TEXT  BOOK
OF A
Couvor of  acctitres,
ON THE
THEORY AND PRACTICE OP PHYSIC.
FART FIRST.
By JAMES JACKSON, M. D.
FOR THE USE OF THE MEDICAL STUDENTS



    OF HARVARD UNIVERSITY

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1 uc~ on.
                     in.

                   :7V /
BOSTON
WELLS AND LILLY—COURT-STREET.


         1825.
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INTRODUCTION.
The Science and the Art of Medicine are confess-
edly imperfect; yet so great is  the  amount  of
knowledge possessed by the world, if we take  all
which could be gathered from those, who practise
the art, and so  numerous are  the  details, into
which  that knowledge would carry us, that pro-
bably there  are  very  few men,  who know half
that is  known  of  this science and this  art.  Al-
though  one man  may know* more than any other,
yet that man is probably deficient in  many points,
on which others are well informed.  No man then
can be  considered qualified to teach the whole of
this science and art.  But it is  obvious that the
fullest time usually allotted to a course of lectures
must be vastly too short to communicate all, which
 one man of common talents and  common industry,
 must have  acquired in a  few years  only devoted
 to the  study and practice  of medicine.  Every ex-
 pedient, therefore, which can  help  the teacher,
 should  be adopted.
   The advantages in giving instruction by lectures
 on medicine and  similar  subjects, where  there is 
4>
TEXT BOOK.
 not any demonstration nor experiment, must  con-
 sist  principally in the stronger and  more lasting
 effect produced  by impressions on  the mind  con-
 veyed through the  ear,  than  by those  conveyed
 through the eye.   But these advantages cannot be
 secured, except  great method  and  distinctness be
 observed  in  the  oral statements.  The greatest
 difficulty to  the hearer  is to  keep in mind  the
 method, which is laid down.  Likewise in listening
 to the details of evidence in support of one propo-
 sition, the hearer is liable to forget the train of
 propositions, with which  it is connected.  To ob-
 viate these difficulties we must avail  ourselves of
 the eye and the ear at the same time.   This may
 be done by  the use  of a syllabus, or of a  text
 book placed in the hands  of  the pupil.
   In  the year 1816  I prepared very hastily,  and
 amidst many pressing  engagements,  a  syllabus for
 my course of  lectures. Imperfect  as  this  was  I
 have  reason to believe that it has been  useful to
 those, who have attended  me.  As however  the
 edition  then  printed is nearly  exhausted, it was
 proper for me to think in  what way I could render
 this little volume more perfect.   And  on full con-
 sideration it has appeared to me expedient to pre-
 pare a text book in preference to a syllabus.  Since
 the establishment of  the  Hospital in this place  I
 have  been able to  carry my pupils  to visit  the
 patients in  this excellent Institution and have there
given  them clinical instructions.   But  the pupils, 
INTRODUCTION.
5
engaged in attending courses of lectures on other
branches of medicine, have found it as difficult as
I have to  spend the  time necessary to visit  the
Hospital,  without giving up  some  of the hours
formerly devoted  to the lectures  on the theory
and practice of physic.  Hence I  have been com-
pelled to  shorten my course on this last subject.
This  difficulty may I conceive be  diminished, if
not obviated, by a text book.  For not only in
that much may be read,  which would  otherwise
be stated in the lecture  room in more words;  but
the method of the discourse and the most important
propositions being  always before the  eye, there
must  be less occasion for repetition and recapitu-
lation than there would be otherwise.
  It  must however be   remarked that a  text
book, as  well as a  syllabus,  need not be equally
precise, nor equally full on all subjects.  In this
respect I shall be governed by considerations of
expediency.   Thus  in the part,  which relates to
physiology, so far as that division of the science is
discussed in my lectures, it seems to me proper
that the  text book  should be more  full  than in
those parts, which  relate  to pathology and thera-
peutics.
   The  science  of  medicine  admits of four great
divisions, physiology, hygiene, pathology and  thera-
peutics.   Each of these, in a  full discussion of the 
6
TEXT BOOK.
 science, should be  considered separately.   But it
 is not  convenient  to describe each disease  under
 pathology, and then 10 introduce the same again
 under  therapeutics in  order  to  state the mode of
 cure.  It will be more convenient to consider the
 general principles of the science under these divi-
 sions, and then to describe separately diseases and
 the  treatment  adapted  to them.  This  separate
 description of diseases and their treatment I shall
 denominate the practice of medicine.
   As time will  not permit me to treat of hygiene
 in my winter course, addressed  to  medical pupils,
 although it constitutes the principal subject of the
lectures delivered to the under graduates of  the
University, I shall not at present prepare  the part
of my  text book relating to  that division of  the
science.
   In this place I wish to make  some observations
on the first division,  physiology, in order to show
the  extent of this division of the  science and  to
show how small a part of it will be considered in
this  course.
  In a full and systematic view of physiologv the
following objects  should  be regarded.   l/The
structure of the various parts of the human body ;
—the simple textures, the organs into which these
enter, and the  physical  properties  of  the fluids.
II. The  chemical  composition  of  these various 
INTRODUCTION.
7
parts.   III. The vital properties.   IV. The func-
tions of the various textures and organs.  V. The
growth of the whole body and the occasional de-
velopement of particular  parts.  VI. The varie-
ties of the human race, viz. those of sex, race and
temperament.  VII. The relations existing between
the living system and external things.  VIII. Death,
or the modes  in which life terminates.
   Some of these topics are  discussed  in distinct
courses of lectures.  The structure of the body
and the functions of its various organs are the sub-
jects of the anatomical course ;  and from the diffi-
culty of obtaining a good acquaintance with these
subjects,  as well as  from the  fundamental  impor-
tance  of them,  they  well deserve  to constitute
a distinct branch of study.   The  composition of
the various animal  solids and  fluids  constitutes  a
part  of the chemical course.   The consideration
of the other  topics might be  entered upon  with
sufficient  propriety in the lectures on  the  theory
and  practice of  physic.   But  the  period  allotted
for this course will not allow full attention to these
objects without a neglect of things more  import-
ant.    I  therefore introduce  under  the head of
physiology such  topics only as  are subservient to
the subsequent parts of the course.
   It is the especial object of the physiological part
of my course  to point out what pertains  to  the
subject of vitality.  As the most brief and conve- 
8
TEXT BOOK.
nient way of doing this I shall describe in a gene-
ral way the functions  common  to  all  organized
living beings, and then the vital powers or proper-
ties, which  are displayed in the performance of
these functions.   The  same plan  will  then be
pursued in respect to the functions and vital pro-
perties  peculiar  to animals.  Next  the mutual
relations between the different organs will be stat-
ed ;  and afterwards the relations  existing  between
the  living human  system  and  external things.
Lastly, death, or the  modes  in which life  termi-
nates, will be described. 
PHYSIOLOGY.
  I. Every  organized living being is an integral
being,  a  whole  by itself.   It  bears relations  to
things  external to itself; but it does not, in its per-
fect state, immediately depend on any one indivi-
dual external  thing for the performance  of  its
functions  and  the  maintenance  of  its  life.   Its
powers depend only on the being who gave them.
  II. There are  three  kinds  of functions, which
are  performed  by all organized  living beings.
These  are those  of  assimilation, formation and
EXCRETION.
