cava or emulgent
vein, the blood that remains after the process of
secretion is accomplished.
§ 501.
The testes are not, from the time of their
earliest formation, suspended in the scrotum, as
represented in the above description: thus in the
male fœtus, while yet in a very tender and imma-
ture state, those glandular bodies occupy indeed
a very different situation, the reason and successive
changes of which were first accurately investigated
and detailed by Haller, at Gottengen in the year
1749, but were afterwards explained by other
writers on principles so different from each other,
as to have given rise to various controversies of
some weight and importance. Of the situation
and changes of the testes in the fœtal state, I am
prepared to lay before the reader a brief, though
H2 compre- 

116 OF THE GENITAL FUNCTION
comprehensive account,—the spontaneous result
of numerous observations made on nature herself,
during a remarkable series of dissections of male
embryo's, in which I engaged for the express
purpose of shedding light on this subject so inte-
resting to physiologists.
§ 502.
On opening the lower abdominal region of an
immature fœtus, we discover in each groin, near
what is called the ring of the oblique muscles, a
very narrow orifice in the membrane denominated
peritoneum; this orifice is the threshold to a strait
avenue or alley, as it were, that leads through the
abdominal ring itself, and terminates afterwards
in a peculiar bullous or bubble like sack: this
sack extends without the abdominal cavity, looks
towards the scrotum, is interwoven with cellular
fibres, and destined for the future reception of
the testis.
§ 503.
At the very posterior margin of this small
abdominal orifice, the peritoneum sends off an-
other process, which mounts upwards, and in the
tender fœtus represents, in the greater part of its
course, a longitudinal fold: from the basis of this
process a slender cylinder, or rather inverted cone
ascends, and forms at its summit, which regards
the

117 OF THE MALE SEX. 
the inferior margin of the kidney, a small blister
or sack-like termination; in this sack the testis
and epididymis are enclosed; so as to resemble,
at first sight, a small berry resting on its footstalk,
and appear, at the same time, to hang loosely into
the abdominal cavity somewhat like the liver or
spleen (§ 404).
§ 504.
The vessels which are afterwards to constitute
the spermatic cord, are, at this very early period,
seen running behind the extremely tender and
pellucid peritoneum, so that the spermatic artery
and vein run in a descending direction along the
sides of the spine, while the vas deferens bending
somewhat inwardly towards the neck of the uri-
nary bladder, stretches along the loose cellular
membrane, which is situated behind the perito-
neum, and both enter the body of the testis in
that peritoneal plica or fold of which we have
already spoken.
§ 505.
From about the middle stage of pregnancy, the
testes begin to sink downward by degrees, so as
gradually to approach the narrow orifice of the
peritoneum, which has been already mentioned.
At the same time, the foregoing peritoneal fold,
with its cylindrical attachment, are wrapped up
H3 by 


118 OF THE GENITAL FUNCTION
by degrees, till the testis finally rests on the very
mouth of the preceding canal.
§ 506.
When in the fœtus, now advanced to a higher
stage of maturity, the testis is fully prepared for
a final descent, the orifice, hitherto so contracted
or narrow, suffers such a remarkable dilatation,
that the testis is at full liberty to enter with facility
the opening that leads out of the abdomen as well
as the ring by which this opening is surrounded,
to pass onward through the whole length of the
canal, and thus plunge headlong, as it were, into
the blister-like sac of which we have already spo-
ken. The testis having finally accomplished its
descent, the peritoneal opening is soon after closed
in the most complete manner, and even subjected
in a short time to a perfect adhesion of its sides, so
that in the stage of infancy, scarcely a wreck of
it is left, to point the enquirer to the place of its
former existence.
§ 507.
The more gradual and slow the movement of
the testis (while yet in the abdominal cavity) to-
wards the orifice of its egression, the more sud-
den and instantaneous appears to be its act of
transition through the abdominal ring. For in
the dissections of mature fœtuses, it is by no means
uncom-



119 OF THE MALE SEX.
uncommon to discover the testis either as yet in-
cumbent on the peritoneal opening, or else statio-
nary in the groin, after having recently passed the
abdominal ring: but once only was I so fortunate
as to have an opportunity of observing the right
testicle of a twin-fœtus (of which a complete
drawing has been given), at the very moment of
its passage through the abdominal ring: the gland
appeared to have been very tightly embraced and
strangled, as it were, by the surrounding parts,
and was apparently in complete readiness to
emerge from the abdomen into its destined sack;
a transition already accomplished by the left tes-
ticle, that had just escaped from the ring, the ori-
fice of which had again resumed its former imper-
vious state.
§ 508.
This remarkable descent of the testes along the
groins, does not appear to be exclusively confined
to any particular period of time: it occurs for
the most part, however, about the last month of
pregnancy: although these glandular bodies are
not unfrequently found either in the abdominal
cavity itself, or in the superior part of their in-
guinal route, even in infants after birth. For the
testicle, after its entire escape from the abdomen,
has still a further stage of its journey to perform,
namely, its final descent along the groin into the
H4 scrotum, 



120 OF THE GENITAL FUNCTION
scrotum, in company with the small sac by which
it is enveloped.
§ 509.
That the foregoing is indeed a true account of
the progressive movement of the testes in their
descent from the abdomen into the scrotum, I
have had sufficient opportunities of ascertaining
from repeated observation. To develope the
causes and energies by which this astonishing de-
scent is accomplished, appears to be indeed attend-
ed with difficulties of the utmost magnitude. For I
am daily more and more convinced, that neither of
those powers to which this descent has been hither-
to ascribed (such, for example, as the action of the
cremaster muscle, the action of the diaphragm, or
the contractility alone of that cellular and tendi-
nous intertexture, which adheres to the processes
of the peritoneum, and is usually denominated
gubernaculum Hunterii, &c.), is sufficient to ex-
plain a movement of such extreme singularity,
especially that part of it relating to the immediate
transition of the testis through the narrow abdo-
minal ring, to which the reader's attention has
been so frequently solicited: while I am impressed,
on the other hand, by a thorough conviction,
that this whole process exhibits the most unequi-
vocal and striking example of what we have de-
nominated specific life, without the peculiar opera-
tion

 

121 OF THE MALE SEX.
tion and aid of which, it is scarcely possible to
solve the several phenomena of a transition so ex-
tremely singular in its nature, and so widely dissi-
milar to all other movements and functions that
occur in the whole animal economy.
§ 510.
The involucra by which the testes are invested,
after their final completion of the foregoing route,
may be aptly enough divided into common and
proper.
The only involucrum common to both these
glandular bodies is the scrotum. This is a sac,
consisting of a tender portion of cutis expanded
over a thin substratum of fat, and possessing a pe-
culiarity that does not reside in any other part of
the common integuments of the body, namely, a
power of changing, in a very remarkable degree,
its usual habit and appearance: thus, it sometimes
depends loose and flaccid, and again (especially
under the impression of the venereal œstrum, or
in case of exposure to cold), becomes constricted
and rigid, as it were, and is then particularly
marked by furrows and diversified rugosities.
§ 511.
Of those involucra which are proper to each
testis, that placed immediately beneath and within
the 

122 OF THE GENITAL FUNCTION
the scrotum, is called the tunica dartos: this coat
possesses a very peculiar and vivid contractility, by
which Winslow, Haller, and other celebrated cha-
racters have been so far deceived, as to bestow on
it the nature and energy of a muscle.
§ 512.
This is succeeded (after a voluminous and soft
stratum of cellular membrane), by three separate
vaginal coverings, which were first accurately
traced and distinguished by the ingenious and in-
defatigable Neubauer.
Of these vaginal coats, the exterior is common
to the testicle and spermatic cord, and has the cre-
master muscle attached to it by separate bundles
of fibres.
But the two interior are proper, one to the sper-
matic cord, and the other to the testis itself; of
these the latter adheres, for the most part, by its
fundus to the common tunic, while its internal
surface is moistened by a lubricant fluid, some-
what after the manner of the pericardium.
§ 513.
The origin of those vaginal tunics which has
given rise to such a variety of controversies among
physiologists, can, (if I be not greatly deceived),
be 
 

123 OF THE MALE SEX. 
be without difficulty ascertained, from what has
been already said, when treating of the descent of
the testes.
Thus, the tunica communis, for example, origi-
nates from the descending (§ 502.) blister-like
sac or process of the peritoneum.
The propria testis, from that production of the
peritoneum, which mounting upward in the form
of a cylinder (§ 503.), invests the testis itself from
its earliest formation.
And, finally, the propria funiculi, from that
fold of the peritoneum, of which we have already
spoken, and the short cylinder in which it termi-
nates previously to its embracing the testis itself.
§ 514.
Immediately to the testis itself the tunica albu-
ginea is very closely attached, somewhat after the
manner of a cortical covering. From this tunic,
blood-vessels pass into the pulp or body of the
testicle, which consists indeed entirely of innume-
rable vessels, about a span in length, wound up
into small conglomerate lobules: these vessels, of
which the substance of the testicle is composed,
are both sanguiferous and secreting, the latter of
which 

124 OF THE GENITAL FUNCTION
which conduct the semen, when prepared, through
the vascular net-work of Haller, and the vasa
defferentia of Graaf, into the beginnings of those
cones that form the epididymis.
§ 515.
That body which ranges along the side of the
testis, namely, the epididymis, consists indeed of a
single vessel, about thirty feet in length, which at
one end (that for instance denominated its head),
is distinguished into about twenty small rolls or
cones, and at its other (inferior) extremity, called
therefore its tail, increases gradually in thickness,
and thus forms by its continuation the vas de-
ferens.
§ 516.
The two vasa deferentia ascending towards the
neck of the urinary bladder, and forming a junc-
tion beneath, or near to, the prostate gland, are
from hence bent backward, and expanded into
the vesiculæ seminales; in such a manner, how-
ever, that these vesiculæ, and the vasa deferentia
themselves, open by two common orifices into the
urethra, just behind the caput gallinaginis.
§ 517.
Finally, the vesiculæ seminales themselves, are
attached to the posterior surface of the urinary
cyst, 


125 OF THE MALE SEX. 
cyst, near to the inferior extremity, or neck, of
that organ: they are imbedded in a profuse quan-
tity of fat, and from their diversified flexuosities
and numerous blind appendiculæ that shoot oft
somewhat in the form of ramifications, resemble,
in their general appearance, two small intestines.
These vesiculæ consist of two coats, almost of
the same kind with those that enter, as formerly
mentioned, into the composition of the gall blad-
der; thus, the first or external coat is more ro-
bust, and similar in its nature to such as are com-
monly denominated nervous; while the second or
internal abounds with minute cells and pits, and
is every where divided, by means of projecting
eminences, into minute purse-like cavities, per-
fectly similar to those that are so conspicuous
about the neck of the gall-bladder.
§ 518.
In those organs and vessels hitherto enume-
rated and described, there is, even from the ear-
liest years of puberty, a certain fluid secreted
slowly, and retained in small quantity, namely,
the semen masculinum; a liquor extremely singular
in its nature, and of the utmost dignity and im-
portance in the animal economy: it exhibits to
the eye a milky colour, emits an odour entirely
peculiar, possesses a mucoid viscosity, and is of
such


126 OF THE GENITAL FUNCTION
such remarkable specific gravity, as to surpass, in
this respect, all other secreted humours belonging
to the animal body.
§ 519.
A peculiarity of this fluid, which must not be
passed over in silence, is, (as was first observed by
Lud. Ham at Dantzic, in the year 1677), that it
is peopled by a countless multitude of microscopic
animalculæ, belonging to the same order with
those called infusoria, and possessing different
figures, as they appear in the seminal fluids of dif-
ferent animals. In man (and also in the male
ass) the seminal animalcules exhibit oval figures,
furnished with tails of extreme minuteness: these
animalcules are said not to be found in any, save
found and prolific semen, so that they appear to
constitute a certain adventitious criterion of the
fertilizing maturity of this important fluid: we
have called the criterion derived from these ani-
malcules adventitious, and presume it is scarcely
necessary, at this enlightened period, to repeat,
that they should not be accounted the reservoirs
of the secundating principle, much less should they
be considered as the germs of future homunculi,
since so many, and such weighty arguments and
observations have been lately advanced in sup-
port of a different doctrine.
§ 520.


127 OF THE MALE SEX. 
§ 520. 
This genital liquid being gradually collected in
the vesiculæ, which we have already described, is
there retained till a future act of excretion. By
such retention it suffers changes very nearly re-
sembling those to which the bile is subjected in
consequence of a state of stagnancy in its cystic
reservoir; thus, being gradually robbed of its
aqueous portion, it is more and more inspissated
and approximated, as it were, towards a state of
concentration.
§ 521.
For as the testes generally, together with the
cords by which they are suspended, abound with
an astonishing assemblage of lymphatic vessels,
which serve to re-convey from thence to the
blood a portion of fluid, impregnated with the
spermatic contagion, and by this means aid and
facilitate the further secretion of semen, on the
principle, and in the manner formerly laid down
(§ 476.), so are the vesiculæ seminales themselves
also provided with vessels of the same kind, which
by absorbing the subtle, though inert water, ren-
der the residue of the seminal fluid more active
and efficacious.
§ 522.
 

128 OF THE GENITAL FUNCTION
§ 522.
On this subject I doubt much whether or not,
in a healthy man, any genuine semen be ever ab-
sorbed from the vesiculæ seminales:—more still,
whether or not, as is sometimes alleged, semen
thus absorbed could be carried immediately into
the neighbouring sanguiferous veins:—but most
of all, whether or not such a seminal absorption
(admitting its real existence) could possibly act as
an antidote against excessive venereal propensities,
since it appears evidently, on the other hand, that
this same absorption would necessarily operate as
an exciting cause of unbridled and almost infuriate
lust: in quest of testimony to establish the truth of
this latter proposition, we need only attend to the
phenomena of such animals as experience the ve-
nereal propensity only at stated seasons of the
year, and compare them with the constitution of
those that have been reduced to the state of cas-
tration.
§ 523.
To me indeed it appears probable, that, for the
purpose of moderating libidinous desires, man is
endowed with a far different prerogative (not
conferred on any other species of animals with
which we are hitherto acquainted), namely, that
of nocturnal pollutions: these evacuations I there-
fore consider among the natural excretions of man
I —evacua- 



129 OF THE MALE SEX. 
—evacuations by which (as they occur at longer
or shorter intervals, according to the varieties of
temperament and constitution), he is relieved from
a troublesome and otherwise urgent impression
produced by an abundant accumulation of semen.
§ 524.
It must be observed, however, that the semen
masculinum is never excreted in a state of entire
purity, but is always blended with more or less of
what is usually denominated liquor prostatæ (i. e.
the liquor of the prostate). With regard to the
external habit and appearance of this last men-
tioned liquid, it bears a very striking similitude to
the albumen or white of eggs. This peculiar
liquor derives its name from its immediate birth-
place or source, which is a body of considerable
magnitude, and of a singular and very compact
parenchymatous texture, situated between the ve-
siculæ seminales and the bulb of the urethra, and
is usually designated by the name of glandula pro-
stata. The excretory avenues of this liquor have
not yet been satisfactorily investigated and ascer-
tained, unless (as appears probable) they commu-
nicate with the duct of the caruncula seminalis,
the orifice of which opens into the urethra be-
tween the two mouths of the avenues leading
from those minute vesicles destined for the recep- 
VOL. II. I tion


130 OF THE GENITAL FUNCTION
tion and temporary retention of the fertilizing
semen, (§ 516).
§ 525.
The urethra in man is destined as a common
conduit or emissary duct, to three different kinds
of fluids, namely, the urine, the semen, and the
liquor of the prostate gland. It is lined internally
with a mucus which originates from an immense
number of sinuses, that are every where dispersed
throughout its canal. It is surrounded by a sub-
stance of a spongy texture, to which are subjoined
two other bodies, similar in structure but far supe-
rior in size, (called corpora cavernosa), that con-
stitute the principal part of the male penis; an
organ which is terminated anteriorly by the glans,
and wholly invested by a very tender and pliable
portion of skin entirely destitute of all appearance
of fat. This skin forms the prepuce by its at-
tachment round the corona, or circular base of the
glans, and plays over this body with a free motion,
somewhat like the palpebræ over the ball of the
eye. The interior duplicature of the prepuce,
having assumed a different appearance, is reflected
over the glans itself, (somewhat like the adnata
over the eye) and is furnished around the corona,
with an immense number of the small glands of
Littrius, (analogous to the Meibomian glands of
the 


131 OF THE MALE SEX. 
the palpebræ) that give birth to a matter of an
unctuous but very singular nature.
§ 526.
The male penis, thus organised and constructed
agreeably to the preceding description, possesses a
faculty of erection, i. e. in consequence of an
encreased congestion and impetuous effusion (for
congestion alone will not explain the phenomenon)
of blood into the corpora cavernosa, the penis
swells, becomes rigid, and changes its former
position, but suffers again a detumescence and
collapse by a reabsorption of the superfluous por-
tion of this distending fluid. 
§ 527.
When the penis resumes its flaccid condition,
it suffers a singularly circuitous flexion, at the
place where it originates from the neck of the
bladder. In this state it is, indeed, extremely
well calculated for the excretion of real urine, but
quite unqualified for the emission of semen, as the
beginning of the urethra forms now a more acute
angle with the small orifices of the vesiculæ semi-
nales.
§ 528. 
When a gradual intumescence of the penis com-
mences, there occurs first an effusion of the liquor
I2 furnished 


132 OF THE GENITAL FUNCTION, &c.
furnished by the prostate gland, which is often-
times eliminated unmixed, but scarely ever along
with the urine. Of this liquor the primary desti-
nation is, to be ejected, in conjunction with the
seminal fluid itself; either, that it may, by its
albuminoid lubricity, qualify the sluggish tenacity
of the latter fluid, and thus facilitate and promote
its ejection; or that it may itself contribute, in a
certain degree, towards the process of generation.
§ 529.
The emission itself of the male semen is excited
as well by the immediate impression arising from
an abundant accumulation of this fluid in its ap-
propriated receptacles, as by the genuine sexual
instinct; it is accomplished, first, by a very strong
erection of the penis, which, while it obstructs the
passage of the urine, paves as it were, on the
other hand, a more direct and ready way for the
transition of the semen; to which we may subjoin,
as co-operating causes, a certain spasmodic con-
traction of the vesiculæ seminales, a convulsive
action of the levator ani, and acceleratores urinæ,
and finally, a general succession, of the whole ner-
vous system, gentle indeed in degree, and transient
in existence, but yet of an epileptic nature, and
considerably depressing, in its effects, on the ener-
gies of the system.
SECT. 