  III.  Every organized living being  requires sup-
plies from without, although not dependant on any
individual  portion of  matter  for those  supplies.
Every  such  being receives  these   supplies and
changes the  materials to a fluid* fitted to furnish
both the other fluids  and the  solid organs neces-
sary to its existence.  This is assimilation.
  IV.  The organization, by  which the functions of
assimilation are performed, is in some beings more,

  * If this proposition be couched in terms too general it will
at least  be admitted  in respect to those  animals and vegeta-
bles, whose economy is best known to us.
          2 
10
TEXT BOOK.
in some less  complicated.   The organs, by which
the food is received, perform  a function subordi-
nate to those of assimilation, and may be regarded
as belonging  to the organs of assimilation.
   V. In plants the food is first received by absorb-
ing vessels, principally in the roots.  These vessels
are continued into others,  which pass through the
leaves and returning are distributed to the  various
parts of the  plant.  The material  in the vessels
passing from the roots to  the leaves is called sap;
that in the vessels passing from the leaves is called
succus proprius, and  consists of the food now en-
tirely assimilated.  Something appears to be  thrown
out from the leaves; and although it is not cer-
tainly known, yet it is highly probable  that some-
thing is added there to the materials in the  vessels.
If any thing  is  added, this is  still derived  from
without by absorbing  vessels,  analogous in  their
general character to those of the roots.
   VI. Hence it appears that the food is assimilated
in plants while passing through vessels, which are
analogous to  the large  blood-vessels of the human
body; vessels to which may be  given the general
names of carrying and  distributing vessels.  Accor-
dingly, whatever change, is wrought in  the  food in
producing the succus proprius, that  is, in the func-
tions  of  assimilation, must  be  attributed  to the
influence of the carrying and distributing vessels.
   VII. In animals the  organization, necessary for
the functions  of assimilation, appears  to be more 
PHYSIOLOGY.
11
complicated than in vegetables, or plants.   In the
latter the food is taken  up in  small  particles  by
numerous vessels.    In animals generally,  if not
universally,  there is  an organ  called a  stomach.*
This varies  in different animals, consisting of more
parts in some than in  others;  but  it may be  re-
garded as a large vessel, into which masses of food
may be received and  in which  this food  is partial-
ly assimilated.   In the more perfect animals there
are connected with the stomach certain subordi-
nate organs, each of  which prepares  and  pours
into it a peculiar  fluid, or aids it  in some other way.
Of the materials received into  the stomach, a por-
tion is discharged from it, without having been as-
similated.
   VIII.  From the stomach  there  arise  absorbing
vessels analogous  to those of plants, and  these
vessels are continued into the  carrying and distri-
buting vessels.   The absorbing vessels, which arise
from the stomach in  the more perfect animals, are
called lacteals.   The vessels, into which they are
continued, are called blood-vessels.
   IX. That part of  the food,  which is  taken up
by the lacteals, is called chyle.   This, after  it has
been received into the blood-vessels, is changed in
its properties  and is then  called blood.  Thus  it
appears that in animals assimilation is commenced
in the stomach and is perfected in the blood-vessels,

   * The word stomach is here used in its most extensive and
general sense and is equivalent to the words alimentary canal. 
12
TEXT BOOK.
   X. The food, after  assimilation, both in  plants
and  animals, is  in a fluid state.   This  assimilated
fluid always differs in its properties from the crude
food, from   which  it  is derived.   The  change
wrought in its  assimilation cannot be attributed to
any  mechanical process; nor can it be attributed
to any such  chemical process, as can be effected out
of the living body.  The affinities, by which the ele-
ments of the assimilated fluid  are united,  are not
those which operate, when the same particles are
brought together out of the  living body.   Those
affinities may therefore be called vital  affinities, in
order to distinguish them from those affinities which
exist in dead matter and which  are called chemi-
cal affinities.  These vital affinities must  be com-
municated by the living organs, through which the
elements possessing them have passed ; since these
elements are exposed to no other agent.
   XI. The  assimilated  fluid  in living organized
bodies is  used  for the formation of  the various
solid parts, or organs of such  bodies, and for  that
of the secreted fluids employed  in  the various
functions of the same.  To this  use  it is applied
by vessels continuous with the carrying and distri-
buting vessels;  though generally  the former are of
less  size  than the latter.  The  vessels employed
in this application  of the assimilated fluid may be
caUed formative vessels.
  XI1. The functions of the formative vessels are
exceedingly similar in their character to those of
the assimilating vessels.  They receive a  certain 
PHYSIOLOGY.
13
material and they discharge a  material, possessing
undoubtedly the  same  elements,  but  differing  in
composition and other  properties.   Whatever dif-
ference there  is between the solids or liquids form-
ed and the assimilated fluid, must be attributed  to
the influence of the formative vessels ; for to these
alone  the  materials  in  question  are  exposed.
And this influence of the  formative vessels must
be owing to the  vital  powers of those  vessels ;
since the effects are not consistent with any laws
operating in dead matter alone.
   XIII.  The  evidence, that the formative vessels
exercise the influence attributed  to them, will not
probably be disputed.   But it should  be distinctly
remembered that the  kind of influence exercised
is known only by  the effects.   The action  of the
vessels is not  the  subject of any of our senses, and
there is nothing performed by one portion of dead
matter on another, by which  it can be illustrated.
We may be able to show  what  the action, or  in-
fluence of these  vessels is  not; and thereby ascer-
tain in some measure what it  is.
   XIV. In the more perfect  animals at least, as
in man, the stomach rejects, or discharges a certain
portion of the food received, without employing
it in the formation of the  assimilated fluid.  The
matter thus discharged is  called an excrement and
the  function  is denominated  excretion.  This  ex-
crement from the stomach, or first passages is, in
the  more perfect animals,  mixed with  the fluids 
14
TEXT BOOK.
 poured into those passages  by the subordinate or-
 gans, such as the liver, and by the formative  ves-
 sels, which terminate in  the coats of those passa-
 ges.   Thus the excrement  from  the stomach, or
 alimentary canal is  composed in part of materials
 derived from the blood, or assimilated fluid. These
 materials do not  appear to  be  poured  into  the
 alimentary canal merely for the purpose of excre-
 tion, but to subserve in some way the purposes of
 that canal.
   XV. There   are  other fluids  discharged from
 every  living organized body, some  in a liquid  and
 some in  a gaseous  state, which  have previously
 constituted properly a  part  of  such  body,  and
 which  are  at length  separated for excretion alone.
   XVI. It would seem that  the  materials, which
 constitute the organs of living bodies, are incapa-
 ble of  constituting parts of those  bodies beyond a
 definite period; and that that period is  less by
 much  than the ordinary period of  existence of
 such bodies themselves, as wholes.  The particles
 of such bodies  are therefore  taken  up by vessels
 very similar to  those, which  take up  the  food to
 be carried  into  the body.  The name of absorbing
 vessels  is  therefore  given to the vessels,  which
 take up these particles.  It  is not improbable that
 in vegetables and the  simplest animals these  ab-
 sorbing vessels connected with the excreting system
terminate in other mouths, by which they discharge
at once the materials they have taken  up.  In the
 more perfect animals however it is not so. 
PHYSIOLOGY.