133 OF THE GENITAL FUNCTION, &c. 
SECT. XLI.
OF THE GENITAL FUNCTION OF THE FEMALE SEX
IN GENERAL.
§ 530.
AS the male organs of generation are
naturally calculated to give, so are the female to
receive, and in the two sexes these organs are, in
a general point of view, widely different from
each other. It must be observed, however, that
in the general structure of certain parts, these two
kinds of organs exhibit no small degree of reci-
procal similitude. Thus beneath the pubes (the
structure of which has been already a subject of
transient attention (§ 36.) the clitoris which lies
concealed in the superior commissure of the labia,
resembles the male penis in more respects than
one, but is not furnished with a urethra, is there-
fore imperforate, and, (when not of a preter-
natural proportion,) is remarkably small. It is
said, however, that this organ preserves, occasion-
ally, even in adults, the same proportional size,
which, as formerly observed, is so extremely
conspicuous in the clitoris of the female embryo,
(§ 492.) Hence appears, in all probability, to
have originated most of those obscene and fabulous
I3 stories, 



134 OF THE GENITAL FUNCTION
stories, respecting the existence of hermaphrodites.
This organ consists also, like the male penis, of
corpora cavernosa, like it, is capable of erection,
like it, is invested by a prepuce, and furnishes,
finally, an unctuous matter not dissimilar to that
of Littrius, (§ 525).
§ 531.
From the clitoris descend the nymphæ, acquiring,
also, occasionally, an enormous and preternatural
magnitude, (which excess has, in like manner, not
unfrequently given rise to extraordinary and fabu-
lous reports): they possess, in common with the
clitoris the most exquisite degree of sensibility;
and appear to give direction to the stream of urine
when discharged, as the orifice of the urethra,
(a tube extremely short in the female sex, and, in
the most highly finished and perfect examples,
ciliated or fringed in a very singular manner), lies
hid, as it were, in a fossa formed by their two
bases.
§ 532.
Beneath this orifice is situated the opening of
the vagina itself, environed by cryptæ of various
kinds, such, for example, as the urethral lacunæ
of Graaf, and the mouths of what are improperly
and even absurdly termed, the prostate glands of
Casp. Bartholin, &c. with the unguen-like mucus
of 

 

135 OF THE FEMALE SEX. 
of which, these obscene parts are moistened and
lubricated.
§ 533.
Over the very threshold or entrance of the
vagina is expanded a weblike production denomi-
nated the hymen. This is a membrane, the exis-
tence of which in an unlacerated condition, is
considered as a sure badge of spotless virginity—
a membrane bestowed exclusively on the female
of the human species, and of which no physical
destination has been yet unequivocally ascertained.
The fringes or residual fragments of this mem-
brane, after laceration, are gradually converted
into what are denominated carunculæ myrtiformes,
bodies quite indefinite in point of number.
§ 534.
From the immediate seat of these minute myrti-
form bodies ascends, between the urinary cyst and
intestinum rectum, the vagina, a tube composed
of a cellular parenchyma, interspersed with an
infinitude of small blood-vessels. At its inferior
extremity the vagina is encircled by a muscle
denominated constrictor cunni; more internally it
is lined by a very soft and delicate coat, which is
characterised by two extremely elegant columns of
rugæ or wrinkles, namely, the anterior and poste-
I4 rior;

136 OF THE GENITAL FUNCTION
rior; from these columns a fine mucus is con-
stantly discharged, destined to lubricate the cavity
of this highly important canal.
§ 535.
The vagina, at its upper and interior end, re-
ceives and embraces, finally, the uterus, an organ
attached on each side to, and thus suspended by,
the ligamenta lata.
The cylindrical neck of this organ being thus
embraced, as it were, by the vagina, is perforated
by a narrow canal, which, like that of the vagina,
is impressed by a singular apparatus or arrange-
ment of rugosities, designated by the name of
arbor vitæ: of this canal the two extreme orifices,
more especially the superior or internal, are over-
spread, for the most part, with a quantity of tena-
cious mucus.
§ 536.
The substance of the uterus is altogether sin-
gular in its nature, consisting of a peculiar paren-
chyma, very dense and compact, and interwoven
with an infinitude of blood-vessels (running in
serpentine mazes of astonishing intricacy) of which,
the veins are wholly destitute of valves. This
organ is doubtless furnished, in like manner, with
an apparatus of lymphatic vessels: it abounds
with 

137 OF THE FEMALE SEX. 
with a countless number of nerves, through the
medium of which, it preserves such an astonishing
sympathy with the other parts of the system.
§ 537.
Externally the uterus is invested by the perito-
neum, while its minute internal cavity is lined,
especially at its fundus, by a very soft and tender
membrane, of a spongy texture, which, as some
physiologists allege, consists of colourless vessels,
while others pronounce it to be composed of lym-
phatic absorbents.
§ 538. 
With regard to the muscular texture attributed
to this organ by some physiologists, and strenu-
ously denied again by others, I must take the
liberty of observing, that notwithstanding the
number of uteri which I have examined with the
utmost care and attention, both in an impregnated
and an unimpregnated state, (in each of which I
have had repeated opportunities of examining this
organ, not only in a prepared condition, but also
in subjects recently dead), I have never yet been
able to detect, in them, any portion that exhibited
obvious and unequivocal signs of muscularity. On
the other hand, I am daily more and more per-
suaded, that the uterus, possessing no muscular
fibres, is destitute also of true irritability (§ 307),
and 



138 OF THE GENITAL FUNCTION
and owes entirely to a vita propria, or specific life
(§ 47.), all its peculiar motions and functions,
which cannot, indeed, with the smallest semblance
of propriety, be derived from any of those ener-
gies that are common to what we formerly term-
ed the partes similares, or similar parts of the
body (§ 43, 46). So very singular and unac-
countable did the motions and functions of the
uterus appear to the physicians and philosophers
of ancient times, that they were led to consider
this organ as a smaller animal contained within a
larger.
§ 539.
From the angles on each side of the lacunar,
or fundus uteri, arise what are called the Fallopian
tubes. These are two very narrow and tortuous
canals, that run in the superior duplicature of the
ligamenta lata: they are similar in texture to the
vagina itself, except, that being internally destitute
of valves, they are lined with a kind of spongy
flesh, of a very soft and tender consistence.
§ 540.
The extreme orifices of these tubes, that regard
the abdominal cavity, besides being much more
capacious than those which open into the uterus,
are also edged round by fringe or finger-like fim-
briæ, of a truly singular and elegant structure.
The 



139 OF THE FEMALE SEX. 
The offices which these fimbriæ are destined to
perform, in the business of conception, appear to
be indeed of no small degree of importance; thus
being rendered, during the venereal orgasm,
equally turgid with the tubes themselves, they
evidently embrace, in this state, the ovaria that
are situated in some measure beneath them.
§ 541.
The ovaria themselves, or the female testes, as
they were called previously to the time of Steno,
besides a tenacious and somewhat tendon-like in-
volucrum, consist also of a dense and decussating
cellular membrane, which incloses in each ova-
rium about fifteen of those minute bodies denomi-
nated the ovula, or little eggs of Graaf: these
ovula contain each a small vesicle, or rather drop
of serum, faintly yellowish in its colour, and of an
albuminous nature, which, if the recent ovarium
be immersed in boiling water, is reduced, like the
genuine white of eggs, to a state of complete co-
agulation.
§ 542.
An albuminoid drop of this kind appears to be
indeed the principal fluid which the female con-
tributes towards the process of conception; for it
appears extremely probable, that, throughout the
progressive course of what are termed the prime
or 


140 OF THE GENITAL FUNCTION, &c.
or better years of life, these small drops arrive at
complete maturity in gradual succession, so that
each one, in its turn, looks as it were through the
involucrum, by which the ovarium is enveloped,
till it is able finally to burst the parietes of its
prison, and thus be received by the abdominal
orifice of the Fallopian tube.
§ 543.
But besides this minute albuminous drop that
thus bursts from the volume of the ovarium, it
appears that there occurs also, during the vene-
real œstrum, an effusion of another liquor, which
ancient physiologists very improperly and errone-
ously denominated the female semen. Respecting
the nature, however, the sources, and the univer-
sal presence of this humour, we are able to pro-
pose nothing more determinate or satisfactory than
we can advance with regard to its destination
and uses.
SECT. 

141 OF MENSTRUATION.
SECT. XLII.
OF MENSTRUATION.
§ 544.
A VERY frequent and highly import-
ant function of the uterus in the female of the hu-
man species is, to discharge monthly a tributary
effusion (called therefore catamenia), during the
tedious and momentous term of about thirty years.
This is a painful condition of existence, to which
nature has not subjected any other genus of her
subjects, throughout the wide and diversified range
of the whole animal kingdom; so that to use the
words of the eloquent Pliny "the only menstruous
"animal in nature is woman." From this con-
dition, on the other hand, painful as it is, nature
has not exempted the females of any of the known
nations of the globe, but has stamped it with
the sacred character of an essential requisite—of
a genuine sine qua non, in rendering the female
sex competent to the propagation of their species.
§ 545. 
The commencement of this singular function
generally takes place, in our climate, about the
fifteenth year of life, and is, for the most part,
preceded by various and unequivocal symptoms
of 


142 OF MENSTRUATION.
of plethora, such as congestion and anxiety about
the breast, sense of tension and weight in the lum-
bar region, lassitude or weariness of the limbs, &c.
On the first appearance of the catamenia, the ge-
nital organs, in the beginning of the attack, usu-
ally discharge a humour of a pale reddish cast;
this is gradually succeeded by a liquid of a more
intensely florid and sanguineous colour, which
terminates, at length, in an effusion of genuine
cruor or red blood. This spontaneous, though
gentle discharge of blood, is kept up for the
term of several days, and is, in the mean time,
accompanied by a gradual cessation of all those
distressing symptoms of which we have just exhi-
bited a partial detail.
§ 546.
From the time of its first occurrence, this con-
stitutional hemorrhagy (as it may, with sufficient
propriety, be denominated) becomes regularly pe-
riodical: thus its future paroxysms return uni-
formly about the expiration of every fourth week,
and at each recurrence, the evacuation continues,
at a mean calculation, about six days; during
which term, a healthy female is supposed to dis-
charge from eight ounces to an entire pound of
blood.
§ 547. 

143 OF MENSTRUATION. 
§ 547.
It is proper, however, to observe, that this func-
tion is subject, for the most part, to an entire in-
termission, during the state of female pregnancy,
and the term of maternal lactation.
The final cessation of the catamenia occurs after
their discharge has continued, at stated periods,
about the space of thirty years, which term of
time is completed, in our climate, about the 45th
year of life.
§ 548.
The sources of the catamenial discharge have
been referred by some to the vessels of the vagina,
and by others (with superior weight of evidence
on their side) to those of the uterus: for with
regard to those examples commonly adduced in
support of the former opinion, where women,
although pregnant, possessing an imperforated
uterus, or distressed by a prolapsus of that organ
in an inverted state, have notwithstanding men-
struated with uniform regularity, they tend to
prove nothing else than the powerful efforts of
the vis medicatrix naturæ, which in cases where
the main street is obstructed, is (to adopt a vulgar
mode of expression) fortunately acquainted with
the routes through lanes and alleys. There are
on record, on the other hand, numerous dissections
of



144 OF MENSTRUATION.
of females who died during the term of actual
menstruation, from which it was unequivocally
ascertained, that the catamenial discharge had
been wept out of, or discharged in a stillicidious
manner from, the uterine cavity of these subjects:
not to mention the arguments drawn a priori (as
metaphysicians express themselves), from which it
appears highly probable, that the end and desti-
nation of the menses are, to prepare the uterus
for a state of future pregnancy, and render it more
fit for the regular nutrition of the fœtus. For
the very same reasons also this hemorrhagy ap-
pears to be attributed, with more propriety, to
the arterial than to the venous vessels of the
uterus.
§ 549.
With regard to the causes of this periodical and
perennial hemorrhagy, they are shrouded by so
thick a curtain of obscurity, and their investigation
is attended with such momentous difficulties, that
in the prosecution of this subject, we have not a
sufficient power of evidence to conduct us over
the arduous mound which divides the twilight-
region of probability from the more luminous realm
of demonstration, and certainty.
The proximate cause physiologists suppose to be
a certain topical congestion or plethora, to which
2 opinion,



145 OF MENSTRUATION. 
opinion, indeed, the symptoms of the impending
catamenia, together with the profusion and nature
of the uterine blood-vessels fitly enough correspond,
and in favour of the truth of which they exhibit
a degree of testimony sufficiently respectable.
Among its remote causes it will be proper to
enumerate, the erect position of the body (a posi-
tion that serves as a characteristic distinction be-
tween the human species and most other descrip-
tions of animals); to which we must add, the
singular parenchyma of the uterus itself, and,
finally, the vita propria or specific life of that
important organ. 
With regard to the cause of the periodical re-
currence of the catamenia, it will here be better,
much better to acknowledge our ignorance, than
to indulge ourselves in vague and visionary con-
jectures, and sportively range through the fair but
fallacious fields of mere speculative hypothesis.
For I am, indeed, persuaded, that all those peri-
odical phenomena which occur in the animal body,
whether in health or disease, (provided their in-
terval extend beyond the term of 24 hours) must
be ranked with those latent mysteries of animal
nature, which nothing but time, talents, and in-
dustry, will be ever able to develope.
VOL. II. K SECT. 



146 OF THE MILK.
SECT. XLIII.
OF THE MILK.
§ 55O.
BETWEEN the female mammæ and
uterus (the former of which were, by the philo-
sopher Favorinus in his communications to Gelllius,
elegantly and emphatically denominated, the sa-
cred fountains that nourish the human race, there
exists such an extremely potent sympathetic con-
nection, that these two organs may be said to be
indissolubly associated, or to accompany each other
hand in hand, in their phenomena and functions.
Thus, during the tender period of infancy, so
great is their imbecility and want of action, that
they are capable of performing scarcely any func-
tion at all: as the years of puberty advance,
they begin, at the same time, to acquire vigour
and activity, so that on the first eruption of the
catamenia, a swelling of the mammæ or breasts
becomes also evident to the senses. Throughout
the subsequent periods of life those two organs
are either subjected to simultaneous and similar
changes, as when the breasts become turgid and
discharge milk during the progress of pregnancy;
or experience alternate and opposite affections,
instances
 

147 OF THE MILK. 
instances of which we have in the suspension of
the catamenia during the term of lactation, a more
copious effusion of the lochia when the secretion
of milk does not commence at the usual period,
&c. And, lastly, on the unwelcome accession of
old age, both the preceding functions fail at the
same time, so that when the catamenia finally
retreat, never again to return, the uterus and
mammæ become equally flaccid, inert and wholly
incapable of their former action. A great variety
of pathological phenomena, easily observable in
cases of irregular menstruation, in fluor albus, and
other similar affections, shall be in silence preter-
mitted, although they furnish the most potent and
unequivocal testimony in confirmation of the
sympathy now under consideration, namely, that
which exists between the uterus and mammæ.
§ 551.
Nor will this intimate sympathetic connection,
which subsists between the uterus and mammæ,
appear in any measure extraordinary or surprising,
when we consider, that all those diversified sources
of physiological consent, particularly enumerated
on a former occasion (§ 54), jointly co-operate in
the establishment of such connection between these
organs of the female thorax and abdomen.
K2 § 552.

148 OF THE MILK.
§ 552.
The anastomosis observable between the internal
mammary and epigastric arteries, was formerly
esteemed a circumstance of the highest importance
in the explication of the foregoing consent. Al-
though physiologists have hitherto attributed by
far too much to this remarkable anastomosis, yet
that it ought not to be entirely excepted from the
number of co-operating causes will appear ex-
tremely probable to any one who considers the
obvious and wide difference which exists between
the diameter of the epigastric artery in a state of
pregnancy, and that of the same vessel during the
period of lactation.
§ 553.
The two preceding organs, namely, the uterus
and mammæ, possess also, in common with each
other, this further property, that they both retain
and exhibit a friendly affinity or attraction for the
chyle, by which means they solicit that fluid to
themselves, especially during the term of preg-
nancy, and thus convert it to peculiar uses.
§ 554.
The female mammæ consists of a placentoid con-
geries of small conglomerate glands, distinguished
by numerous sulci into lobes of considerable mag-
nitude, and completely embedded in a mass of
adipose 


 

149 OF THE MILK.
adipose substance. On the anterior part, in particu-
lar, a protuberance is formed by a more firm seba-
cious cushion, which is covered and protected by
a cutis of a very tender and delicate texture.
§ 555.
Each one of these lobes is composed of a num-
ber of inferior lobuli, and these again of what are
denominated acini or kernels, in which the incipi-
ent radicles of the lactiferous ducts originate, and
from the extreme ramuli or branches of the in-
ternal mammary artery extract a chyliform fluid,
which they are particularly destined to convey.
§ 556.
The fine filiform radicles uniting successively
in their onward passage, terminate finally in lead-
ing trunks, corresponding in number to the prin-
cipal lobes; so that they generally amount, in
each mamma, to about fifteen or perhaps a few
more. These trunks are frequently dilated into
more spacious sinuses, but never appear to be con-
nected by genuine anastomoses.
§ 557.
These trunks terminate in excretory canals of
exquisite delicacy and tenderness, which, bein 
collected and closely approximated towards the
centre of the mamma, form, by the co-opera
K3 
 

150 OF THE MILK.
of cellular membrane, the papilla or nipple. This
projecting papilla being interspersed and minutely
pervaded by an infinitude of blood-vessels and
nerves of extreme fineness and subtlety, is subject
to a very singular species of erection on the acces-
sion of certain external stimuli.
§ 558.
The nipple is surrounded by an areola or small
circle, which is conspicuous, as well as the pa-
pilla itself, on account of the singular colour of
the reticulum mucosum expanded immediately be-
neath the epidermis or cuticle. This areola is
further distinguished by small sebaceous follicles,
and likewise by a few minute lactiferous ducts with
which it is in some instances pervaded.
§ 559.
The human milk which is secreted in the glan-
dular organs hitherto described, is a fluid of a
well known colour, somewhat watery, and con-
taining also a small portion of oil: this liquid is
sweetish to the taste, extremely mild, and resem-
bles, in its general properties, the milk of do-
mestic animals belonging to the class mammalia,
except that it is not, like the latter, subject to co-
agulation from the action of acids, nor does it ex-
hibit, to the most attentive observation, the slight-
est vestige of volatile alkali.
§ 560. 


151 OF THE MILK.
§ 560.
When coagulated, however, by the influence
of spirits of wine, it exhibits the same component
elements of which the milk of those other animals
already mentioned is known to consist. For be-
sides the watery halitus which human milk emits
when recently drawn, and yet in a tepid state, its
serum, separating from the caseous or cheezy por-
tion, contains also the sugar of milk, which is
composed of the saccharine acid united to a calca-
reous earth, together with certain additional parts
oily and mucaginous in their natures. Lastly, it
contains also a cream or butter-like portion, the
globules of which are extremely various and
changeable in their magnitudes, thus vibrating in
their diameters from the tooth to the tooth part
of a line.
§ 561.
The analogy which is observed to exist between
chyle and blood, and between each of these
liquids and milk itself, renders it sufficiently pro-
bable, that this last humour, (which constitutes
at present the more immediate object of our con-
sideration), is a species of chyle renovated from
the volume of blood, or rather separated from this
crimson fluid (with which it had just formed a
junction) previously to its final and complete assi-
milation. This opinion, besides other arguments
K4 which

152 OF THE MILK.
which might be advanced in its favour, derives
powerful testimony from the specific tastes of seve-
ral kinds of aliment being not unfrequently per-
ceptible in the milk of nurses; and also from the
chyle-like habit and constitution of that watery
milk, which not unfrequently exudes from the
breasts of females during the term of pregnancy,
and for a short time after the period of parturition.
§ 562.
The reason why, during the progressive con-
tinuance of lactation, this bland food of the
fœtus becomes gradually more and more inspis-
sated, rich and oily, must be referred chiefly to
the lymphatic veins, with which the mammæ
plentifully abound: Thus the more profuse the
afflux of milk, and the greater length of time this
afflux has continued, with the more power and
uniformity do these lymphatics absorb its serous
parts, and convey them back to the mass of cir-
culating blood, by which means they furnish the
most effective aid to the whole process of this se-
cretion (§ 476).
§ 563.
During the first days after parturition, a very
profuse secretion of milk occurs, and (provided
the mother lactates, i. e. suckles her child) is pro-
moted and kept up by the suction of the infant
itself, 





153 OF THE MILK. 
itself, until the catamenia return, which had for
a long time ceased to flow (§ 547). The exist-
ence of milk in the breasts of virgins truly invio-
late, in the breasts of new-born infants of each
sex, and even in the breasts of men themselves,
as well as in those of other male animals belong-
ing to the class mammalia, is a phenomenon which
not unfrequently presents itself to our observation.
§ 564.
A profuse quantity or accumulation of milk in
the breasts effectually solicits its own final excre-
tion, whence a spontaneous discharge of that fluid
is observed frequently to occur; this discharge
is further promoted by the external pressure of
the mammæ, as well as by the suction of the
tender infant.
SECT. 

154 OF CONCEPTION
SECT. XLIV.
OF CONCEPTION AND PREGNANCY.
§ 565.
HAVING hitherto considered the
structure of the genital organs peculiarly belong-
ing to each sex, we come now to treat of those
functions or processes which constitute the imme-
diate end and destination of these organs, namely,
conception and the propagation of the human race.
In the order and progress of our enquiries into
these abstruse and interesting subjects, we will first
give a plain and simple narrative of the several
phenomena observable in this admirable and truly
divine process; and then attempt an investigation
of the energies from which these phenomena
appear to originate.
§ 566.
It is, in the first place, necessary to observe,
that the subjects of the human race have not, like
most other animals (all those, if I be not deceived,
belonging to the class mammalia, man alone ex-
cepted), any peculiar season of the year in which
they are unusually prone to venereal enjoyments,
but 

155 AND PREGNANCY. 
but are equally liable to experience, at every pe-
riod and under every varying temperature, the
gentle glow of love's diffusive fires.
§ 567.
When therefore, the female of the human spe-
cies admits the embraces of the male, and while
they are thus mutually enwrapt in the ardour of
that animal instinct which far surpasses every other
both in the universality and the potency of its sway,
the uterus (if we be not greatly deceived) being
rendered turgid by a species of inflammatory or-
gasm, and animated at the same time by its own
specific life, (§ 538.) drinks in, as it were, the
seminal fluid emitted by the male, and effects a
synchronous discharge of that which is proper to
itself (§ 543); the fallopian tubes become at the
same time rigid, and with their fimbricated extre-
mities embrace the adjacent ovaria: in one or the
other of these ovaria one of the vesiculæ Graaffianæ
is lacerated or burst, somewhat after the manner
of an abscess advanced to a state of complete ma-
turity, and the albuminoid liquid which this rup-
tured vesicula contained, being absorbed by the
orifice of the embracing tube, is thus conveyed
onward into the cavity of the uterus.
§ 568. 
 

156 OF CONCEPTION
§ 568.
This liquid being discharged from the ovary,
the external lips of the small and recent wound
through which it was emitted, are again united
by a fine cicatrix, while the remaining delicate
vascular membrane in which the liquid had been
enclosed, constitutes what is called corpus luteum.
This body appears to be at first hollow and filled
with a quantity of plastic lymph, that in process
of time is converted into a fleshy nucleus, invested
by a firm cortex or membrane, which is inter-
spersed by a variety of minute, yet remarkable
blood-vessels.
§ 569.
The uterus being thus impregnated, the canal
leading through the cervex or neck of that organ,
especially towards its superior or internal orifice,
(§ 535.) is completely obstructed, in such a man-
ner, that according to the common course of
nature there is no room left for superfœtation.
§ 570.
The internal superfices of the uterus appears to
be invested with a slight inflammatory crust of
plastic or coagulable lymph, (§ 19.) which forms
the membrana caduca, (called also membrana de-
cidua), of Hunter.
This 

157 AND PREGNANCY. 
This membrane-like crust physiologists distin-
guish into two laminæ or layers; one of which,
denominated lamina crassa, invests the whole
internal cavity of the uterus, except the imme-
diate openings into the fallopian tubes, and the
internal orifice of the cervical canal; while the
other is the growth of a later period, and appears
to be generated in the following manner, viz.
after the formation of the ovulum is fairly com-
menced, and this minute body begins to strike its
roots into the decidua, already mentioned, this
second lamina begins gradually to expand, and is
thus continued from the place where those minute
roots begin to pullulate, over the remaining
superficies of the ovum, whence it has been
distinguished by the name of caduca reflexa.
§ 571.
Although the ovulum be formed itself at an
earlier period than the embryo which it is destined
to contain, yet the real organization of the former
seldom commences earlier than the termination of
the first week after conception. For I very much
doubt, whether or not, at an earlier period than
this, any unequivocal vestige of an organised body
has been ever observed in the impregnated uterus
of the human subject.
§ 572. 


158 OF CONCEPTION.
§ 572.
This ovulum, or little egg, is composed of two
proper membranes, besides that external adven-
titious covering, which it derives from the caduca
of Hunter.
The proper membranes are, first, an external
one, apparently destitute of blood-vessels, which
forms the chorion of modern writers. From the
earliest origin of this membrane a great part of its
external superficies is beautifully set with knot-like
flocculi or minute piles of inconceivable elegance,
from whence it has been called, chorion muscosum
seu frondosum, i. e. the moss-like, or leaf-like,
chorion. By means of those delicate piles, which
constitute the rudiments of the fœtal part of the
future placenta, the ovulum is inserted (as if by
roots) into the decidua uterina. (§ 569.)
The other membrane, lying interiorly, is deno-
minated the amnion, which is also destitute of
blood-vessels, (§ 5.) it is indeed delicate and ten-
der, but yet of remarkable tenacity and strength.
§ 573.
For a few weeks after the first formation of the
ovulum, its two proper membranes differ very
widely from each other in point of size, the
chorion exhibiting the appearance of a larger
bladder, 


159 AND PREGNANCY. 
bladder, to the inside of which the amnion
adheres under the form of a smaller one, and is
attached in particular to that part which is
opposite to the centre of the external floccose
superficies of the chorion.
The interstice which then exists between the
chorion and amnion is filled with a very subtle
chrystaline water, of doubtful origin, and transient
continuance.
For when the amnion begins, during the first
months after conception, to increase with greater
rapidity than the chorion, and to gain on the
latter membrane in point of magnitude, this chrys-
taline liquor must necessarily undergo a synchro-
nous, and perfectly correspondent, diminution.
§ 574.
The internal membrane of the ovum, from the
earliest period of its formation (§ 570), till the
final close of parturition itself, is constantly filled
with a fluid, denominated by physiologists, liquor
amnii. This liquid is aqueous, and of a pale
yellowish colour; it emits scarcely any odour, and
is to the taste bland, with a slight saline impreg-
nation hardly perceptible; physiologists generally
suppose it to be a source of nourishment, and
compare it to the white of an egg, from which it
notwithstanding, 

160 OF CONCEPTION
notwithstanding, differs in a very obvious and
essential manner, as may be easily demonstrated by
an attentive experimental investigation.
The sources of this fluid are as yet doubtful: It
is certainly, however, neither derived from the
fœtus nor the umbilical cord, as it is not unfre-
quently found in abortive ovula, which contain
neither of these bodies.
The quantity of this fluid is in an inverse pro-
portion to the bulk of the fœtus. Thus the
smaller and more tender the embryo, the more
profuse is the volume of liquor amnii, and vice
versa.
Hence we are at liberty to hazard a conjecture
respecting the primary use of this liquor, which
appears to be subservient, not so much to the
nutrition, as to the protection and defence of the
minute body of the tender embryo, as yet in a
gelatinous state, and, therefore, wholly unable to
bear the violence of external injuries. With
respect to that small portion of the liquor amnii,
which has been sometimes (though so rarely as to
deserve to be esteemed a preternatural occurrence)
found in the stomach of the fœtus, it cannot
possibly be destined for the purpose of its nutrition,
as will be obvious to any one who considers how
2 extremely 

161 AND PREGNANCY.
extremely inert and empty the chyliferous system
of even a more mature fœtus appears, how unfit
for, and even how averse from, the arduous and
important process of chylification. To the forego-
ing circumstances we might (if necessary) subjoin
various examples of fœtuses destitute of heads,
with diverse other arguments of a similar nature,
and tending to the establishment of a similar result.
§ 575.
The embryo itself, which (suspended by the
umbilical cord, as fruit appended to its foot-stalk),
floats in this liquor, begins to be formed about
the third week after conception: it appears first
under the very simple globe-like figure of a small
bean or kidney, to which the rudiments of the
extremities are gradually subjoined, the symmetry
and specific form farther completed, &c.
§ 576.
According to the usual course of nature, the
female of the human species is uniparous, and con-
ceives only one fœtus at a time. She not unfre-
quently, however, bears twins, the proportion of
which to solitary births is, according to the calcu-
lations of Suffmilch, as one to seven. In a case
of twins each fœtus has its own amnion, but they
are both enveloped in a common chorion.
VOL. II. L That 

162 OF CONCEPTION
§ 577.
That medium, by the aid of which a recipro-
cal intercourse is preserved between the embryo
and mother, are the umbilical cord, and the pla-
centa through which this cord is minutely dis-
tributed.
§ 578.
The umbilical cord, which appears to be co-
eval with the embryo itself, is indeed very strik-
ingly diversified, not only in point of length and
thickness, but also with respect to the place of
its insertion into the placenta, its varicose protu-
berances, &c. In general, however, it is formed
of the spiral contortions of three blood-vessels,
namely, a vein running to the liver of the fœtus,
and two arteries which originate from the inter-
nal iliacs or hypogastrics. These vessels are se-
parated and distinguished from each other by cel-
lular partitions, running in various directions, and
have their lights or diameters frequently straitened
by the small nodes or valve-like bodies of Ho-
boken.
These vessels are collected and compacted to-
gether into a cord by means of cellular membrane,
which being filled with a singular and very limpid
humour, exhibits the appearance of jelly, but is in-
vested externally by a continuation of the amnion.
§ 579.