15
  XVII. In  these  animals the absorbing vessels,
last described, terminate in the same blood-vessels,
which receive the  supplies from  without for  dis-
tribution.  Thus the blood, contained in  the distri-
buting vessels, consists of  a heterogeneous  mass,
viz. the chyle or imperfect blood, the blood per-
fectly assimilated and the waste brought from the
various parts for excretion.
  XVIII. To relieve themselves of the waste mat-
ter thus brought into them, the blood vessels are
continually   pouring  out   excrementitious  fluids
through different  organs, viz.  the kidneys, skin
and lungs.   The vessels,  by  which these excre-
tions are discharged from the  blood, are  continuous
with the blood vessels, and may be called the ex-
creting vessels.  The materials  discharged are no
doubt selected by these vessels, in some mode, from
the purer parts of  the blood ; and these materials
are so acted upon by the excreting organs  as to
be brought into a state fitted for  excretion.   The
excrements  from  the skin  and from  the lungs
are ordinarily discharged in a gaseous and insensi-
ble form, as are  those of plants.
   XIX. The statements  thus  far made  apply in
some measure to the functions of assimilation, for-
mation and excretion in all organized living beings.
The  organs common to all  appear  to  be vessels
absorbing at one extremity, and pouring out at  the
other for the purpose  either of formation,  or ex-
cretion; while  the intermediate portion of such 
16
TEXT BOOK.
 vessels, by which the absorbed  matter  is carried
 and distributed to the various parts, is of various
 length and in some beings more, in others less com-
 plicated as to form.  These vessels  in every  part
 appear to perform functions,  which they are  ena-
 bled to do only by vitality.
   XX.  It may now be well  to consider somewhat
 more fully the system of vessels,  which in  man
 and the more perfect animals serve  to carry and
 distribute the  blood  to  the various parts of the
 body.   In such  animals the  blood is  not  all used
 in the several  parts,  to which it is  carried at any
 one time, but is returned  in part for further use
 into the common mass.   This  is  effected by an
 arrangement of the vessels, by which the blood is
 made continually to circulate throughout the body.
 This circulation of  the  blood  and  the  changes
 wrought in the  blood during the circulation of it
 will now be  considered.   The  change of  chyle
 into blood has  already been stated, and  referred
 to the only possible cause, viz. the vessels in which
 it takes place.
  XXI. In the  more  perfect  animals there is al-
 ways a  quantity of blood, contained in its appro-
 priate vessels, more than is requisite for the imme-
diate purposes of formation.   This blood  is  made
to circulate by an apparatus well known.   In man
the perfect blood is carried from the heart by  the
aorta and distributed  to  every part of the  body.
The large arteries maybe called the distributing ves- 
PHYSIOLOGY.
17
sels.  Probably the blood  is carried  through the
arteries  principally  by  the power of the heart.
These arteries terminate in the capillary vessels,
which constitute  a  net-work.  This  net-work  is
found in  every part of the body, and it seems des-
tined to  contain, as in a store, the materials for the
use of the various parts.  From this store the ex-
treme arterial vessels derive  materials, whether
for formation, or excretion.   What  intermediate
apparatus there  is between  the  capillaries con-
taining red blood and the extreme  vessels, we do
not certainly know.   We have however reason to
believe that  by a power of  selecting the materials
wanted,  or by a power of refusing those not want-
ed, and  not  by any mechanical  arrangement, the
extreme  vessels  of every part receive  only such
portions of the blood, as are  fitted for their pur-
poses respectively.
   XXII. In regard to the capillary vessels, we have
reason to believe  that  they must always be sup-
plied with florid, or  arterial blood;  that,  if they
are not so supplied in any part, vitality soon ceases
in that part ; and that  this happens so soon, as  to
exclude  altogether the idea that the  failure of vi-
tality is  owing to the failure of nutrition.
   XXIII. We have also reason to believe that the
motion of the blood in the capillaries  is not entire-
ly regulated  by  the  motion of blood in the arte-
rial trunks;  and  particularly  that  the  degree  of
the fullness   or  enlargement  of  the  capillaries is
          3 
18
TEXT BOOK.
  referrible to their own actions, and not at all  to
  that of the  heart or arteries.
    XXIV. The blood is never stagnant in the capil-
  lary net-work, but is  constantly passing from that
  into the veins.   By  these it is  conveyed to the
  right auricle,  and  by this to the right ventricle  of
  the heart.   Such  is the  general course,  but we
  find an exception to it  in the vessels of the abdo-
  men.   The  veins  of  the abdominal viscera,  with
  the exception of the  liver,  carry their blood  to
 that organ  through  the vena portm.  This vessel
 appears to assume the office of an artery ; and, by a
 new distribution  of its blood, it fills those capillary
 vessels of the liver, which furnish the materials for
 the secretion of bile.   The blood, which is not used
 for this purpose, is again collected  into veins and
 unites with the common mass  carried to the right
 side of the heart.
   XXV.  The  blood, which is  brought to the right
 side of the heart, and as it is found in all  the veins
 of the aortal system, differs in some  respects from
 that which is sent  from the left side through the
 aorta.   The  most  striking difference,  though  it
 may not be the most important,  is  in the  colour.
 The blood of the right  cavities  of the heart, ve-
 nous blood,  is of a colour which has been called
 modena red ; that of the left  side, arterial blood,
is of a bright scarlet.   Another difference, ascer-
tained  by experiment and  already referred to, is
that the distention of the capillaries with the blood 
PHYSIOLOGY.
19
of a modena red colour will not maintain the vita-
lity of the parts, to which such capillaries belong.
Other differences have been pointed out, but there
are none ascertained to which much importance
can  be  attached, either as a means of distinguish-
ing the two kinds of blood,  or as accounting for
their difference.  It  seems certain that whatever
change  is wrought  in converting the arterial into
venous  blood, must be  wrought  in  the capillary
vessels  by those vessels, and  by the extreme ves-
sels connected with them.
   XXVI. From the right ventricle  of  the heart
the blood is sent through the pulmonary artery to
the lungs.   Here it passes through arteries,  capil-
laries and veins, as  in the aortal system,  and is de-
livered  by the pulmonary veins to the left auricle.
From the left auricle it passes into the left ventri-
cle,  and thence commences apew the  course al-
ready described.   In  passing  through  the  lungs
the blood changes  its colour and other properties,
and  this change appears to be wrought  in the ca-
pillaries.  Hence the arterial  blood of the lungs
corresponds in its characters with the venous blood
of the other parts of the body, and vice  versa.
   XXVII. The nature  of  the  changes wrought in
the blood,  while passing  through  the  pulmonary
vessels,  and  the mode in which these changes are
effected, have been the  subjects of much investiga-
tion.  The investigation has not perhaps afforded
entire satisfaction to any one.   What is certain is 
20
TEXT BOOK.
  that  the mucous  membrane  of  the lungs is con-
  stantly exposed to atmospheric air; that  this  air,
  or at least air containing oxygen gas, is essential to
  produce  the pulmonic change in the blood ;  that the
  air expired from the lungs contains less of oxygen
  gas than that inspired;  and that carbonic acid  gas
  appears  in the  air expired to have taken the place
  of the oxygen gas which is lost.   It is then obvious
  that carbon is  added to the  air inspired.  With
  this there is also discharged  from the lungs some
  vapour, which  is mostly, or entirely aqueous.   So
 far the  lungs  are shown to be excretory organs.