163 AND PREGNANCY.
§ 579.
At the place where the fœtus is attached to
this cord, the latter is joined by a peculiar body,
which originates from the bottom of the vesica
urinaria (§ 486.), and pursues a middle course
between the two umbilical arteries, namely, the
urachus. This body is, in the human species,
pervious, for at least a short space, and afterwards
totally disappears; but in other animals belong-
ing to the class mammalia, leads onward to what
is called the allantois. Of this allantois the human
fœtus appears to be entirely destitute, unless we
be inclined to designate by this name that myste-
rious and transient vesicula umbilicalis, uniformly.
observable in the human ovula, between the cho-
rion and amnion, which (if I be not greatly de-
ceived) Isbr. de Diemerbrock first discovered long
before it was seen by Albinus or Zinn. But in
more modern times it is discovered too frequently,
and with too uniform an aspect in unvitiated and
fruitful human ovula, (even to so late a period as
the third month after conception), to be any
longer considered as an accidental, a morbid, or
a monstrous conformation of the part.
§ 580.
The blood-vessels of the cord, of which we
have already spoken, pass into the placenta, which
was formerly said to originate from the leaf-like
L2 superficies

164 OF CONCEPTION
superficies of the chorion, a membrane attached
to, and even inserted in, the decidua crassa:
Hence we perceive that the placenta is a body
composed of two different kinds of substance, re-
ceived from an equal number of sources. Thus,
for example, one kind called the uterine, from its
immediate apposition to that organ, is derived
from the decidua, and constitutes the spongy pa-
renchymatous portion of the placenta; while the
other belonging to the fœtus, and therefore call-
ed the fœtal part, is derived from the umbilical
vessels distributed throughout the chorion.
At this time the increase of the tender ovum
is unequal, so that the growth of the smooth por-
tion of the chorion is greater and more rapid
than that of the muscosum or moss-like; hence
it is evident, that the relative magnitude of the
placenta to that of the whole volume of the egg,
is greater in proportion as the conception is more
recent, and less, on the other hand, accordingly
as the period of parturition is nearer.
As pregnancy gradually advances, the placenta
becomes more and more close and compact in its
texture; it is impressed with grooves, and distin-
guished into lobes on its external surface which
respects the uterus, but is smooth and highly po-
lished on its internal, which, looking towards the
fœtus, 

165 AND PREGNANCY. 
fœtus, is invested or lined by the amnios. With
regard to magnitude, thickness, figure, and situa-
tion or point of cohesion to the uterus, it is sub-
ject to a multitude of diversities; it is attached,
however, for the most part, to the fundus or bot-
tom of that organ; and is, upon the whole,
equally destitute of both sensibility (§ 205.) and
genuine irritability (§ 307).
§ 581.
Although all physiologists uniformly concur in
this, that the placenta is the principal organ
through the medium of which the tender fœtus
is supplied with nutriment, yet various contro-
versies have latterly existed among them respect-
ing the genuine mode of its official action, and its
reciprocal relation, as well to the uterus as to the
fœtus. From an attentive and impartial conside-
ration of all the testimony that can be collected
on this subject, the result appears to be, that there
exists no direct anastomosis between the blood-
vessels of the maternal uterus and those of the
umbilical cord; but the arterial blood which passes
by a continuous route from the uterus of the
mother to that portion of the placenta that owes
its origin to the decidua crassa, is there absorbed
by the incipient radicles of the umbilical veins,
that are distributed throughout the moss-like por-
tion of the chorion, and thus conducted into the
L3 venous 

166 OF CONCEPTION
venous trunk of the funis umbilicalis: while, on
the other hand, the blood which is conveyed
back from the fœtus by the umbilical arteries,
being in like manner effused into the parenchyma
of the placenta, is taken up by the venous radi-
cles of its uterine portion, and thus finally re-con-
veyed into the substance of the uterus itself.
The foregoing opinions receive additional con-
firmation from the many well guarded but fruit-
less attempts that have been made by different
physiologists to inject the vessels of the umbilical
cord through those of the uterus, or, on the other
hand, to fill the vessels of the latter organ by in-
jections forced through those of the former. As
a further evidence in support of the same prin-
ciples, we may mention the difference which is
observed to exist between the pulse of the mother
and that of the fœtus before their final disen-
gagement from each other; and lastly, it may
not be improper to add, as a circumstance tend-
ing to the establishment of the same result, the
observations which we formerly delivered respect-
ing the difference between the nature of the
fœtal and that of the maternal blood (§ 147).
But further, it appears probable that a portion
of chyle is also conveyed to the fœtus along with
the blood of the mother. For besides the conside-
ration, 

167 AND PREGNANCY.
ration, that the blood of the mother is not at all
times equally pure and unmixed, but, for some
hours after every meal, carries along with it, in
an unassimilated state, that portion of chyle re-
cently received from the thoracic duct, it has
been demonstrated, on a former occasion, that the
uterus itself possesses a singular and strong affinity
to the chyle and milk (§ 550. 553.); and there
are also on record a great variety of observations,
from which it appears, that a milky juice has been
actually discovered in the uterine portion of the
placenta.
§ 582.
During the progressive advancement of preg-
nancy, while the fœtus and secundines increase so
very remarkably in magnitude, it is obvious that
the uterus must be also subjected to striking and
remarkable changes. Besides the augmentation
of its bulk, so extremely evident at first view,
those changes respect also its situation and figure,
but affect more especially the texture of this sin-
gular and important viscus. Thus, in consequence
of the uniform and weighty congestion of humours
which the gravid uterus is obliged to sustain, it
is likewise subjected to extreme alteration, both
with regard to the state of its blood-vessels, and
L4 also 


168 OF CONCEPTION
also with respect to that of its parenchymatous
portion, throughout which those vessels are inter-
woven.
On the present occasion it may not be impro-
per to observe, that in proportion as the impreg-
nated uterus advances in magnitude, its blood-
vessels lose that mazy and convoluted appearance,
for which they are at other times so very remark-
able, and assume courses much more rectilineal or
direct; while at the same time they are subjected
to a considerable extension of their diameters, and
a consequent increase of their real capacities.
Thus, even the uterine veins have become so ex-
tremely capacious and prominent, as to have been
mistaken by numerous anatomists for true sinuses.
With regard to the parenchymatous portion of
the impregnated uterus, it becomes gradually
more and more lax and spongy, especially where
it is in contact with the ovum contained; so that
towards its sundus or bottom it becomes consider-
ably thick, and in a living and healthy female, is
greatly distended with blood, and possesses the
powers of life in a very high degree. This or-
gan is, notwithstanding, soft at the same time,
and very widely different in its general habit and
appearance from the firm and compact flesh of the
uterus 

169 AND PREGNANCY. 
uterus in an unimpregnated state: this difference
is still more striking if the subject containing the
gravid uterus be dead, in which case, provided
pregnancy be considerably advanced, this organ
falsely assumes in its texture (as was formerly well
observed by Arantius), a lamellated appearance.
It may not be amiss, on the present occasion,
briefly to enumerate a few more of the most
important changes to which the gravid uterus is
subjected, together with the most remarkable ones
that occur in the ovum and fœtus. These changes
we will consider in the successive order in which
they appear throughout the series of ten lunar
months, which period of time is now, with suffi-
cient propriety, supposed to constitute the most
natural term of pregnancy.
§ 583.
As we uniformly observe the uterus beginning
to swell shortly after the time of impregnation,
(§ 567.) so being from that period increased both
in bulk and weight, it descends a little deeper into
the superior part of the vagina; notwithstanding
this descent it still retains its former figure in all,
except the following, respects, viz. its fundus
becomes a little more convex, its anterior paries
or wall, recedes a little farther from the posterior,
and its cavity, which was before very narrow and
almost 

170 OF CONCEPTION
almost triangular, now accommodates itself to the
globose figure of the ovulum it encloses.
About the end of the first month, the ovulum
itself amounts to the size of a pigeon's egg, and
has the two deciduæ separated from each other,
and also the small amnion situated at a distance
from the larger chorion: about the termination of
the third month it attains the size of a goose's
egg, the caduca reflexa becomes approximated to
the crassa, and the amnion approaches nearer to
the chorion. The amnion abounds, at this time,
with a profuse volume of fluid denominated liquor
amnii. In this liquor the embryo, as yet very
tender, and extremely small in proportion to the
quantity of the surrounding fluid (being at this
time scarcely equal in magnitude to a small mouse)
appears to fluctuate in a loose and unsteady
manner, and is even now in a precipitate position.
§ 584.
About the fourth month after conception, the
uterus begins to assume more of an oval or some-
what globe-like appearance; its neck being more
and more softened, gradually shortened, and as it
were, destroyed, or rather latterly distended, it
again protrudes upwards, and begins to ascend
from the smaller into the larger pelvis. At the
same time the fallopian tubes themselves, with the
convex

171 AND PREGNANCY.
convex bottom of the uterus being elevated or
borne upwards, are thus extended and elongated;
these tubes are, however, attached and connected
so closely to the sides of the uterus, that they
cannot recede from them, more than one half of
their own length; hence, when only viewed
superficially, they appear to originate and proceed
from the middle of the uterus, which has given
birth to a very erroneous opinion respecting the
astonishing increase of the fundus uteri.
From this time also the fœtus acquires by
degrees such an increased magnitude, as renders
it more proportionate to the capacity of the ovum,
and begins about the same period to fix itself in a
more steady and firm position, which it preserves
till the very close of parturition: in this position
its head is placed in a downward direction, and
and its face turned towards the lumbar region of
the mother, inclining, for the most part, somewhat
obliquely towards the left side.
§ 585.
In the middle stage of pregnancy, which occurs
about the end of the fifth month, the uterus has
attained such a magnitude, that its fundus is
elevated to a point half-way between the pubes
and umbilicus, and the pregnant state becomes now
observable 

172 OF CONCEPTION
observable from the external appearance of the
abdomen.
About the same time, the fœtus becomes more
perceptible to the mother from the agitative mo-
tion of its body, though we are not able to deter-
mine, with accuracy and definitude the precise
period of time at which this motion takes place.
It appears now, however, to be more vigorous
and active, so that, according to the common use
and acceptation of speech, it may be said to be
the unequivocal action of life.
§ 586.
Throughout the five remaining lunar months
the uterus, with the fœtus which it contains, make
gradually still farther advancements in point of
magnitude. Thus, at the end of the sixth month
they reach nearly to the umbilicus or navel; and
about the termination of the eighth approach
even the scrobiculus cordis, in consequence of
farther protrusion upwards. The cervix uteri is
in the mean time more and more obliterated, re-
duced nearer to a level with the adjacent parts of
that organ, and its parietes or walls considerably
diminish in thickness.
§ 587. 
 

173 AND PREGNANCY. 
§ 587.
Finally, about the end of the tenth month after
conception, the uterus being oppressed and over-
powered as it were, by its own bulk and weight,
(its longitudinal axis, amounting in general to 11,
and its transverse to 9 inches in length) begins
again to subside, and as the period of parturition
approaches, its ostium or mouth is gradually ex-
panded, and thus exhibits an orbicular or ring-like
opening.
Each membrana caduca, more especially the
reflected one, which adheres to the chorion,
having been gradually attenuated for several
months immediately preceding, exhibits now a
kind of net-like appearance distinctly marked by
short fibres of a whitish colour.
Such is the size of the placenta at this advanced
period, that its greatest diameter or breadth
amounts to about 9 inches, its least diameter or
thickness to about one inch; and its weight to
about one pound, and sometimes more.
The length of the umbilical cord for the most
part equals, and sometimes even exceeds, eighteen
inches.
The 


174 OF THE NISUS FORMATIVUS.
The weight of a mature and well grown fœtus
is nearly seven pounds, its length about twenty
inches.
The quantity of the liquor amnii is so extremely
variable, that it cannot possibly be ascertained
with any degree of definitude; in general, how-
ever, it scarcely amounts to a pound, provided the
fœtus be healthy and robust. 
SECT. XLV.
OF THE NISUS FORMATIVUS.
§ 588.
HAVING thus enumerated and de-
scribed, in a plain and simple manner, the most
obvious and unequivocal phenomena of concep-
tions, together with such changes as are discovered
by attentive observation to succeed each other,
during the progressive course of pregnancy, not
only in the human ovum itself, but also in the
fœtus which it embraces, and contains, we now
proceed to an investigation of those physical pow-
ers, by the influence and efficacy of which the
sublime 

175 OF THE NISUS FORMATIVUS.
sublime and truly astonishing process of generation
appears to be most probably accomplished.
§ 589.
There are not wanting certain characters of
high celebrity and distinction who attempt, even
in our own times, to explain the divine process, in
the following brief and summary manner; they
contend that the genuine work of actual generation
has not, at the present time, any real existence at
all; on the contrary, they allege, that the whole
human race possessed, under the form of original
germs, a joint pre-exstence in the genital system of
one or other of our first parents, and that these
germs have ever been, and are yet, subjected to
gradual evolutions, according as the progressive
lapse of time, aided by the co-operation of specific
causes, has contributed to awaken them to the
enjoyment of open and actual life.
Unfortunately, however, for the advocates of
the foregoing hypothesis, an essential difference
of opinion prevails among them on a point of
considerable magnitude and importance; thus,
while some of them are anxiously in quest of those
original germs among the animalculæ that people
the semen of the male; others are searching for
those microscopic animals with no less industry and
zeal in the ovaria of the female.
§ 590.

176 OF THE NISUS FORMATIVUS.
§ 590.
To the latter of these sects in physiology, I must
acknowledge that I myself was formerly an adhe-
rent. I was lead to adopt the opinion of this
learned body not only by the respectable autho-
rity of its numerous advocates, but also by the
want of another more rational and satisfactory.
At present, however, I am obliged to repudiate
this doctrine entirely, to confess my errrors, and
endeavour if possible to correct them; having
been fully convinced, from a more close and mi-
nute attention to the phenomena of generation,
that nature performs this process in a manner quite
different from that contemplated and embraced in
the theory now under consideration.
§ 591.
For I am indeed daily more and more con-
vinced, that all living organized bodies possess,
from their earliest effort at organization to the
closing glass of their existence, a peculiar power
perpetually active, perpetually efficacious, the
immediate destination of which is, first, to mould
the bodies in which it resides into their native and
specific forms by the mysterious process of gene-
ration, to preserve them afterwards from destruc-
tion by the ceaseless function of nutrition, and, in
case of accidental mutilation, to restore their parts
again, as far as consistent with the regular esta-
2 blishments 

177 OF THE NISUS FORMATIVUS. 
blishments of nature, by the process of repro-
duction. That this energy may not be confounded
with the other kinds of vital energy, let it be
distinguished by the name of nisus formativus.
By this name, however, we mean to designate not
so much a cause as a perpetual and uniform effect,
the existence and reality of which are deduced
from actual observations made on the constant and
universal occurrence of certain physical pheno-
mena. It is thus, with views, and on principles
entirely similar, that we make use of the terms
attraction and gravitation, to denote certain ener-
gies or sources of action, the causes of which
are notwithstanding still involved in more than
cimmerian darkness.
§ 592.
To me it appears, indeed, highly probable, that
a stated period of time is requisite for accomplish-
ing the intimate mixture, the union and complete
concoction or maturity of those various inquiline
humours, belonging to each sex, (§ 518. 524.
542. 543.) which are doubtless discharged into
the cavity of the uterus, during every act of fruitful
coition. This term of preparation having at length
elapsed, and the liquors being fully matured and
brought into the most perfect state of union and
reciprocal influence, the nisus formativus is forth-
with excited into action, by means of which the
VOL. II. M spermatic 

178 OF THE NISUS FORMATIVUS.
spermatic mass, hitherto formless and chaotic, is
partly arranged and organized into the elegant
and beautiful envelopes of the nascent ovulum,
and partly moulded into the figure of the living
embryo which this minute bodies encloses. From
this theory we can assign a satisfactory reason,
why the uterus, for the two first weeks after con-
ception, appears to contain a mass of crude and
shapeless humours alone, and does not exhibit,
even to our best glasses (now brought to very
high perfection), the smallest vestige of an or-
ganized embryo, which, notwithstanding bursts
into view almost instantaneously about the end of
the third week, and is, even on its first appear-
ance, of considerable magnitude.
§ 593.
Of the nisus formativus we are presented with
more remote vestiges throughout every department
of natural bodies, not excluding even the most
simple elements of matter, where original germs
cannot possibly be supposed to have the shadow of
an existence. Thus, the clouds themselves assume
their own determinate forms, and even the stream-
ing torrents or veins of the electric fluid preserve
specific figures. There are, again, in the mineral
kingdom, specimens of metallic chrystallization,
which, if indeed the form alone be considered, and
the 

179 OF THE NISUS FORMATIVUS. 
the prerogative of life kept entirely out of view,
bear the most striking resemblance to truly orga-
nized bodies.
In testimony of the truth of this, we need only
mention the curious hypniform crystals into which
refined or depurated copper shoots when first
reduced to a state of fusion, or that exquisitely
beautiful specimen of native peruvian silver which
they call filicinum or fern-like, from the resem-
blance of its figure to that of the plant denomi-
nated fern.
§ 594.
In like manner both the animal and vegetable
kingdoms afford numerous examples of organized
bodies, in which, from their magnitude being suf-
ficient to render them visible, from their beautiful
and unclouded transparency and from the extreme
rapidity of their progressive growth, the whole
process of generation is completely unmasked as it
were, and may be subjected to the examination of
the naked eye. The result of attentive and minute
observations made on this process in such subjects
as these, will be sufficient to evince, on the autho-
rity of the most indubitable testimony that, at least
in these bodies, no germs pre-exist. In illustration
of the above position it will be sufficient to mention
M2 from 

180 OF THE NISUS FORMATIVUS.
from among the different individuals of the vege-
table kingdoms the conferra fontinalis. And from
those of the animal, the hydra viridis.
§ 595.
I should far exceed the limits prescribed to these
institutions were I to attempt a minute and circum-
stantial detail of the various arguments which, in
my view, nature herself furnishes to prove the
potent influence of the nisus formativus in the
process of generation. It may be proper, how-
ever, briefly to state a few of them, the force and
efficacy of which will appear sufficiently evident
on the slightest examination.
§ 596.
The first argument I shall further propose on
this subject is taken from the history of those
curious and interesting subjects of organized nature
denominated hybrids. From a very beautiful and
celebrated experiment it appears, that, if prolific
female hybrids be successively through several
generations impregnated by males of any given
species different from the species of the females,
the new offspring will gradually deviate so widely
from the original form of the mother, and make
such evident and effectual strides towards that of
the father, as to lose at length every vestige of
similitude to the former, and become finally, (by a
species 

181 OF THE NISUS FORMATIVUS. 
species of arbitrary metamorphosis) completely
assimilated to the external figure and appearance
of the latter.
§ 597.
There exists a phenomenon or fact relative too
the history and production of monsters, (the truth
of which is too well ascertained and established
to admit of a doubt), that merits our attention
while on the consideration of the present interest-
ing and intricate subject. It is a circumstance well
known to naturalists, that those animal produc-
tions denominated monsters (most of which are
supposed, by the advocates for the celebrated
doctrine of evolution, to have pre-existed in a
monstrous germiform state from their original crea-
tion)—it is, I say, well known, that such preter-
natural productions, though very frequent among
certain species of animals in a subjugated or do-
mestic state (more especially among swine), are
notwithstanding very rarely found among the ori-
ginal and free-born animals of the very same spe-
cies, that have never been reduced to an humble
state of domestication, but still range the com-
mons and wilds of nature, wholly exempt from
the tyrannic controul of man.
M3 § 598.
 