 Whether any thing else is effected by  the  passage
 of the blood  through  the lungs and by the influ-
 ence of the air, to  which it  is there exposed, is not
 known.   How the abstraction of  carbon, and  the
 loss of water should change the  colour  of the
 blood  and render it fit for the purposes of arterial
 blood  is not known.  But neither is it known that
 those  excretions are  not  sufficient to  effect the
 changes just mentioned.  As the capacity for heat
 of carbonic acid gas  is  less than  that of oxygen
 gas, it is probable that some heat is derived to the
 lungs in a latent state from the air.
   XXVIII. The functions  of assimilation, forma-
 tion and excretion have been  considered so far  as
 they are essential to the preservation of individual
 organized beings already in existence.   But such
beings  have the power of reproducing  their kind.
As preparatory to the consideration of this  power 
PHYSIOLOGY.
21
and the exercise of  it, it  may be well to remark,
what  otherwise deserves  especial notice, viz. that
the organs, performing the several functions  above
mentioned, those of assimilation, &c. do not act ex-
cept  upon the application of the appropriate sti-
muli,  and that certain conditions are necessary in
different cases, to their action even  upon such ap-
plication.
   XXIX. The due conditions, which vary in diffe-
rent organized beings, being complied with,  indivi-
duals of every species  are capable of reproducing
their kind.   In so doing they exercise the forma-
tive functions.   As a plant can form its  branches
and its leaves in the course of its development, so
also can it form its flowers and its fruit.  But this
fruit  contains the offspring of the plant in embryo;
and this is capable, under proper circumstances, of
being developed by its own powers and becoming
a perfect plant,  like that from  which it was  pro-
duced.   In  forming its fruit, the plant exercises no
 powers not exercised  in its own growth.
   XXX.  When stimulated by the presence  of the
 succus proprius of  the plant, the formative  vessels
 convert this, or parts of it,  into solid organs and
 secreted  fluids for the growth and  support  of the
 plant itself.   In like manner do  the formative ves-
 sels form the flower bud and all the parts of fruc-
 tification.  The several  parts of fructification pre-
 pare by  similar vessels the appropriate materials.
 The presence of these materials, or of other  causes, 
22
TEXT BOOK.
 stimulates  the proper organs to the actions neces-
 sary for effecting the ultimate purpose of their for-
 mation.
   XXXI.  In the more perfect animals the prepa-
 ration of the organs of generation, and in the male
 the presence of  the seminal fluid occasion peculiar
 sensations,  desires and  voluntary  actions,  which
 correspond with other sensations, &c. in the animal
 system  hereafter to be  considered.   What now
 deserves notice, is, that there is a general analogy
 in the functions of reproduction in  all  living orga-
 nized  beings; that these functions, so far as they
 are common to such  beings, are  similar in their
 general character to those of growth and  preser-
 vation,  as  performed  by  the  formative vessels;
 and that the arcana are not more perfectly hidden
 in the  one case  than  in  the other.  In both we
 may trace effects  more or  less minutely, but we
 cannot elucidate their production by any mechani-
 cal or chemical principles.
   XXXII.  It may be well  now to consider what
 peculiar powers or properties are  brought into ex-
 ercise in the functions which have been  described,
 as common  to all  living organized beings.   What-
 ever  powers or properties are found to exist  in
 such beings, which do not  exist  in common or dead
 matter,  may be called  vital powers or properties.
The terra vital is here  employed  as descriptive
and not  as explanatory.
  XXXIII.  First, common or dead  matter is intro- 
PHYSIOLOGY.
23
duced  into a living body,  without possessing any
vital properties, or not  the same which it is after-
wards  endowed with.   When this common  matter
is made to constitute a  part of the solids  or liquids
of the living body, it  acquires  life  and whatever
properties are  appropriate to such solids or  liquids.
But this life  and these  properties it must receive
from the living body itself.   This inference is not
drawn from  any fancied knowledge of the nature
of vitality or life ; it is drawn from the considera-
tion that there is nothing else, to which the  vivified
matter has been exposed, except the living body.
It is by that  body then, that the matter must have
been vivified.  This then  shows that a living body
possesses one peculiar power, which may be called
the power of vivification.
   XXXIV.  Second, from the consideration stated
in § X., it appears that all parts of living bodies,
all their elements, must become possessed of pecu-
liar affinities, which, in contradistinction to chemi-
cal affinity,  may receive the general name  of vital
affinities.  The decomposition of organized bodies
after death, is to be  referred  to the influence of
chemical  affinity,  which operates  among  the ele-
 ments recently united  by  the laws  of vital affinity.
    XXXV.  Third, the  various functions which
 have  been  described,  are not performed  without
 motion.  In plants this motion is principally shown
 in  the action of the vessels on their  contained fluids.
 This  motion  cannot be attributed to any of  the 
24
TEXT BOOK.
 attractions or causes of  motion which  act in com-
 mon matter, such as the attractions of  gravitation,
 electricity, magnetism, chemical  affinity,  and crys-
 tallization.  It must  be  attributed to some power
 of  originating  motion which  is  peculiar to living
 beings, and  may be called vital mobility.
   XXXVI. Fourth,  this mobility does riot  seem
 to operate spontaneously, but  only on the applica-
 tion of a stimulus either to the part,  which is to
 perform the motion, or  to some other  part con-
 nected with that.   But the  power of being im-
 pressed  by a  stimulus  is different from, though
 most closely connected  with  mobility;  and there-
 fore the  former power should have a  distinct de-
 signation.  That  power  is called  irritability  by
 those who make the distinction; for some physi-
 ologists employ this name for the two powers con-
jointly.  Irritability  is also shown  in some organs
 in the performance  of  functions,  which may  or
 may not  depend on motion, but which certainly do
 not depend on  sensible  motion.   Thus  an  agent
 being  applied  to a secretory  organ, or  to  parts
 connected with it, and its secretion being increased,
 we call that agent a stimulus,  and consider the or-
gan as  evincing irritability.   Yet it may be, that
 the action of this organ is not attended  by any mo-
 tion.   It  is  in  this  broad sense,  that  Mr.  John
 Hunter often employs the word action, without ne-
cessarily  implying  that any motion occurs.
  XXXVII. Fifth, the different parts of organized 
                   PHYSIOLOGY.                25
 beings are found to  act in connexion, so as to effect
 one object, which one part alone could  not effect.
 Instances of  this sort may not be obvious in all or-
 ganized beings.  There are however many instances
 in plants, especially in  the parts  of fructification.
 Such  cooperation has been  referred  by  some phy-
 siologists  to a peculiar  power, and this has  been
 denominated synergy.*
   XXXVIII. These properties then, viz.  vivifica-
 tion, vital affinity, mobility, irritability and synergy,
 as being common to all  organized living  beings,
 may be  called  organic vital properties.  In  like
 manner the functions, which have been  described,
 may be called organic functions.
   XXXIX.  The  functions  and  the properties,
 which have been described, are sufficient to main-
 tain simple life in any organized being.  The form,
 the  size  and  the number  of  organs  belonging
 to such  beings  may  be various.   The  apparatus
 for effecting any  one of the  functions  described,
 may be more or less complicated.   In quadrupeds
 the organs for assimilation and for the distribution
 of the assimilated fluid are vastly more complicat-
 ed  than in vegetables, and  in the lower order of
animals.   Yet in  all  there  is, probably, a great
similarity  in the  absorbing and formative vessels.