182 OF THE NISUS FORMATIVUS.
§ 598.
It is necessary further to observe, that not only
monstrosities co-eval with the birth of animals,
but also subsequent adventitious mutilations and
other species of deformity, whether produced on
the animal system by accident or design, become
now and then completely hereditary; and thus,
what was at first the effect of art alone, may be
said to become at length the actual work of nature
herself.
§ 599.
The phenomena of re-production in general are
much more easily and rationally accounted for, by
considering them as the result of a nisus forma-
tivus, than by referring them to the pre-existence
of partial or local germs. This observation is
more fully and clearly illustrated, and its truth
more forcibly exhibited by an application of it to
some particular instances of re-production, as that
of the nails, for example, which after the entire
loss of the first, are well known to be frequently
regenerated on the second phalanx of the fingers.
§ 600.
Again, in certain parts of the body where no
pre-existence of germs can possibly be suspected,
we not unfrequently see organic parts of a pre-
ternatural 

183 OF THE NISUS FORMATIVUS. 
ternatural order produced by the vis medicatrix
naturæ, when roused into action in consequence
of accidental diseases: As an example, and in
illustration of this, we may mention those small
ossifications known by the name of ossicula Wor-
miana, which, in cases of hydrocephalus internus,
are formed by the provident powers of the ani-
mal system, for the purpose of arching over and
thus completely closing the enlarged fontanel.
§ 601.
Finally, on comparing with candour, and weigh-
ing with impartiality, the various arguments on
each side of the question, it very evidently ap-
pears, that besides a power of exciting to motion
and action, which the advocates for the pre-ex-
istence of germs attribute to the male semen, in
order to render their favourite theory more spe-
cious and plausible, they must also bestow on that
fluid plastic or formative powers of the utmost
extent and influence: Whence it is obvious, that
the doctrine for which they so zealously contend,
is of itself wholly inadequate to the explanation
of the numerous and intricate phenomena of ge-
neration, unless it be aided by the powerful con-
currence of a nisus formativus: Whereas, on the
other hand, the system which we have just pro-
posed on the subject is, without the bold pre-
sumption of pre-existent germs, fully sufficient to
explain all the multiplicity of phenomena attend-
M4 ant 

184 OF PARTURITION.
ant on this divine process. Let us then on the
present, as we should on every other point of con-
troversy, adhere to that doctrine which is most
simple in its nature, and most conclusive in its end,
from a thorough conviction, that an unnecessary
multiplication of entities or causes is no less repug-
nant to real and practical utility, than to the tenor
and spirit of found philosophy.
SECT. XLVI.
OF PARTURITION, AND ITS CONSEQUENCES.
§ 602.
THE fœtus being regularly formed and
fashioned by the energies of which we have hi-
therto treated, and advanced through the pro-
gressive stages of its subsequent growth, till it be
brought to a state of fœtal perfection, must, after
arriving at this particular period of maturity, be
finally ushered into the enjoyment of light and en-
tire life, by the painful business of parturition.
§ 603.
This critical and important period arrives, agree-
ably to the usual order of spontaneous nature,
(which is the only object contemplated in physio-
logy), 
 

185 OF PARTURITION. 
logy), about the termination of the tenth lunar
month, i. e. about the 39th or 40th week after
conception.
§ 604.
When a pregnant female finally arrives at this
eventful crisis, she is forcibly impelled to the la-
bour of parturition by an insuperable necessity,
already said (§ 295.) to be less subject to the con-
troul of the will than that which urges to the per-
formance of any other function belonging to the
human body.
§ 605.
With respect to the causes of a revolution so
determinate and sudden, different and even oppo-
site opinions have been entertained by different
physiologists. When we view, and take into at-
tentive consideration, all the attendant circum-
stances, it appears necessary to refer the cause,
which immediately impels to parturition, to an
eternal law of nature, which has hitherto received
no better explanation than has been given to a
great many other physical phenomena, which take
place in like manner at regular and stated periods;
such, for example, as the metamorphosis of infects,
the progressive stages of eruptive fevers, their
crises, &c. &c. Without subjecting themselves to
the just charge of fancifully entering on an absurd
speculation, 

186 OF PARTURITION.
speculation, certain physiologists have compared a
mature ovum, in the uterus of the human subject,
to the healthy fruit of vegetables, which when
completely ripened, fall spontaneously from their
parent plants, in consequence of a self-constriction
of the vessels through which their nourishment
was conveyed. It has been in like manner ob-
served, that as the period of parturition ap-
proaches, the human placenta suffers a slight de-
gree of constriction, and becomes thus prepared,
as it were, for its impending separation from the
surrounding uterus.
With regard to the opinion entertained on this
subject by physiologists in general, namely, that
the amazing expansion to which the impregnated
uterus is subjected, with a multitude of other im-
pressions or impulsive powers of a like nature, act
as the genuine exciting causes of parturition, it
appears to be very clearly and effectually invali-
dated by a great variety of arguments, which may
be fairly deduced from the unequivocal pheno-
mena of the animal economy itself: of these argu-
ments we think proper to mention the following,
namely, in numberless genuine cases of extra-
uterine conception, where the fœtuses have been
contained, for example, in the Fallopian tubes, or
in the ovaria, the uterus has notwithstanding been
attached by painful and convulsive throws, about
the 

187 OF PARTURITION. 
the termination of the tenth lunar month after the
occurrence of such preternatural conception.
§ 606.
Besides the exciting, it is evident that there
must be also the joint co-operation of very pow-
erful efficient causes, arising from the nature and
properties of the uterus itself, and of the contents
which it encloses.
The proximate or immediate and primary cause
must be doubtless referred solely to the vita pro-
pria, or specific life of the uterus itself (§ 47.)
Of the remote causes the leading and most con-
siderable appear to be, the powerful efforts which
are made by the assistance of the process of respi-
ration, and the extensive consent or co-operation
of the intercostal nerve with the other portions
of the nervous system.
§ 607.
When finally the labour of genuine parturition
is excited, its phenomena observe a determinate
and regular order with regard to their commence-
ment and subsequent progressive course. In con-
sequence of this, they have been divided by ac-
coucheurs into different stages, of which four
have been enumerated by the latest writers on the
obstetric art.
§ 608. 


188 OF PARTURITION.
§ 608.
In the first stage, the parturient patient expe-
riences a slight attack of those peculiar and well-
known pains, called in that state precursors oi
warnings, which shoot in a direction from the 
loins to the lower parts of the uterus, and which
are indeed felt at intervals, (though with dimi-
nished frequency and force), throughout the whole
period of parturition: the orifice of the uterus
begins, at the same time, to be considerably di-
lated, the abdominal tumor subsides, an inclina-
tion to pass urine becomes urgent and trouble-
some, and a copious discharge of mucus takes
place from the genital organs, now in a state of
distension and laxity.
§ 609.
In the second stage, the pains increase, and are
now distinguished by the name of preparantes, or
preparatory efforts: the inferior segment of the
coverings or membranes of the ovum are, at the
same time, protruded through the uterine orifice
into the vagina.
§ 610.
In the third stage the pains still continue greatly
augmented in their violence, and are now denomi-
nated dolores ad partum *. They act against the
* i. e. The genuine pains of parturition.
uterus

189 OF PARTURITION. 
uterus with a more violent impetus, and thus
potently protrude it downwards, while, at the same
time the uterus presses with such astonishing force
on the encarcerated fœtus, as to occasion a rup-
ture in the membranes by which it is inclosed.
§ 611.
During the fourth and last stage of parturition,
while the patient is agitated with convulsive throws,
and tortured with the most excruciating pain, she
makes, at length, a violent exertion, (not un-
frequently accompanied with horripilation, grind-
ing of the teeth, trembling of the knees, &c.), by
the impulsive force of which, the head of the
emerging infant is urged forward, and finally pro-
truded quite through the external orifice with its
face foremost: in this unlooked for position it is
forced to advance, in consequence of the vertex
or crown of the head becoming lodged against the
arch of the pubes, while its other parts are urged
onward, and obliged to revolve on the stationary
vertex, as on an axis, or centre of motion. Thus,
amidst a profuse discharge of blood, the infant is
finally excluded from its place of confinement, and
introduced to the enjoyment of light and life.
§ 612.
The fœtus being thus happily excluded, the
birth of the secundines succeeds, after a short in-
terval, 

190 OF PARTURITION.
terval, accompanied, in like manner, with painful,
though much less violent, throws: this latter birth
is, as well as the former, followed by a discharge
of blood, from that part of the uterine cavity to
which the placenta adheres by means of the
crassa or gross membrana decidua.
§ 613.
The uterus, being thus, at once delivered of
its two-fold birth, by which it had been encum-
bered and oppressed, is now contracted by little
and little, till it is finally restored to its former
figure, and reduced almost to its former size.
§ 614.
During the first week after the birth of the
child, there exists, from the genital organs of the
mother, an uninterrupted effusion of the lochia,
a discharge very much resembling the catamenia,
except that it is more profuse in quantity, espe-
cially when not in any measure checked or dimi-
nished, by the commencement of lactation. The
bloody or florid colour of the liquid discharged by
this evacuation is, notwithstanding, changed about
the fourth day to a pale red, and from thence
passes on to assume a white appearance.
As soon as the uterus is thoroughly cleansed
of all remaining fragments of its deciduous mem-
brane, 

191 OF THE HUMAN SUBJECT, &c. 
brane, and has thus finally completed the painful
and tedious task of propagation, it may again
resume the natural process of menstruation, or
even return to the performance of fresh immola-
tions on the altar of conception itself.
SECT. XLVIII.
OF THE DIFFERENCES BY WHICH THE HUMAN
SUBJECT IS CHARACTERISED BEFORE AND AFTER
BIRTH.
§ 615.
FROM what has been already said
respecting the mode of life enjoyed by the fœtus,
while yet encarcerated within the parietes, and
immersed in the warm-bath of the maternal uterus,
it is extremely obvious that an immense difference
must exist, between the functions of the animal
economy in this state, and that which shortly suc-
ceeds, when the infant is finally introduced, by
birth, into entire life, and is possessed of a power
of spontaneous motion. An enumeration and
statement of the leading points or circumstances
of this difference, constitutes the design of the
present section.
§ 616. 


192 OF THE HUMAN SUBJECT
§ 616.
To begin then with the circulation of the blood,
it must be observed, that the route of this crimson
fluid is different in the fœtal state, from what it is
in that which immediately succeeds paturition or
birth. During the continuance of the former
state, the fœtus is connected, and preserves a cir-
cular intercourse with the uterine placenta, by
means of the umbilical cord; it has never, as yet,
inspired air for the purpose of supplying the blood
with that vital pabulum, a process which immedi-
ately commences and is uniformly continued after
birth, when this reciprocal connection between
the mother and child, is finally destroyed.
§ 617.
The umbilical vein originating from the placenta
of the mother, and passing through what is called
the umbilical ring of the fœtus, directs its course
towards the liver, where it discharges its blood
into the sinus of the vena portarum; from thence
the blood is distributed in part, by the ramifica-
tions of this memorable vein, throughout the liver,
and in part, conveyed by a direct route through
the ductus venosus Arantii, to the inferior or
ascending vena cava.
The two foregoing canals, namely, both that
portion of the umbilical cord which is contained
2 in 

193 BEFORE AND AFTER BIRTH. 
in the abdomen of the fœtus, and also the ductus
venosus mentioned above, suffer after birth an
entire obliteration of their cavities, and assume the
nature and appearance of solid cords, insomuch
that the former constitutes what is denominated
the round ligament of the liver.
§ 618.
When, in the fœtus, the blood is conveyed
from the inferior vena cava to the right side of the
heart, the greater part of it is denied a passage
from thence through the lungs, and is therefore
directed towards the left or posterior auricle of
the heart, by the valve of Eustachius, and admit-
ted into that cavity through the foramen ovale.
§ 619.
For over the mouth of the inferior vena cava,
after its ascent from the cavity of the abdomen in
the fœtal state, a valve of a lunated figure is extended,
which, in honour of its immortal discoverer, has
been called the valve of Eustachius. This luni-
form body is, for the most part, gradually oblite-
rated as life advances, although in the fœtal state it
appears to perform the important office of directing
the blood, emerging from the abdominal cavity,
towards an orifice to be spoken of presently, which
penetrates the septum situated between the two
auricles of the heart.
VOL. II. N § 620. 

194 OF THE HUMAN SUBJECT
§ 620.
The orifice referred to in the preceding para-
graph is called the foramen ovale, through which
by far the greater part of the ascending column of
blood, derived immediately from the inferior vena
cava, is conducted into the left auris of the heart
during each diastole of the auricles: of this blood
the regurgitation is effectually prevented, by the
elegant falciform valve formerly mentioned, which
is closely spread over the foramen, and appears to
close that orifice completely, during each systolic
motion of the auricles. During the first years of
infancy the foramen ovale is in part closed by means
of this small valve, and partly obliterated by the
gradual but slow adhesion of its sides: in cor-
respondence to such adhesion, the valve of Eusta-
chius itself undergoes also a slow and gradual
diminution in point of size, till scarcely a wreck of
it is left behind.
§ 621.
Of that blood which, at the same time, enters
the right auricle of the heart from the superior
vena cava, a very small portion only can be received
by the lungs of the fœtus, as yet in a weak and in-
active condition: it is therefore taken up by the
ductus arteriosus, from the trunk of the pulmonary
artery (of which this duct is indeed the leading
branch) and conveyed by a direct and speedy route
to 

195 BEFORE AND AFTER BIRTH. 
to the arch of the aorta, without passing through
the lungs at all. Within the course of a few weeks
after the birth of the infant, the cavity of the
ductus arteriosus is, for the most part obliterated,
and its parietes or walls converted into the nature
and appearance of a dense and firm ligament.
§ 622.
The blood being propelled through the trunk
of the aorta, that portion of it, destined to be
re-conveyed to the system of the mother, enters
the umbilical arteries (§ 578.) which pass through
the annulus umbilicalis, on each side of the urachus,
and are, in like manner, after the birth of the
infant, converted into solid imperforated cords.
§ 623.
As the lungs perform in the fœtus scarcely any
function at all, their general habit and appearance
differ very materially from those which they assume
after the infant has commenced the process of
respiration. Thus, their bulk is proportionably
much less, their colour more dark, their substance
more compact, and hence their specific gravity so
much greater, that when immersed, recent and
free from putrefaction, into a vessel of water, they
fink instantly to the bottom; whereas, on the
other hand, if the infant has been born in a living
state, and taken in air by inspiration, these viscera,
N2 the 


196 OF THE HUMAN SUBJECT
for the most part, float on the surface of water, or
of any other fluid equally ponderous. The right
lobe of the lungs appears to possess the peculiar
prerogative of being dilated a little sooner than
the, left by the incipient influx of air in the first act
of inspiration. With regard to the other pheno-
mena of this new function of life, they were
enumerated formerly, when we were treating
particularly of the process of respiration.
§ 624.
From the observations which were formerly
proposed on the nutrition of the fœtus (§ 574,
581.), it may be very easily perceived that the
state and condition of the alimentary tube and chy-
lopoietic system, are extremely different before,
from what they are after, the birth of the infant,
these viscera being in the first case inert and
wholly incapable of action. Thus, for instance,
in the tender embryo of only a very few months
existence, the larger, are perfectly similar in habit
and appearance to the smaller, intestines; but
during the closing months of pregnancy the former
portion of the intestinal canal (being considerably
distended with meconium) appears to merit unequi-
vocally that name by which it is afterwards dis-
tinguished from the latter.
§ 625. 

197 BEFORE AND AFTER BIRTH. 
§ 625.
The meconium is a peculiar species of saburra,
of a green colour, shaded with more or less of a
brownish cast. It is doubtless derived from the
inquiline humours of the fœtus itself, more espe-
cially from the bile: that it is indeed of a bilious
origin we are induced to believe from the follow-
ing considerations:—First, because the earliest
appearance of this excrementious substance corres-
ponds exactly, in point of time, with the com-
mencement of the biliary secretion; and, Secondly,
because we learn from accurate observation, that
such monsters as are destitute of a liver, have their
intestines supplied with nothing else but a small
quantity of colourless mucus instead of the more
common and natural meconium.
§ 626.
In the new-born infant the form of the cœcum
is also very widely different from what it is in the
future periods of life; and this intestine is then
continued in a direct line with the appendicula
vermiformis.
§ 627.
Several other differences and peculiarities, of a
similar nature, we have already spoken of on parti-
cular occasions, and shall here, therefore, only
N3 glance 
 

198 OF THE HUMAN SUBJECT
glance on them in the most brief and transient
manner:
They are the Urachus (§ 579.) the membrana
pupillaris (§ 259.) and, in the male fœtus, the
descent of the testes (§ 501.)
A few additional peculiarities will be spoken of
with more propriety in the following section.
Others, as being of less importance, we volun-
tarily pretermit in perfect silence.
§ 628.
The present appears to be indeed a very fit
and favourable opportunity for calling the attention
of the reader to three parts of the human body,
altogether peculiar in their nature and obscure in
their destination, which are of a greater propor-
tional size in the fœtus than in the adult, and
appear to be in a special manner subservient to
the economy of the former. The true and une-
quivocal uses of the parts now in contemplation
have not as yet, however, been clearly and satis-
factorily ascertained, although, anxiously sought
after by the combined labours of numerous and
very respectable anatomists. These parts are
designated by the name of glands, although their
parenchyma is far, very far, different from the
glandular, and they have never been discovered
to 

199 BEFORE AND AFTER BIRTH. 
to possess the faintest vestige of an excretory duct.
They are denominated the thyroid gland, the
thymus, and the renes succenturiatati.
§ 629.
The thyroid gland is situated on the anterior
side of a cartilage of the same name, which enters
into the conformation of the larynx. It consists
of two lobes, and is of a lunated or falciform
figure; in the fœtus it is distended with a lympha-
tic fluid, but, as life advances, becomes gradually
more and more spoliated of its distending liquid.
§ 630.
The thymus consists of a mass of shining and
very tender flesh, is, in like manner with the pre-
ceding substance, bilobular, now and then divided
into two distinct portions, and contains also occa-
sionally a cavity of considerable dimensions. This
body is situated beneath the middle and upper
part of the sternum, and ascends on each side even
to the throat itself; in the fœtus it is large,
irregular in its figure, and abounds with a juice of
a milk-like nature; but as youth advances it gra-
dually diminishes in size, until, finally, on the
accession of old age, it is so completely obliterated
as to exhibit scarcely a shadow of its former
existence.
N4 § 631. 


200 OF THE INCREASE, MATURITY,
§ 631.
Lastly, The Renes succenturiatali, (called like-
wise glandulæ suprarenales, capsulæ atrabiliariæ.
&c.) are situated beneath the diaphragm, resting
on the upper extremities of the kidneys. In adults
they are not only diminished in size, but are also
removed to a small distance from the contact of
the kidneys, and contain a dark coloured fluid,
which in the fœtus is more inclined to a pale red.
SECT. XLVIII.
OF THE INCREASE, MATURITY, AND DECLINE
OF MAN.
§ 632.
HAVING hitherto minutely considered
the human economy, in detail, agreeably to the
several classes into which its physical functions are
divided, nothing further remains at present than
to take a general, brief, and comprehensive survey
of man in his transit over the diversified stage of
life, and thus accompany him, from his earliest
vital pulse in an embriotic state, throughout the
leading, 


201 AND DECLINE, OF MAN. 
leading revolutions and æras in his economy, down
to the final termination of his existence.
§ 633.
First, then, about the third week after concep-
tion, the rudimental organization of the embryo
appears to take place (§ 575.): about the fourth
week afterwards, while the embryo still enjoys an
extremely low and languid degree of life, border-
ing even on that of a vegetable, it is supplied with
the first portion of genuine red blood (§ 13.)
The motion of the corculum or minute heart, has
been but very seldom observed by physiologists in
the incipient human embryo, but was long since
discovered by Aristotle in the incubated chick, and
has been, from that period, designated by the
name of the punctum saliens.
§ 634.
About the seventh or eighth week after con-
ception, the momentous process of osteogeny, or
the generation of bone, commences in the human
subject. Those parts where osseous, or bony
matter makes the first depositions for the formation
of its nuclei, are the clavicles, the ribs, the verte-
bræ, the long cylindrical bones of the extremities,
the mandible or lower jaw, and certain other
bones of the face, &c. Those parts again where
the osseous depositions are secondary in point of
time, 

202 OF THE INCREASE, MATURITY,
time, are some of the plain bones of the skull,
such, for example, as the frontal and occipital:—
while the bones of the neck, &c. are formed at a
still later period.
The younger the embryo is, in particular, or to
proceed on a more extensive and general scale,
the younger the human subject is, whether before
or after birth, with the greater rapidity does its
growth advance, and vice versa.
§ 635. 
About the middle period of pregnancy, the
fœtus becomes what may be called a genuine sub-
ject of vitality or life, agreeably to the rule of
discrimination laid down on that particular point in
a former part of this work (§ 585.) About the
same time, the secretion of certain humours make
their first appearance, such, for example, as the
fat (§ 38) and the bile.
§ 636.
As the fœtus advances towards maturity the
tender hair begins to pullulate, the nails emerge
into view, the membrana pupillaris gives way
(§ 260), and in the male sex the testes begin to
descend (§ 505).
§ 637. 

203 AND DECLINE, OF MAN.
§ 637.
About the close of the tenth lunar month, the
infant is finally released from its imprisonment by
means of parturition (§ 603); after which, besides
the astonishing revolutions in almost the whole
economy of its system, detailed more amply and
minutely above, it is also subjected to various
changes in its external habit and appearance;
thus, for instance, that delicate lanuginous hair,
with which the face of the new-born infant is
overspread, disappears by degrees, its wrinkles are
gradually obliterated, its anus retires within the
nates, which now begin to be slowly protruded,
&c. &c. &c.
§ 638.
The infant also learns, (though indeed by very
slow degrees), the exercise of the various faculties
of the mind, such, for example, as those of per-
ception, of attention, of reminiscence, of desiring,
&c. &c. from whence, in a very few months after
birth, it is subjected to dreams, &c.
§ 639.
The organs of the external senses undergo also
gradual or progressive improvements, and are
advanced to still higher and higher degrees of
perfection, such as the external ears, the internal
nares,

204 OF THE INCREASE, MATURITY,
nares, also the coverings of the eyes, such as
their supra-orbital arches, their supercilia, &c.
§ 640.
The bones of the cranium acquire, in the mean
time, an augmented degree of firmness. The
fonticuli or chasms between the different bones
are gradually arched over, and about the eighth
month the process of dentition commences.
§ 641.
The infant is now ready to undergo ablactation
or weaning, being furnished with teeth for the
express purpose of subduing more solid food, and
not to injure the papilla, or nipple of the mother.
§ 642.
About the close of the first year, the infant
learns to stand alone, and support itself in an erect
position, the greatest and most enviable prerogative
with which the human body is dignified.
§ 643.
The infant being thus removed from its mother's
breast, and possessing the use and command of its
feet, makes daily advances in growth, and im-
proves in the power of spontaneous motion, while
it acquires, at the same time, another very import-
ant privilege conferred on the human race, namely,
the use of speech. Ideas which have become
familiar 

205 AND DECLINE OF MAN. 
familiar to its mind it now begins to make attempts
to express by the aid of that important organ the
tongue.
§ 644.
About the seventh year of life, the milk-teeth,
or first set, being twenty in number, drop out by
degrees, and are replaced in a series of years by
a second dentition, consisting of thirty-two peren-
nial or permanent teeth.
§ 645.
During this period of infancy the memory far
surpasses in strength and perfection the other pow-
ers of the mind, and appears to be indeed in a
very peculiar manner adapted for receiving and
retaining the signs of things; whereas after the
fifteenth year of life, the glowing powers of the
imagination usually gain the ascendency.
§ 646.
This superior strength and activity of the ima-
gination very happily manifests itself throughout
those years of life in which the human subject is,
by a variety of striking and very important
changes in the body, gradually prepared for the
future performance of such functions as constitute
the characteristic distinctions between the two
sexes.
§ 647. 

206 OF THE INCREASE, MATURITY,
§ 647.
Shortly after this period the mammæ or breasts
of the female subject begin to swell, the chin of
the male becomes clothed in a mantle of coarser
down, and a variety of other phenomenon occur
in each sex, which serve in like manner to an-
nounce the gradual approach of puberty: thus,
in the female the catamenia begin to flow; while
in the male the secretion of a true semen com-
mences, which is uniformly accompanied by a
more luxuriant crop of beard, and a very striking
change in the voice from a shriller to a graver
tone.
About the same time the sexual instinct (§ 289.)
that spontaneous and potent call of nature, is first
awakened into action, and man, now in the blos-
som of life, is fitted and inclined to venereal en-
joyments.
§ 648.
The crisis or precise period of puberty cannot
by any means be accurately ascertained. It is
much varied by diversities of climate and of tem-
perament. In general, however, it occurs earlier
in the female than in the male sex; thus, in our
climate females may be said to have arrived at
this interesting period against the fifteenth, but
males not before the twentieth year of life.
§ 649. 

207 AND DECLINE OF MAN. 
§ 649.
Shortly after the above period the human body
finally ceases to increase stature; this particular
is also influenced and greatly diversified by differ-
ence of climate, not to mention the countless va-
rieties that are exhibited relative to this point,
not only by different individuals, but even by
whole families.
§ 650.
About this period also the epiphyses, which had
been hitherto distinguished from the bones to
which they were attached by very visible lines of
separation, become so intimately united to, and so
completely coalesce with these bones, that not a
vestige is left to serve as a memento of their for-
mer distinction.
§ 651.
With respect to the term of perfect manhood,
which constitutes indeed the most lengthy, as well
as most useful and important period of human
life, we find it characterised by the highest de-
grees of vigour and uniformity, when we examine
the functions of the body, and by that most inva-
luable prerogative, maturity of judgment, when
we take into consideration the faculties of the
mind. Throughout this interesting period the
lamp 

208 OF THE INCREASE, MATURITY,
lamp of human life blazes with the highest degree
of intensity and splendor.
§ 652.
The heralds which unerringly announce the in-
trusive approach of old age are, in females, the
cessation of the catamenia, (§ 547.), in males, a
languid propensity to venereal gratifications, and
in both an invasion of what is called the rigidity
or dryness of old age, with a flow but sensible de-
clination of the vis vitæ, or aggregate power of
performing the various functions of life.
§ 653.
Finally, the frigid reign of the ultimate degree
of old age is strongly characterised by the follow-
ing concomitant phenomena, namely, a sluggish-
ness and increasing dulness of the senses, both ex-
ternal and internal, an irresistible call for longer
indulgence in sleep, and a torpidity and languor
in all the functions of the animal economy. The
hairs assume a silvery gray, and fall in part from
their exalted situation. The teeth themselves
drop spontaneously from their declining sockets.
The neck is no longer able to support the head,
nor the tottering legs to sustain the weight of the
incumbent body. Even the bones themselves,
those indispensible fulcra of the whole machine,
1 are

209 AND DECLINE OF MAN. 
are obliged to bear a part in this irremediable
and universal decay.
§ 654.
We have thus arrived at length to the remote
ultimatum of physiology, namely, death without
disease, or the euthanasia of old age. To conduct
and protract human life to this only natural ter-
mination (the causes of which are sufficiently ob-
vious from what has been already laid down) con-
stitutes indeed the alpha and omega, i. e. the sole
and exclusive end and object of the healing art.
§ 655.
The phenomena of this natural death (as observed
in man when about to resign himself to its potent
grasp), are, a coldness of the extremities, a loss
of the brilliancy of the eyes, a very small and
slow pulse, accompanied with intermissions pro-
gressively increasing in frequency, and lastly a flow
respiration, which by a more forcible act of ex-
spiration, is at length closed for ever.
In the live-dissections of animals belonging to
the class mammalia, there is a convenient oppor-
tunity for observing the last exertions of the heart,
from which it appears, that the right ventricle
and auricle of that viscus resist the encroachments
VOL. II. O of 

210 OF THE INCREASE, MATURITY,
of death longer, and continue the motions of life
to a later period, than the left.
§ 656.
Coldness accompanied by rigidity, a cadaverous
stench, but more especially a flaccidity of the cor-
nea, and a hiatus or gaping of the anus ascertain
in the most unequivocal manner the complete death
of the body. When in the corpse an aggregate
collection of all these signs occur at once, not even
the sceptical Pliny himself could find room to inter-
pose the shadow of a doubt respecting the complete
extinction of animal life.
§ 657.
To ascertain with definitude the natural term of
the life of man, (or to point out that period
which may be considered as the more frequent and
regular goal or ne plus ultra of human existence),
is, indeed, a matter attended with the utmost diffi-
culty. I have notwithstanding learnt, from exa-
mining with care and comparing with accuracy, a
great number of bills of mortality, that a consider-
able proportion of such Europeans as are advanced
in years reach, but that very few of them pass,
the eightieth and fourth year of life.
§ 658. 

211 AND DECLINE OF MAN.
§ 658.
We may observe upon the whole, that in con-
sequence of the weakness and tender susceptibility
of infancy and childhood, the intemperance and
irregularity of an infinitude of adults, the incon-
trolable violence of diseases, and a countless
multitude of fatal casualties, not more of mankind
than seventy eight in a thousand resign their lives
to that species of death now under consideration,
namely, death without disease. Notwithstanding
the truth and authenticity of the preceding obser-
vation, yet on making a genuine estimate of human
longevity and comparing it, under similar circum-
stances, with that of the other subjects belonging
to the class mammalia, whose natural term of
existence is known to us, it will evidently appear,
that, except the baseless declamations of sophists
regarding the miseries of human life, nothing can
be more unfounded and irrational than their splen-
did and verbose effusions respecting its brevity
O2 
 



APPENDIX,
IN WHICH IS EXHIBITED A
Condensed and Summary View
OF THE
EXISTING DISCOVERIES AND SPECULATIONS
Relative to the Subject of, what is usually denominated,
ANIMAL ELECTRICITY.
STEADY and uniform as the lapse of
time itself, are the exertions made by the enter-
prize and industry of man, to shed light on the
arcana or secret processes of nature. In proportion
as such laudable attempts are prosecuted with
boldness and crowned with success, revolutions and
improvements take place in the various branches
of physical science. Revolutions derive birth from
the detection of error, while improvements result
from the discovery of truth. On the repudiation
of false principles in science, as well as on the
developement of new ones deduced from the reci-
O3 procal 


214 APPENDIX.
procal concurrence of numerous and unequivocal
facts, it is not without the sanction of reason and
propriety that new systems are forthwith compiled,
digested and ushered into the world.
For, to be complete and satisfactory, a system
in any branch of science, should embrace and ar-
range in order all the well authenticated principles
spontaneously resulting from facts already ascer-
tained and observations already made, relative to
that particular branch. A system less general and
comprehensive in its scope than this, should be
deemed, at best, but defective and partial, and
received as the abortive production of a mind
deficient in point of information.
Of the former description was the famous phy-
siological system of Baron Haller, at the time its
illustrious author first submitted it to the eye of the
world. That excellent physician and philosopher
grasped in his acute and comprehensive mind, and
detailed at large, in the work to which I here
allude, all the authentic and well defined princi-
ples resulting from the infinitude of facts with
which the science of physiology was at that time
enriched.
But all systems are stationary and have been as
yet imperfect, while, happily for the interest of
man, 
 

215 APPENDIX. 
man, improvements in science are progressive and
advancing towards perfection. In the course of a
few years, such a blaze of physical light was dis-
fused abroad by the industry and ingenuity of
philosophers in general, but of physicians and
chemists in particular, that the deficiencies and
errors of the Baron's elaborate system were ren-
dered obvious to the most weak and inattentive
observer. In the important doctrines respecting
the causes of animal heat and the nature and
purposes of respiration, in particular, entire revolu-
tions were effected by the numerous and ingenious
discoveries of chemists in that branch of science
denominated aerology.
To supply, as far as possible, the deficiencies
of this system of Haller, and to circumvent the
errors which the authority of so celebrated a cha-
racter might tend to diffuse throughout the minds
of his numerous readers, became desiderata of no
small moment in the science of physiology.
The most effectual method of accomplishing these
desirable ends was too obvious to escape discovery.
For as violence is most effectually repelled by
counter violence, and one disease not unfrequently
removed from the animal system by the impetuous
invasion of another, so in like manner, in science,
the defects of one system are most advantageously
O4 supplied 