These  last most especially are common to every
* See Barthez sur le science de l'homrae,
       4 
26
TEXT BOOK.
 part, and  may be regarded as organs of  the very
 first importance.*
   XL.  It  may now  be remarked that by the func-
 tions, which have been described, other organs may
 also be formed besides those destined to the organic
 functions themselves.   Such organs  may  resemble
 those of all organized beings, so far as regards sim-
 ple life; that is,  they may  be  formed by vessels of
 the same character,  and as their particles decay
 they may be removed and replaced in the same
 manner, as  those destined for the organic  functions
 alone.   At  the same time  the superadded organs
 may possess peculiar powers,  by which they may
 enjoy a higher species of life than that of the be-
 ings, which perform the organic functions alone.
   XLI.  What is stated in the preceding paragraph
 as possible, corresponds precisely with  what actu-
 ally exists in animals of the higher order.   In man
 the superadded organs are  the brain and nerves,
 organs of sense, of locomotion and voice.   It now
becomes necessary  to describe the  functions  of
these organs very  briefly.  These   organs  have
been denominated the organs of animal life,  since
they are found  only in animals.  They  are  not,

  * If the inquiry be made how these organs  themselves are
formed, a satisfactory answer may not be furnished.  Perhaps
the speculations and experiments, in which Sir Everard Home
and Mr. Bauer have of late  been engaged,  will  lead to a
more perfect answer to this inquiry,  than can at present be
given. 
PHYSIOLOGY.
27
however,  all of them, found  in every species of
animal.
  XLII.  Without engaging in discussions respect-
ing  the nature of the mind, we may be permitted
to regard the brain as  its seat,  or as the organ
through which it operates.  In a general  view of
the  subject, it may be said that  the integrity of
the brain  is necessary  to  the  healthy exercise of
the  intellectual  and all the mental  functions, as
well as to that of the other functions of the animal
organs.
  XLIII.  The brain,  or encephalon is of itself a
very complicated organ, but the distinct functions
and  purposes of its  several parts are  unknown*
It communicates either directly,  or through  its
continuation, the medulla spinalis, with every part
of the body by means of nerves.  The nerves ter-
minate for the most part in extremities too fine to
be demonstrated by the anatomist.   It is in  these
extremities that the most  important offices of the
nerves are  performed.  The  intermediate trunks
appear to serve only as  internuncii between  those
extremities and the brain.

  *  Different functions have indeed  been assigned  fancifully
to different parts of the brain, both  in former and in  later
times; and recently some experiments have been made, from
which inferences in respect to the distinct uses of the various
parts of the brain have been drawn.  (See Edin.  Med. and
Surg. Jour, for Jan. 1824.)  But the subject has not yet been so
investigated, as to authorize us to say we have any knowledge
in respect to it. 
28
TEXT BOOK.
    XLIV.  The functions, which the  nerves are
 known to perform, are of two kinds ;  but there are
 functions of a third kind also,  which may be attri-
 buted to them with a great degree of  probability.
 These functions are,  first, those of sensation; se-
 cond, that  of producing  voluntary  motion;  and
 third, those of sympathy.
   XLV. It  is not necessary here to  describe the
 several  organs oi sensation and the different offices
 they perform.   It may  be stated generally that
 an organ of sense consists  of such  parts, as will
 favour  the  action of the object of sense  on its
 nerve.   The nerve being acted upon,  the impres-
 sion is conveyed with the  greatest rapidity  along
 the trunk of the nerve to the brain.   This  trunk
 is incapable,  in  any of its parts, of being  acted
 upon by the object of sense,  although it  can con-
 vey the  impression derived from it.   This is true
 at least so far  as  regards  any  specific  sensation ;
 for the feeling of pain may be  derived  from the
 action of a foreign body on the trunk of  a nerve.
 It is then in the extremity of a  nerve in an organ
 of sense  and in the extremity  in the brain that its
 most important powers appear to be placed.  Sen-
 sation may be  said to  take place in  the organ of
 sense ;  while perception takes place in the  mind, in
 consequence of the effect propagated to the cere-
 bral extremity  of the nerve.
  XLVI. In the production  of voluntary motion
the nerves serve  only  to convey the commands of 
                    PHYSIOLOGY.               29
  the mind from the brain to the muscles; these last
  are  the  immediate  organs  of  motion.   In  thus
  conveying the commands  of  the mind,  as well as
  in the function of sensation, the extremities of the
  nerves are the most important agents. The extre-
  mity in the brain may be considered as acted upon
  by the  mind,  and  the other extremity as acting
  upon  the muscle. The muscle may  be regarded as
  having a  power of motion similar  to that of the
  organs  of motion in all organized  beings.  The
 only peculiarity of an animal,  or  voluntary muscle
 is that it is susceptible of the stimulus of volition.
 The  phenomena are volition  in the mind  to  per-
 form a certain motion, and  the performance of the
 motion.   But  the volition  is not  followed  by the
 motion, if the  nerve be  compressed,  or cut off in
 any part of its course, or if the muscle be not in
 a sound state.   The trunk or body of the nerve
 serves only to  make  the communication  from one
 extremity to the other.
   XLVII. It appears by the  observations  of Mr.
 Charles Bell*  that  there are  distinct nerves for
 the different  functions of parts performing more
 than one  office; and  that  the nerves  of  motion
supplying different parts are in some way connect-
ed, so far as they are destined to excite motions
in reference to  the same objects.  Thus  by  the

  * See  Phil.  Trans, of the Roy. Soc. of Lond. for the year
1821. 
30
TEXT BOOK.
 arrangement of certain nerves all the  muscles, in
 any way subservient to respiration, are classed to-
 gether.   Those  nerves are called by Mr. B. the
 respiratory nerves.   The very same parts, to which
 these nerves go, are furnished with other nerves
 for the purposes of sensation and  for common vo-
 luntary motion ; for which purposes the respirato-
 ry nerves   are  inefficient.    These   respiratory
 nerves may  be regarded as sympathetic.   That is,
 they serve to keep up  a  communication between
 organs, which are distinct, but which are  often to
 act in unison in consequence of impressions made
 in one point.  By a division of any one branch of
 these nerves the muscles  supplied by that branch
 will  be prevented from acting  in unison with the
 other muscles of the same class.
   XLVIII. In the case  last supposed, in which one
 branch of  the respiratory nerves is divided, the
 muscles supplied by that branch do not lose in any
 measure their mobility.   Accordingly  they  may
 be excited to motion  for other purposes, through
 a distinct set  of nerves.   This is shown very clear-
 ly, when the  portio dura of the  seventh  pair  of
 nerves is  divided.   Hence  it  is evident, among
 other things,  that the power of motion in  muscles
 is not derived from the nerves.
  XLIX.  It  seems certain that the  functions  of
assimilation and formation  cannot  be  performed
by powers  derived  from the nerves;  since these
functions are  performed in vegetables, which are 
PHYSIOLOGY.
31
destitute of nerves*  Yet these  functions are un-
doubtedly influenced by the  nerves, and some phy-
siologists  of the  present  day have  attempted to
show by experiments on brute animals, that diges-
tion and secretion are  performed by some imme-
diate influence of the nerves.  The true explana-
tion of  those  experiments  may however be found
in considering  the nerves  as  organs of sympathy
between the different parts of the organic system.