216 APPENDIX
supplied, and its errors most effectually contro-
verted and exposed, by the plenitude and unequi-
vocal certainty of the principles of a rival system.
This truth did not escape the observation of that
learned and acute professor, of Goettingen, who
now fills the chair which was formerly rendered
vocal by the eloquence of the immortal Haller.
Need I add, that professor Blumenbach is the man
to whom I allude—a man, for the completion of
whose greatness and utility in physical science,
nature and art appear to have all but exhausted
their abundant resources! For industry and perse-
verance in the collection of materials, for powers
to combine and arrange materials when thus col-
lected, and for ingenuity and acumen to deduce
and speculate from such combination and arrange-
ment, the present age certainly boasts few—too
few physiologists who may be set in competition
with the illustrious Blumenbach.
For this physician and philosopher was reserved
the honourable and important task of collecting,
digesting and consigning to publicity, a system of
physiology destined to supply the deficiencies and
correct the errors of that which had already
resulted from the labours of his celebrated friend
and predecessor. The system of professor Blumen-
bach was, like that of Baron Haller, perfect and
complete 

217 APPENDIX. 
complete at the time in which it was handed to
the world. There existed not, at that period, an
established principle, nor scarcely even a probable
conjecture in physiology, with which he was not
minutely acquainted, and which he did not draw
into the extensive and powerful vortex of his
system.
Had the science of physiology been finally com-
plete at the time in which professor Blumenbach
wrote, the industry, the immense resources and
the comprehensive talents of that philosopher
would, no doubt, have quite precluded the neces-
sity of future systems in this branch of science.
But in the unfathomed depths of the animal
economy more arcana yet existed—more terra
incognita lay yet unexplored, and further re-
searches of enterprise were therefore essential.
By the combined labours of experimental physi-
ologists in different parts of the world, this branch
of science was at length matured for giving birth
to another discovery, which will probably be found
of equal importance, in explaining the phenomena,
and in removing the diseases of the animal system,
with that which consigned to immortality the name
of the illustrious Harvey. The discovery to which
I wish at present to direct the attention of the
reader is that of, what is usually called animal
electricity, 

218 APPENDIX.
electricity, or, of the existence and operation of a
fluid extremely similar to electricity in the living
animal system. For the fortunate Galvani pro-
fessor of anatomy at Bologna, was reserved the
honour of lighting by accident on this beautiful
and divine discovery—a discovery which entitles
its author to be ranked with the great promoters
science and the essential benefactors of man.
That such a fluid did actually exist in the bo-
dies of animals, had been long suspected by phy-
siologists and other speculative philosophers. The
matter rested however on pure conjecture alone,
and was yet unsanctioned by the tests of experi-
ment and observation. The apparent intricacy
of the subject depressed the hopes of the boldest
experimenters, and the subtlety of the investiga-
tion seemed to throw an insurmountable bar in the
road to success. But accident not unfrequently
does more for the real advancement of science,
than boasted genius and industry are able to ac-
complish. It was accident that first suggested to
the celebrated Gallileo the construction and use
of that optical instrument denominated the tele-
scope—It was accident which first led the immortal
Newton to the original conception of that prin-
ciple of gravitation, by which he afterwards ex-
plained, with such facility, the movements and ex-
quisite balance, of the material universe. And it
was, 

219 APPENDIX.
was, in like manner, accident—fortunate accident,
that first suggested to the industrious and acute
Galvani the mode of experimenting, with effect,
on the intricate subject of animal electricity—a
subject which may possibly be destined as the only
proper clue to conduct future physiologists to the
genuine springs and principles of life itself.
" Whilst the professor (alluding to Galvani)
was engaged in dissecting a frog in a room where
some of his friends were amusing themselves with
an electrical machine, one of them drew a spark
from the conductor, at the same time that the
professor touched one of the nerves of the animal.
In an instant the whole body of the frog was
shook by a violent convulsion. The professor
was astonished at the phenomenon, and believed
it owing to his having wounded the nerve; to
assure himself whether this was really the case,
he pricked it with the point of his knife, without
any motion of the body being produced; he now
touched the nerve with the instrument as at first,
and ordered a spark to be taken from the machine,
on which the contractions were renewed. The
experiment was repeated a third time, but the
animal remained motionless; however, upon per-
ceiving he held his scalpel by the handle, which
was of ivory (a bad conductor), he changed it 
for

220 APPENDIX.
for a metallic one, and re-excited the movements,
which he constantly failed of doing whilst using
an electric substance.
" After having made a number of experiments
with the electrical machine, he resolved to prose-
cute the subject with atmospheric electricity. To
this end he raised a conductor upon the roof of
his house, from which he brought an iron wire
into his room, and to this attached metal con-
ductors, connected with the nerves of the animals
destined to be the subjects of his experiments,
and to their legs he tied wires, which reached the
floor. Considerable movements were observed in
the animals, whether of cold or warm blood,
whenever it lightened. These preceded thun-
der, and corresponded with its intensity and re-
petition, and even when it did not lighten the
movements took place when any stormy cloud
passed over the apparatus."
" Professor Galvani one day suspended some
frogs, perhaps with similar views, on metal hooks,
fixed in the spine of the back, upon the iron rail-
ing of his garden; several times he remarked that
these animals contracted, and appeared to receive
shocks; at first he conceived the movements were
owing to changes in the atmosphere, but a more
scrupulous 

221 APPENDIX.
scrupulous examination undeceived him. Having
placed a prepared frog * upon an iron plate in his
room, and happening with his dissecting forceps to
press it against the plate, he observed the move-
ments to take place. This experiment succeeded
with all metallic bodies, but more particularly well
with silver; non-conducting substances were not
proper for it. From this period our author began
to suspect the animal possessed an electricity of its
own; and in this suspicion he was further con-
firmed by the following circumstance:—He held
* That the reader may not be entirely ignorant of what is
meant by a prepared frog, I take the liberty of presenting
him with the following brief extract from the first experi-
ment detailed in Dr. Valli's publication: " My first experi-
ment was made on a frog, in the following manner: I opened
the abdomen in order to lay bare the spine of the back, and
discover the crural nerves which issue from it; a few lines
above this point I cut the animal in two, and by passing my
sciffars immediately under the origin of these nerves, re-
moved the remaining portion of the vertebral column, so
as only to leave the vertebræ which united the bundle of
nerves. Having enveloped this portion of the vertebræ with
a piece of sheet lead, with one end of a metal conductor, I
touched the coated part, and with the other the surface of
the thighs, which had been previously stripped of the skin.
The movements were violent, and continued for a long time,"
&c. In general, throughout the whole of this physician's
expertmental treatise, when one or more of the nerves of an
animal are coated with sheet-lead or any other metal, that
animal is said to be prepared.
to 
 

222 APPENDIX.
a prepared frog by a hook with one hand, so as
to let its feet rest upon the bottom of a small sil-
ver cup, which he happened unintentionally to
strike with the other; at the instant the body of
the animal fell into violent convulsions. If one
person held the prepared frog, and another touch-
ed the cup, no movements were excited. The
professor being now aware of the necessity of a
communication, undertook a series of experiments
for the farther investigation of this subject. He
first placed a prepared frog upon a non-conduct-
ing surface, and brought one end of a conductor
in contact with the hook which secured the ani-
mal, and with the other touched its feet, on which
the contractions took place. When the conduct-
ing arch was interrupted by a non-conducting
substance, the frog remained motionless, &c."
No sooner had professor Galvani published to
the world his experiments on animal electricity,
than their same dispread, swift as the intangible 
fluid which they regarded, throughout the differ-
ent parts of Europe. Animal electricity became,
in a short time, a subject of very interesting specu-
lation to medical philosophers. Among the seve-
ral physiologists who entered the lifts in this in-
vestigation, the most distinguished whose writings
have fallen into my hands, are Dr. Valli, an Italian
physician, from whose publication the preceding
account

223 APPENDIX. 
account respecting the first discoveries of Galvani
is extracted, and Mr. Fowler, a native of the
island of Great Britain.
Doctor Valli appears to have led the van of
those philosophical characters who first co-ope-
rated with the celebrated Galvani in investigating
that animal fluid, the existence of which had been
so long suspected, but so lately realised by actual
experiment. After repeating most of the experi-
ments of his predecessor in this branch of physics,
the Doctor proceeded to a series of new experi-
ments, mostly conceived and instituted by himself.
The objects which he appears to have kept stea-
dily in view throughout the whole course of his
experiments and observations were, to ascertain
the nature of the animal fluid discovered by the
professor of Bologna, and to determine its influ-
ence and medium of operation in the animal eco-
nomy. In the prosecution of these ends the Doc-
tor has doubtless displayed all that industry and
patient perseverance, so essentially requisite in the
character who would successfully inquire of na-
ture, through the medium of experiment. I am
sorry, however, to observe, that all his experiments
were not conceived and instituted with equal in-
genuity, and perhaps I may add, not executed
with equal accuracy and definitude. Many of
many 

224 APPENDIX.
them appear to have been instituted without a di-
rect reference to any specific or particular end—
Equally unhappy with regard to conception, inde-
finite with respect to their nature, and inconclu-
sive in point of result, they leave no impressions
on the mind of the reader, save those of disap-
pointment and regret—regret that a character of
such learning and industry should, notwithstand-
ing, interrogate nature with so little meaning, and
(I am sorry to add) with so little success.
The preceding observations must be considered
only in the light of general rules, and as such,
are liable to numerous exceptions. Many of the
experiments of Dr. Valli are, doubtless, both in-
genious and valuable; and I even entertain the
utmost confidence, that the period will yet arrive,
when the whole of them, that are ascertained
and related with justness and definitude, will be
made subservient to the establishment of general
and useful results. At present, however, they
stand in an insulated state, completely detached
from practical conclusions, and disconnected from
all known principles in physical science.
After a series of experiments sufficiently lengthy
and tedious, the Doctor conceived himself une-
quivocally authorised to conclude, that the animal
fluid of Galvani, was entirely the same with the
4 subtle 
 

225 APPENDIX. 
subtle matter of electricity. This conclusion he
alleges to be the spontaneous and necessary result
of the following positions, which he delivers as
substantiated and confirmed by actual experiment.
" First, substances which conduct electricity,
are conductors likewise of the nervous fluid."
" 2dly, Substances which are not conductors
of electricity, do not conduct the nervous fluid."
" 3dly, Non-conducting bodies, which acquire
by heat the property of conducting electricity,
preserve it likewise for the nervous fluid."
" 4thly, Cold at a certain degree, renders water
a non-conductor of electricity, as well as of the
nervous fluid."
" 5thly, The velocity of the nervous fluid is,
as far as we can calculate, the same with that of
electricity."
" 6thly, The obstacles which the nerves, under
certain circumstances, oppose to electricity, they
present likewise to the nervous fluid."
" 7thly, Attraction is a property of the electric
fluid, and this property has been discovered in the
nervous fluid."
VOL. II. P Having

226 APPENDIX.
Having enumerated and detailed the foregoing
arguments, the Doctor, in an effusion of triumph,
subjoins, " We here see the greatest analogy be-
tween these fluids; nay, I may even add, the cha-
racters of their identity."
As an additional support to the same opinion,
Dr Valli adduces the peculiar and striking pheno-
mena exhibited by the torpedo, the gymnotus elec-
tricus, the silurus, &c. which proceed, as he
alleges, from a fluid in every respect the same
with that which was discovered in frogs, by the
professor of anatomy at Bologna. As the Doctor,
however, has advanced nothing in confirmation of
such entire sameness, save a certain remote analogy
which he says he has discovered between the mus-
cles of animals, and the electrical apparatus of the
torpedo, the gymnotus, &c. it is obvious that this
latter argument will but very slightly impress the
philosophical physiologist, who founds his belief
of principles on facts, rather than on vague and
visionary conjectures.
Having thus, as he supposed, satisfactorily ascer-
tained the identity of the nervous with the electric
fluid, he next proceeds to speculations on its in-
fluence in the diversified movements and functions
of the animal economy. To me, however, I must
confess, the greater part of this speculative inves-
tigation, appears to be rather the effervescent
effusions 
 

227 APPENDIX. 
effusions of an imagination, heated to excess in a
favourite pursuit, than the solemn decisions of a
tranquil and unbiassed understanding. I acknow-
ledge myself unable, in many instances, to discern
the necessary nexus or affinity between his con-
clusions, and the facts from which they are de-
duced:—or perhaps I may speak my sentiments
more fully when I say, that the learned author
appears not unfrequently to have substituted mere
hypothetical allegations, for fair and logical conclu-
sions—the vacant results of his own conjectures,
for genuine principles developed by experiment,
and ascertained by observation. It very often
happens, that by attempting to embrace too much
under a single cause, we extend the tortured
principle beyond its natural limits, and thus, to
appearance, weaken or render doubtful its influ-
ence, even on those phenomena which it immedi-
ately regards. This observation applies with too
much propriety and force, to the speculations of
the indefatigable Valli. By attempting to explain
all, he has in fact explained none, of the pheno-
mena of the animal economy, by that subtle fluid
on which he so patiently experimented. Many of
his physiological facts and speculations are indeed
ingenious and interesting, but, in my view, they are
equally deducible from any other series of experi-
ments, as from that by which they are preceded
in the Doctor's publication. Many of the learned
author's facts may be, no doubt, true and well
P2 defined 


228 APPENDIX.
defined, and some of his principles and results to
a certain degree interesting to the physician and
philosopher, but, taken in the aggregate, they
are too disjointed to constitute any thing like a
system, too disconnected to form a regular chain
of investigation. On my mind, his speculations
on the causes of muscular motion, sensation secre-
tion and nutrition, impress no more solid convic-
tion than do those of Stahl on the subject of his
anima medica, of Van Helmont respecting his
subtle Archeus, or of the airy Paracelsus with re-
gard to his planetary influence. Notwithstanding
the apparent severity of the foregoing observa-
tions, I am still obliged to declare it as my
opinion, that the novelty and importance of the
subject on which Dr Valli has experimented and
written, entitle his work to the particular atten-
tion of the learned and ingenious of every na-
tion.
For the want of system and requisite decision in
the writings of the preceding author, compensation
is, in a great measure, made by a subsequent pub-
lication of the accurate and ingenious Fowler. The
experiments and speculations of this young philoso-
pher, on what he terms, the " influence discovered
by Galvani," made their first public appearance
at Edinburgh, in the course of the year 1793:
they are not, indeed, so numerous as those of the
Italian physician, but they appear to have been
conceived 

229 APPENDIX. 
conceived with more design, and executed with
more judgment. Mr. Fowler seems to have been
among the first who controverted the opinion of
Galvani and Valli, respecting the identity of the
nervous and electric fluids: and he has, doubtless,
controverted it with ability and effect.
Mr. Fowler preliminates his observations, with
a lucid and forcible statement of a certain previous
combination of circumstances, which he alleges,
must have strongly prepossessed the mind of professor
Galvani, with a belief of the sameness of the pre-
ceding fluids.
That such a prepossession must have had, indeed,
a powerful effect on the subsequent deductions and
conclusions of the Professor, will be readily ac-
knowledged, by every one who has experienced
the influence of preconceived opinions—an influ-
ence pregnant with error, and leading countless
evils in its train.
Mr. Fowler proceeds then to mention the first
object which engaged his attention, in the com-
mencement of his interesting inquiry, and which
appears well calculated to pave the way, for the
more easy and effectual accomplishment of his
experimental course. This, to make use of his
own words, was, " to ascertain, as well the va-
P3 rious 


230 APPENDIX.
rious circumstances, essentially requisite to the
production of these new phenomena, as those in
which they can be rendered most obvious." The
issue of his enquiry on this subject, I will also lay
before the reader in his own words. " After "
says he, " a great variety of experiments, of which
it would be unnecessary here, to relate more than
the result, I found, that I could not excite in an
animal the appearances described by Galvani, with
any substances whatever, whether solid or fluid,
except the metals: and that the mutual contact of
two different metals with each other, so far as I
was able to determine, was in every case necessary
to the effect."
After a satisfactory attainment of this object,
the ingenious author next proceeds to a judicious
series of experiments, with a view to discover the
genuine nature of the animal fluid, first realised by
the fortunate professor of Bologna. Of those ex-
periments he does not give us a minute specifica-
tion, but only furnishes statements of their most
obvious and striking results. These statements he
also occasionally intersperses with interesting and
important remarks, and some very ingenious spe-
culations.
Having finished his series of experiments, (a
series sufficiently numerous and diversified for the
establishment 

231 APPENDIX. 
establishment of general principles) relative to the
nature of the nervous fluid, and its affinity to the
matter of electricity, Mr. Fowler at length favours
us on this subject with the following conclusions,
which I shall take the liberty of presenting to the
reader in the words of their ingenious anthor.
After having stated a few analogies between the
animal fluid of Galvani, and that possessed by the
torpedo, he then reverses the comparison, and
lays down several points of essential difference,
not only between the two preceding fluids, but
also between the former of them, namely the fluid
of Galvani, and the matter of electricity.
" This influence, (says he, referring to the
nervous fluid of animals) differs, both from that
of the torpedo, &c. and from electricity, in pro-
ducing no sensation (in man at least) at all similar
to that of an electrical shock."
"—That some kind of disagreeable sensation
is occasioned by it, even in frogs, independent of
that which must necessarily arise from irritation
and the contractions of their muscles, is evident
from their restlessness and expressions of uneasiness.
In other animals, as I shall afterwards have occa-
sion to shew, these expressions are still less equi-
vocal: and in man we can ascertain both their
P4 degree 


232 APPENDIX.
degree and their kind. That they differ consider-
ably from such as are produced by electricity will
be proved when I come to speak of the effects of
this influence upon our senses."
" But the most important, and characteristic
difference which I have yet been able to discover,
between this new influence and electricity, consists
in their effects upon the contractile power of
animals and of plants. The contractions of ani-
mals excited by electricity have a tendency to
destroy that power upon which contractions de-
pend. But the contractions excited, by the appli-
cation of the metals, have, in all my experiments,
had the directly opposite effect. The more fre-
quently contractions have been in this way excited,
the longer do they continue excitable: and the
longer are the parts upon which such experiments
are made, preserved from putridity. An influ-
ence, capable of exciting contractions without
occasioning exhaustion, was a thing I so little
expected to find, and so contrary to the character
which had been given of this both by Galvani
and by Doctor Valli, that I at first distrusted my
own observation of the fact: but the number of
comparative experiments which I had afterwards
occasion to make, though with views different
from that of ascertaining the point in question,
convinced me that this influence, so far from
destroying 

233 APPENDIX. 
destroying the contractility of muscles, has a ten-
dency to preserve it. Oxygene is, so far as I
know, the only stimulus in nature, whose effects
are at all analogous."
" When a frog has been long dead, I have
been sometimes more than a quarter of an hour
without being able to excite a single contraction
by the application of the metals: but after this,
without at all varying the means employed, con-
tractions have appeared, and have become gradu-
ally more and more vigorous."
" It is said (for I have never had an opportunity
of making the experiment), that a stream of elec-
tricity, passed through a sensitive plant, produces
an almost immediate collapse of its leaves. But
the influence discovered by Galvani produced no
such effect in the following experiment. Having
separated the leg of a frog from its body, I freed
its crural nerves from surrounding parts, and with
one hand held it supported upon the end of a
probe. An assistant placed a piece of silver under
its foot, and held the zinc with which it was to
be touched. A sensative plant formed the medium
of communication between us. He held the bot-
tom of its stem between his fingers, while I held
the top; so that when the silver was touched by
the zinc, the influence passed up the plant, and
through 

234 APPENDIX.
through the whole of its stem. The frog's leg
instantly contracted, and repeated its contractions
every time the silver and zinc were brought in
contact: but the leaves of the plant did not col-
lapse; neither did they when any of its branches
formed part of the circuit."
I must however, confess that the plant, upon
which this experiment was made, had been kept
through the winter. With a young one the result
might possibly be different; but such an one I
have not yet had in my power to procure.
" The torpedo does not appear at all affected
by the influence which itself produces. Animals
in which Galvani's phenomena are produced, are
strongly affected."
The very ingenious author passes on next to
report the result of certain experiments which he
instituted, in order to refute the opinion of those,
who allege, that the fluid of Galvani proceeds
entirely from the metallic substances used, and
does not reside at all in any part of the animal
system. In his enquiry respecting this point he
displays the same fertility in devising, the same
sagacity in judging, and the same ingenuity in
deducing, which so forcibly impress the reader
throughout every part of his experimental investi-
gation. 

235 APPENDIX.
gation. He also farther shows, that the nervous
influence of Galvani, and the subtle fluid of elec-
tricity differ very materially from each other in
the following particular, namely, that against the
effects of the former, animals are able to guard
themselves by means of a certain voluntary exer-
tion, whereas the operation of the latter is not in
the smallest degree subject to the controul or in-
fluence of the will.
Having finished the consideration of the nature,
Mr. Fowler proceeds to make some useful appli-
cations, of the influence discovered by the professor
of anatomy at Bologna. In his attempts to shed
light on certain controverted points, and to solve
certain abstruse questions, in physiology, by means
of this fluid, he appears no less ingenious and
satisfactory than in the former parts of his
enquiry.
He appears peculiarly happy and conclusive in
his researches after the source from whence the
nerves and muscles derive their respective powers.
I beg leave to lay before the reader two of the
author's experiments, instituted for the purpose of
ascertaining this interesting particular—a particular
which has so long furnished a subject of contro-
versy among speculative physiologists. The latter
of the two experiments, (to which the former
serves 

236 APPENDIX.
serves only as a necessary introduction) is of itself
more than equal to all that has ever been ad-
vanced on the opposite side of the question.
EXPERIMENT I.
" I divided (says Mr. Fowler) the sciatic nerve
of one leg, and tied the crural artery of the other
in a large frog. Scarcely any blood was lost in
doing either. Two days after this I strangled it.
During the first 24 hours, the leg in which the
nerve had been divided, appeared to contract with
the most vigour; after this period the difference
between them became more doubtful; but the
contractions were at no time stronger in the leg
whose artery was tied, than in that whose nerve
was divided.
EXPERIMENT II.
" The same operations were performed upon a
large female frog full of spawn. Four hours
afterwards she was covered by a male, who had
been treated in a similar manner. I mention this
circumstance, as it tends to prove, that the pain
occasioned by the operation was probably not so
great as to produce much fallacy.
" On the day following, she had spawned, and
on the sixth day from the operations, she was
strangled. When laid upon a plate of zinc, and
excited 

237 APPENDIX.
excited by means of a rod of silver, the contrac-
tions were found extremely feeble in the leg
whose artery had been tied, and ceased altogether
in about twenty-two hours after her death.
In the leg, whose nerve had been divided, they
appeared as vigorous as they usually are in legs
to which no injury has been previously done, and
continued excitable upwards of two days after
they had ceased to be so in the other."
It may be proper on the present occasion briefly
to observe, that the influence discovered by Gal-
vani was the test used by Mr. Fowler to determine
the existence or cessation of irritability in the
muscles of the animals subjected to the preceding
experiment. For this influence, as our author
judiciously observes, appears to be indeed by far
the best and most delicate test that has ever yet
been discovered for ascertaining the lowest possible
degrees of muscular irritablility. After having
become wholly insensible to the impressions of all
other stimuli, muscles still continue to vibrate to
the kindred touches of this subtle fluid, to which
nature appears to have given them such a nice,
and, perhaps I may say, specific correspondence.
Mr. Fowler, after having transiently glanced
on the subject of inflammation, passes on to the
attack 

238 APPENDIX.
attack of a physiological doctrine, propagated with
zeal, and supported with ability by that celebrated
experimentalist, the Abbe Fontana. The doctrine
alluded to, embraces the existence or residence of
a certain vital principle in the volume of the
blood. On this principle, as the industrious
Abbe alleges, poisons produce their instantaneous
effect, when introduced into the vascular systems
of living animals. To all the different parts of
this physical doctrine I could never yet be induced
to subscribe, notwithstanding the respectability of
its learned and numerons advocates.
By attacking and vanquishing one of its most
powerful champions, Mr. Fowler has doubtless
contributed much to its final demolition. For, in
the contest now under our immediate conside-
ration, I must confess, that to me the laurels of
victory appear to be fairly wrested from the
silvered temples of the Italian, and planted over
the youthful brow of the British Philosopher.
I have thus exhibited a view, somewhat general
indeed, though confessedly very succinct, of the
results laid down, and of the opinions entertained,
by the ingenious Fowler, on the subject of the
animal influence discovered by Professor Galvani.
To lay before the reader a full account of all that
is useful and important in the observations of this
interesting 

239 APPENDIX. 
interesting author, would be to transcribe and re-
print his whole publication.
The only productions in the English language,
which this country now furnishes, professedly on
the subject of the animal fluid discovered by Gal-
vani, are (as formerly observed) those of Fowler
and Valli. On the comparative merit of those
two authors I will here take the liberty of
advancing a few general, and, I flatter myself,
impartial, observations:
The experiments of Doctor Valli are more
numerous and pompous—those of Mr. Fowler
more definite and intelligible. The former author
appears often, the latter, never, to have experi-
mented without some determinate end in view.
The experiments of the Italian may be compared
to the promiscuous plants of the forest, strewn at
random by the sportive and irregular hand of
nature—those of the young Briton, to choice and
valuable collections, arranged with order and
elegance, in a well regulated and beautiful garden.
The experiments of Valli appear to throw into
shade, those of Fowler into light, the objects
which they immediately regard. From the for-
mer, the reader collects information with diffi-
culty, from the latter, without labour or painful
attention. 
In

240 APPENDIX.
In their deductions and speculations, the two
preceding authors are no less dissimilar, than with
regard to their experiments themselves. Valli is
more diffuse and often hypothetical—Fowler more
pointed and generally conclusive. Valli appears
to give loosened reins to a glowing imagination—
Fowler to be constantly under the steady guidance
of a powerful and well-cultivated understanding.
The former makes a greater display of learning,
and, therefore, too frequently views objects
through the more obscure media of previous
publications—the latter exhibits a higher degree
of ingenuity, and derives the principal part of his
information, not from pages, sanctioned only by
the names of celebrated, yet fallible, authors, but
from the great folio-volume of nature, impressed
with her own signature. On the whole, Valli
has experimented and written in the most lengthy
and profuse—Fowler in the most definite and
conclusive manner. In many parts of the writings
of the former, nothing else than the fiat of an
almighty genius would be able to bring order out
of confusion—in those of the latter, lucidity, con-
nection, and regularity, shine pre-eminent through
almost every page.
Having thus, without reserve, delivered my
sentiments on the publications of others, I hope I
may be allowed to trespass on the reader's attention
4 while

241 APPENDIX. 
while I make a few observations relating to my
own.
Nothing could have induced me thus hastily to
forsake the humble, but secure, retreats of obscu-
rity, and risk myself before the eye of the world
in the hazardous character of an author, save a
solicitous wish to contribute to the advancement
of medical science, and thus aid in acquiring for
man a more effectual exemption from misery and
pain. I saw with regret the literary treasures of
a Blumenbach concealed from the view of my
fellow-citizens beneath the drapery of an ancient
and an obsolete language. I was anxiously
desirous to see the physiological system of that
illustrious character completely clothed in the
language of my country. I engaged in the trans-
lation of this work, not because I conceived my-
self better qualified for its execution than others,
but because others appeared to me unpardonably
remiss with regard to the undertaking. The
execution proved laborious and difficult beyond
my expectations. The difficulty of detecting an
author's precise meaning through the dusky
medium of a Latin expression, can be fully under-
stood and realised only by him who has made the
arduous experiment.
VOL. II. Q Even 


242 APPENDIX.
Even after the ideas and opinions in the original
are fully embraced and completely comprehended,
another difficulty of no small magnitude still
remains, namely, to convey them to the reader
with unequivocal definitude, through the indefinite
medium of a different language. It is well known
how extremely liable we are to misapprehend the
precise meaning of an author who even writes in
our own vernacular tongue, much more so of one
who publishes in a language but little used in con-
versation, and, at best, but imperfectly understood
by any man living.
Should the foregoing translation ever fall into
the hands of the celebrated professor of Geottingen,
I hope he will receive, with candour and indul-
gence, a well meant attempt to extend the empire
of his utility and his fame, by increasing the
number of his admiring readers. If the transla-
tion be in any part erroneous, in any part defi-
cient, strictures and corrections will be thankfully
received, and punctually attended to in a second
edition of the work, should a second be demanded
by a patronising public.
To preserve as far as possible the firm and
energetic spirit which characterizes the writings
of the illustrious professor of Goettingen, and to
convey 

243 APPENDIX.
convey to my readers the facts, the principles, the
speculations, and the opinions contained in his
original work, without even the shadow of altera-
tion, diminution, or addition, has been my steady
and uniform aim throughout the whole of the
foregoing translation. Owing, however, to the
different constitutions or idioms, as they are more
generally termed, of the Latin and English lan-
guages, my translation is in many places far—very
far from being strictly literal. Phraseology I con-
sider, at best, as the mere trappings or drapery of
composition, while facts and principles constitute its
more substantial and important part. To preserve
the latter, therefore, inviolate, and to communicate
them with the utmost definitude, is the indispen-
sible duty of a translator, from a principle of
justice to the original author, to the public, and
to himself; but in my opinion, he is not bound,
by any principle whatever, to make an entire
sacrifice of all elegance and beauty, to mere puncti-
lious literality of expression. Impressed with the
propriety and truth of these sentiments, I have,
throughout the whole of the foregoing work,
been sometimes literal and sometimes free,
accordingly as the one or the other mode of
translation gave birth to a phraseology or stile
most agreeable to my ear, and most accordant to
the spirit of the original composition.
Q2 With 

244 APPENDIX.
With respect to the appendix itself, it may not
be amiss to make it the subject of a few transient
observations. The principle which these additi-
onal pages regard, and are intended to commu-
nicate, is justly becoming, among medical philoso-
phers, an object of primary importance. This
principle opens to the view of the speculative mind
a rich and spacious field, never yet printed, save
by the adventurous steps of a few pre-eminently
active and enterprising physiologists—A field, the
salutary fruits of which will, no doubt, at a future
day, serve to elucidate the nature, to develope
the composition, and to alleviate the complicated
misery of man.
My whole design in this appendix is to give a
condensed, but somewhat general view, of this
principle or influence discovered by professor Gal-
vani.
By far the greater number of medical charac-
ters in the immense tract of country embraced
within the limits of the United States, are, in con-
sequence of their distances from literary institu-
tions, excluded from access to public libraries,
and situated quite beyond the free circulation of
physical science. To such my appendix will serve
the humble purpose of a literary chronicle; it will
convey to them a brief account of the discoveries
2 which 


245 APPENDIX.
which are now going forward in the delightful
and important science of physiology.
On the subject of the influence discovered by
Galvani I have myself instituted and performed
a considerable number of experiments *; some of
* That the reader may be acquainted with an easy, cheap
and familiar method of experimenting on this subject, with-
out having his feelings hurt by the agonizing pangs of tor-
tured and dying animals, I will here take the liberty of in-
serting, in form of notes, a few extracts taken from a com-
munication transmitted to Mr. Fowler, by his learned friend
Mr. Robison, professor of natural philosophy in the univer-
sity of Edinburgh.
I. " I find (says the professor) that if a piece of zinc be
applied to the tongue, and be in contact with a piece of sil-
ver, which touches any part of the lining of the mouth,
nostrils, ears, urethra, or anus, the sensation resembling taste
is felt on the tongue. If the experiment be inverted, by ap-
plying the silver to the tongue, the irritation produced by
the zinc is not sensible, except in the mouth and the urethra,
and is very slight.
II. " If the zinc (finely polished) be applied to the ball
of the eye, the brightness of the flash seems to correspond with
the surface of contact of the silver with the tongue, palate,
sauces, or cheek. The same thing happens when the silver
is applied to the eye."
III. " When a rod of zinc and one of silver are applied
to the roof of the mouth, as far back as possible, the irrita-
tions 
 

246 APPENDIX.
my results have appeared striking and new, but my
experiments have been neither sufficiently nume-
rous nor varied to warrant the deduction and esta-
blishment of general principles. My present in-
tention is (should heaven indulge me in life and
health), to prosecute to some extent this highly
tions produced by bringing their outer ends into contact, are
very strong, and that by the zinc resembles taste, in the same
manner as when applied to the tongue."
IV. " I had been paring my toe-nails with scissars, and
had cut off a considerable portion of the thick skin, so that
the blood began to ooze through in the middle of the wound.
I applied the zinc there, and an extensive surface of silver
to the tongue. Every time I brought the metals into con-
tact, I felt a smart irritation by the zinc at the wound," &c.
A variety of other experiments of a similar nature are
contained in the same communication from Mr. Robison
to Mr. Fowler; but a further detail of them I conceive un-
necessary, as the ingenious reader, being acquainted with
the foregoing, can with facility devise other experiments
for himself. Thus I have frequently conveyed to my eye
the luminous flash mentioned by Mr. Robison, not only
from the internal vestments of the mouth, the nose, the ure-
thra, &c. but also from between my fingers, from the cu-
bital flexure of my arm, and from various other parts of
my body, where the texture of the cuticle and skin is more
fine and soft than ordinary; always taking care, however,
to moisten the part previously to the application of the
metals.
interesting 


247 APPENDIX.
interesting subject. Should my investigation be
favoured with the discovery of any thing curious
in science, or useful in practice, a detail of it may
be expected in a future communication.
To my solemn audit before the bar of the pub-
lic, I now hasten in tremulous anxiety, " with all
my imperfections on my head,"—imperfections
which will no doubt awaken the censure of the
critic, but receive, I flatter myself, the indulgence
of the liberal and candid. The approbation of
the former I neither court nor regard; that of
the latter it shall be my constant ambition to de-
serve. The professed business of most modern
critics appears to be, to condemn—promiscuously
condemn, too frequently without the faintest sha-
dow of either inclination or talents to discriminate
merit from its reverse.
In my view the approbation of a professed critic
is perfectly synonymous with the censure of the
liberal and the ingenious, to whose candid exami-
nation the preceding pages are submitted with all
that respect and deference due from an inexperi-
enced writer.
THE END.