   L. In tracing living beings from those, who are
the  most simple, to those,  who are  more  com-
plicated in their organization, we  can perceive the
advantage, if not the necessity of a  sympathetic
connexion between the different parts,  performing
the  organic functions, in those who are more com-
plicated.  In  the  vegetable there is an immediate
continuation  of vessels  from the roots to the va-
rious branches, to the  leaves and to the parts of
fructification.   But if a  part of the root is  injured,
the rest of it may continue to perform its functions
as before.   One branch  may be lopped off and the
others will not have their vigour impaired. There
is not any central organ, or  organs, whose  func-
tions are essential to the rest.   Each  part above
the ground is  dependent on some part of the  root;

  * It has indeed been suspected that vegetable beings have
nerves; but this suspicion has  arisen  only  from  a theory,
which requires them, and is not supported by any anatomical
observations. 
32
TEXT BOOK.
 but the integrity of the whole root is not essen-
 tial to any one part.
   LI. On the  contrary in the  more  perfect ani-
 mals there are  several  organs,  the integrity  of
 which is  more  or less  essential to the life  and
 health  of the  whole  bodv.  Thus the stomach
 and the other  organs subservient  to digestion la-
 bour for  the  whole body and  are  essential to it.
 So too the heart is essential, though it does nothing
 probably  in the  work of assimilation, and  though
 it possesses nothing more  of  vitality  than other
 organs and is  not  a source of vital  power to the
 other organs.   It is however essential to the whole,
 because without its aid the  constant want of fresh
 blood in every part  cannot be  satisfied.  In like
 manner are the lungs essential.
   LI I.   But  not  only  are the  different  organs
 essential to each  other, it  seems  necessary that
 they should have some correspondence ; that they
 may have, if the expression can  be allowed, a feel-
 ing of each other's  wants.   The stomach, even if
 its vitality could be maintained, would  not labour,
 if it were insulated and were  not acted upon  by
 the parts, which require the supplies prepared  by
it.   It  must feel  the  stimulus  of  necessity;  to
adopt an  expression of  Mr. Hunter's,   which has
been  unjustly  criticised.   This  feeling is  indeed
without any distinct perception  by the mind; and
if it is said that  the term feeling is not  properly
used in such a  case, then let some  other term  be 
PHYSIOLOGY.
33
employed.  The opinion intended to be expressed,
and  which is rendered  intelligible  probably  to
every one by the language employed, is not to  be
confuted  by showing  that  a word has  been em-
ployed in too limited a sense.
   LI 11.  If this doctrine be admitted, it  will pro-
bably be  allowed that the intercourse, or sympathy
between the different organs is more likely  to  be
maintained through  the nervous system  than  in
any other mode.   But this likelihood may be test-
ed by cutting off  the nervous communication be-
tween any one of the great organic viscera and
the rest  of the body.  Now this is what  has been
done by  various experimental physiologists and it
appears  that, when thus insulated, the great orga-
nic viscera fail at once to perform their functions.
The  muscles of  inspiration  will  not act, if they
have not  a nervous  communication with the lungs,
for which they act.   The stomach will not digest
food, and the  liver will not secrete bile, if  they  be
not connected by the nerves with the other  parts
of the body.
   LIV.  On the other hand it  is not essential  to
the extreme vessels, which perform nutrition, that
they should be connected  with  other parts.   If
the organs, to which they belong, are  duly  exer-
cised, these vessels  will  perform their functions.
Thus a paralytic limb fails  to be nourished, only
in proportion as it  ceases  to be  exercised.  This
is shown  by the fact,  frequently observed, that a
            5 
34
TEXT BOOK.
disuse of  a limb from any  cause diminishes the
nutrition of it; as much when it is not palsied, as
when it is.  In neither case  does the nutrition fail
entirely.   But  if every part except  the  stomach
were truly palsied,  then would the stomach cease
to act; for it would be in the  same state, as when
the nerves, which go to it, are divided.
   LV. The  sympathetic influence of the  various
organs on each other is not commonly noticed in
health, because  its only effects  are to  maintain
every part  in the  easy and regular  performance
of its functions.   But  under disease  this influence
is constantly manifested and recognized ; and the
only difficulty in  many cases is to trace  to  their
origin  the  complicated  effects  produced by it.
Thus a disease, not violent in its character and not
attended by pain, may be going on in some part of
the body  comparatively  unimportant.   This  may
occasion  a derangement in  the  functions of the
stomach; this  derangement  may soon  cause  an
irregularity  in the hepatic functions; and the dis-
order in the stomach or liver, or in both may  occa-
sion affections of  the  head,  or of the heart,  or of
the muscular system; and  thus may be produced
a series of complicated  symptoms, under  which it
may be exceedingly difficult  to detect the original
seat of mischief.   It is only  when a  knowledge of
the remote cause shows what  part was first affect-
ed, or where the disease  is situated  in some part
which is  exposed tt>  view,  or when some other 
PHYSIOLOGY.
35
 peculiar circumstances demonstrate the first seat
 of disease, that we can  certainly trace to their
 source such a series of symptoms, as has been de-
 scribed above.
   LVI.  It is then to  be  remembered that sympa-
 thy may be constantly operating in health  and its
 effects may not be noticed, because they serve only
 to maintain order ; and  that, although  its  effects
 are  more obvious in disease,  yet they may  be
 overlooked in disease also,  when  the original af-
 fection occasioning them  is not  distinctly manifest-
 ed.  But that in all cases, where nervous influence
 is demonstrated,*  and where that influence does
 not consist in sensation, nor  in the communication
 of volition, we are authorized to regard it, as an
 influence by which a correspondence is maintained
 in the  organic functions.   This  correspondence it
 is, which is denominated sympathy.
   LVII. It is next to be  observed that by sympa-
 thy the extreme vessels,  which  perform the for-
 mative  and excretory functions,  operate  on the
 great central organs, of which the heart and the
 stomach  are the most important, much more pow-
 erfully than these  great  organs  operate on  those
 extreme  vessels.  This  is  peculiarly true  as  re-
spects the  heart;  for  the stomach does operate
by sympathy  very powerfully  on all  the   other
 organs.   If however the  instances of a sympathe-

  * As in the experiments of Dr. Philip on the stomach. 
36
TEXT BOOK.
 tic influence originating in  the stomach are yery
 frequent, it is to be remembered that this organ is
 more frequently exposed to causes of offence than
 any  other  part  of  the  body.   In a  healthy  and
 vigorous state of the system  however it will bear
 very great  derangement without a  disturbance of
 any other part;  while the same is not true of the
 organs of formation and vascular excretion.  These
 remarks seem to be true in point of fact ; and the
 final  cause  of the  laws of sympathy, which they
 point out, is sufficiently  obvious.
   LVI1I. To understand this final cause it  is to
 be considered that, when the functions of the ex-
 treme vessels are deranged, it  may be very neces-
 sary that the heart, which labours for them, should
 have its actions in some measure modified.  If we
 cannot tell how this happens, that is, if we cannot
 see how the change in the functions of the  heart
 may aid  the diseased vessels in a  given  case, yet
 we can see that some  change  may be  requisite.
 On the other hand we  do not see any advantage
 in a change, or  modification of the functions of the
 extreme  vessels  under  a disease  of the  heart.
 The heart  bears a  mechanical  relation  to those
 vessels, by which it  influences them ; but it  need
 not call for  their aid,  when it  is  diseased, and
 therefore does  not  require in  them  any peculiar
 sympathy.   The  same considerations  do not ap-
 ply with  equal force to the stomach,  as relat-
ed  to the extreme vessels;  and accordingly we 
PHYSIOLOGY.
37
find the  sympathy between  those vessels and the
stomach to be  more  nearly  mutual, than between
the same vessels and the heart.
   LIX.  The functions of the nerves, sensation, and
its transmission,  the transmitting of  volition and
sympathv, are  not to be  explained on  mechanical
principles.  At least they never  have been so ex-
plained in a satisfactory manner,  though the  at-
tempt has often  been made.   Nor are  they to be
explained on  any physical  principles, with  which
we  become  acquainted  by  the  investigation of
common dead matter.  The  properties of the nerves
are strictly  vital.  The  functions they perform,
occur only in living  beings,  only in  animals ; and
we ascertain their properties  only by ascertaining
their functions.   Seeing what  these  functions are,
we say  they have the  powers, or  properties of
performing those  functions.  Thus  we say they
possess sensibility, and  the  power of transmitting
sensations so as to produce perception in the mind,
the power of transmitting volition and the power
of producing  sympathy.    These may be called
animal vital properties ;  and under the  same name
may  be  included the properties of the  mind.
   LX. Sensibility is  of various kinds.   It is specific
in the various  organs of sense.  The sensibility of
the  optic nerve is evidently different from  that of
the  auditcry nerve.  There is also a common sen-
sibility,  by which  we become susceptible of cor-
poreal pain, or pleasure.  Even in this respect we 
38
TEXT BOOK.
  find that parts of different texture, and that differ-
  ent organs have in  some measure peculiar kinds of
  sensation,  when  in pain; whence  perhaps some
  specific modification of sensibility may be inferred.
  Whether  the  power of transmission is  just  the
  same in all nerves we do not know.
    LXI. There are not any  observations, which
  show any specific  modifications in  the powers of
  nerves transmitting volition.  The  same  may be
  said in respect to the nerves,  by which sympathy
  is maintained.   This subject however may be con-
 sidered as sub judice.  Mr. C. Bell and his  disci-
 ples are engaged in collecting  the evidence. After
 they have presented this, a decision  may be had.
 In respect  to  the  power of sympathy it  must  be
 added  that  its efforts are sometimes active and
 sometimes passive ;  that  they  may be either local
 or  general;  and that, when  local,  they  may be
 manifested in parts, which are continuous, or con-
 tiguous, or remote.    Likewise what  is  called gene-
 ral, or  constitutional sympathy is  not commonly
 shown in the whole  system strictly speaking; but
 in some  one of  the subordinate systems.   Thus
 we call the sympathy general,  if it is shown in the
 circulating system,  or in the  system of extreme
 vessels, or in the muscular system, &c.
  LXII. Perception  and volition are the functions
of mind  most distinctly connected with the func-
tions of  the nerves.  These  functions certainly
show distinct powers in the mind; powers obvious- 
PHYSIOLOGY.
39
ly different from  those of memory, judgment, &c.
This doctrine is not, and cannot fairly be regarded
as inconsistent with that of  the unity of  the mind.
Nor is it inconsistent with  the doctrine of the im-
materiality of the mind.  If these propositions be
denied, the burden of proof  must rest  on those,
who deny them.   The  powers, or properties of
the mind  are  obviously to  be included  among the
animal vital properties.
   LXIII.  The various functions of  the human
body having now been stated in general  terms, it
may be convenient to notice more  distinctly the
relations, which are maintained between the different
organs performing these functions.  These organs
are related to each  other  in two  modes, which
may be denominated mechanical and vital.  The
mechanical  relations depend on causes similar to
those by which the different parts of an inanimate
machine may be connected with each other.  The
vital relations are such as belong only to living bo-
dies, depending on  the vital  properties.  These
two kinds  of relation may be illustrated  by a few
instances.
   LXIV. When  the stomach  propels its contents
into the duodenum, its influence upon that intestine
is similar to that  of one part of a machine deliver-
ing its contents to another part of the same, in or-
der  to produce some  action  in  that.   Similar to
this is  the influence of the heart upon the arteries,
when the former  pours out its blood into the latter. 
40
TEXT BOOK.
Such too is  the influence  which  the diaphragm
exercises  in  its motions  upon  the viscera of the
two cavities, which  it divides.  That is to say, in  •
each of these cases  the  relation of the one organ
to the  other is  mechanical,  although the moving
organ acts by a  vital power.
   LXV.  When a nerve,  being acted upon by a
foreign body, propagates  the  effects to the brain,
the influence is such as  is  exercised only in  living
bodies.   There is not any evidence  that in  this
case matter,  or even  motion is propagated along
the nerve.  The same  is  true in respect to the
propagation of volition;  so that the relation of the
brain to the voluntary muscles  may be called vital.
The same is  true in  respect to organs,  which ex-
ercise a sympathetic influence upon each other.
   LXVI. There  remains to  be  noticed certain
effects  resulting from  the  relation of  the  body to
the mind.  The mind  is affected  by the body not
only from causes  operating on, or in the  body,
which  occasion distinct sensations.   The mind has
also the emotions of pleasure or pain from  states
of the  body,  of which states, however,  it does not
take any  distinct cognizance.  There is a feeling
of vigour, of  satisfaction, of comfort, or of  hilarity,
which  arises from  the  full  possession of all  the
powers, and  the easy performance of all the func-
tions of the boHy.  Opposite feelings  result from
an embarrassment of the functions, or a failure in
the powers,  which do not necessarily acquaint the 
PHYSIOLOGY.
41
mind  with the  difficulty  which  exists,  nor even
with the situation of the difficulty.   Certain states
occasion  those  desires called appetites, in which
the mind is influenced by  the changes in the body,
as positively as in common sensations ; but  without
any definite perceptions  of  those changes  in the
body.  We discover by observation that the appe-
tite for meat  and drink  arises in us when empty,
or after  fasting,  while the desire for Venus arises
in us when in a certain sense full; and  that both
are much  influenced by  the presence,  or  by the
thoughts of its object.  But the  sensations accom-
panying,  or exciting the desire or appetite  in these
cases, are neither definite nor exactly local.
   LXVII. On the other hand, the mind acts upon
the body in  modes, which   may be called sympa-
thetic.   Certain thoughts  being  present   to the
mind,  the  heart beats with more frequency and
greater  force ;  the respiration becomes deep and
hurried ;  there  is  an uneasiness  in  the  muscles,
which prevents rest,  or  which  seems to  demand
violent efforts; the  countenance is distorted and
becomes alternately pale and red,  while  the eye
fixed on  one object seems  not to be  acted on by
common things.  Some of these effects are entirely
involuntary,  and all of  them  in  a measure so.
They  denote the passion  of anger, which   has its
seat certainly  in the mind,  though its  effects are
manifested by affections of  the body.    Analogous
manifestations of the other  passions  are also well
           6 
42
TEXT BOOK.
 known.   In all  these  cases  the affection of  the
 body may be  said to  result  from  sympathy with
 the mind; and there is discovered  a vital  relation
 between the mind and body.
   LXVIII. It may next be  considered  what  are
 the physiological relations maintained between  the
 living  body and  external things.  These relations
 must depend on  the properties of the body, which
 enable it  to  act upon external things, or  to be
 acted  upon  by  them, and  on  those  of external
 things capable of acting on it.   The properties of
 the living  body,  which enable it  to  act or  to be
 acted upon, are of two descriptions, physical and
 vital;  the physical properties being such as it has
 in common with other  matter; the vital properties
 such as have been already described.
   LXIX. The living body is subject to gravitation
 in common with  other  matter.   It  is  also subject
 to the action of mechanical  powers.  Bv the  influ-
 ence of  these  its structure  may  be injured.  The
 injury, or imperfection  thus  produced, is followed
 by actions in  the  parts injured, the  tendency of
 which is to restore those parts  to a sound state.
 The living body  may be acted upon, in any of  its
 parts, by substances having  a strong chemical affi-
 nity for  those  parts.   In this case vitality is de-
 stroyed before, or as soon as the  chemical affinities
 operate.   If agents capable of so acting have their
strength  diminished below  a certain  point, their
effect is  to produce a sudden inflammation.  Thi* 
PHYSIOLOGY.
43
is seen in the influence of heat.  When a chemical
action does  take place,  the part acted upon  be-
comes a foreign body, and there ensues the process
of restoration, as where a  mechanical injury has
been inflicted, and the dead matter is at the same
time  thrown off.  The living  body, by its power
of motion, may act mechanically on external things.
There may also  be some other physical relations
between the living body and external  things.
   LXX.  The vital  properties, which enable  the
living body to be acted upon  by external  things,
are two.   These are irritability and sensibility.   A
foreign substance applied  to, or introduced into the
body, will induce  either sensation or action, or both,
in the part to which  it is  applied.  A local effect
having thus been produced, further effects may en-
sue in consequence of  the  relations between diffe-
rent  parts of the body.  Thus, in consequence of
the mechanical  relations, such  substance  may  be
removed from the part to which it is first applied,
and may  be  made to  act  successively on various
parts of  the body.  Or, either sensation or action
mav be induced  in various parts  of the body  in
consequence  of the vital relation of sympathy ex-
isting between such  parts and the part first affect-
ed.   But  in  every case the foreign substance acts
primarily and directly upon either the  irritability
or sensibility.
   LXXI.  The particular effects of substances act-
ing on the vital properties will depend on the cha-
racter of those substances.  It is only by experi- 
44
TEXT BOOK.
ment on the living  body, that this  character can
be ascertained.  We do not learn it  by ascertain-
ing the  physical, or chemical properties of the fo-
reign substance.   This  is shown  most distinctly in
the influence of substances used as medicines.   But
it is shown in other cases.  For instance, our know-
ledge of the chemical  properties of acids would ne-
ver lead us to a knowledge of their taste.
  LXXII.  The following may be taken as an ex-
ception  to the remarks in § lxx—Ixxi.  Besides induc-
ing sensation and action, it is probable that foreign
substances  may in some  instances operate directly
to diminish or suspend a vital power.  It is not
easy to  explain the effects of  narcotic substances
upon  any other  principle.   Such substances have
been called stimuli; and  this upon the ground that
they first excite action before they  produce seda-
tive  effects.   It does  not appear, however,  that
they do, all of them, excite action; nor in any case
does there  appear such a proportion  between their
stimulant and  sedative effects, as that the latter
can be regarded as consequences  of the former.
  LXXII1.  The conditions necessary to the main-
tenance  of  life may next be considered, and  thus
its termination or death will  be brought  readily
into view.   In order  to determine what are the
conditions necessary to the maintenance of life, it
is proper to fix with some precision  what we mean
by life and living beings, referring of course to such
living beings  as we discover  on our  globe.   It 
PHYSIOLOGY.
45
might have seemed proper to have given an earlier
attention to this point;  but it was believed that it
could be done with the greatest advantage after
the statements which have preceded.
   LXXIV. Living beings  are those which are ca-
pable of growing by intussusception, and for  this
purpose of assimilating foreign matter  to them-
selves; and  which, when  perfect  of  their kind,
are  capable  of  perpetuating their species.  By
this definition, we may  at  least distinguish living
beings from common matter in  all  ordinary cases.
Such beings possess certain properties, which have
been described,  and which they are capable of
communicating to the materials they assimilate to
 themselves,  and of transmitting to their offspring.
 The possession  of  any  one of  these properties by
 any substance, if at the same time it be  capable of
 being excited to its proper functions, is an evidence
 of life  in that substance.   Thus a seed,  or an egg,
 are possessed of life; but  a piece of wood, though
 its elements  continue to be united by vital affinity,
 is not possessed of life.   The same may be said  of
 the  flesh of an animal preserved by  art.   The
 wood  and the  flesh do indeed exhibit  one of the
 properties of life, but they are not capable of be-
 ing  excited  to perform  any of the  functions  of
 life, which  the egg  and  the seed are  capable of.
 The vital property  they exhibit  is vital affinity.
 It  is at least so far manifested as this; that the
 particles of  the wood and flesh continue  to  be 
46
TEXT BOOK.
 united  apparently in the same manner  as during
 life.
    LXXV. The conditions,  necessary to the main-
 tenance of life, are not the same in cases where
 there is simple vitality with a capacity of perform-
 ing the functions of  life as  in the egg, and where
 those functions  have once  commenced  as  in  the
 animal.   To the egg and  the seed it is  necessary
 that their texture should be uninjured;  and in all
 instances,  perhaps,  there are  certain degrees of
 temperature  necessary to  them.   Thus  an  egg
 will be frozen  in a certain temperature,  and then
 vitality is  lost.   This  temperature  is  below that
 at which water freezes.   An egg is also coagulated
 at  a certain elevation  of temperature,  and then
 also vitality ceases.   Seeds may likewise  lose their
 vitality by a  certain elevation of  temperature;
 and probably  there  is a  point, below which  no
 seed can retain life.   But the range of temperature
 consistent  with  life  is very considerable in both
 these cases.
  LXXV1. In  regard  to both vegetable and ani-
 mal beings in the more perfect state, that is, when
 performing the functions of life, a  temperature of
 a more limited  range is requisite to vitality.  Be-
 low  a certain  temperature  some  become torpid,
 and  they are revived  when placed  in a proper me-
dium of  a  higher temperature.  Others,  animals
at  least, are incapable of passing to the  torpid
state, in which  most of the functions are arrested; 
PHYSIOLOGY.
47
and  they cannot  live at all, except within certain
limits, as to temperature.   In  the more  perfect
animals,  there  is a power of maintaining a certain
fixed temperature  under great  variations of  the
surrounding medium; but this power has its limits.
Those limits vary according to the habits of indi-
viduals.  This is true,  in respect to man, most es-
pecially.   Thus man can live, where mercury free-
zes,  provided  he guard his body by such clothing
as is a sufficiently slow  conductor of heat; so  that
the warmth generated  in his own body may not be
too rapidly dissipated.   Likewise man can live in
a temperature of the atmosphere much above that,
at  which dead animal  substances  are coagulated.
But life could  not,  probably,  be maintained for a
long time in so high a  temperature.   Probably all
livino- beings possess, in some measure, the power
of regulating their own temperature; although it
 is  in the warm blooded animals that this power
 exists in the most eminent degree.
    LXXVII. A supply  of  atmospheric air, or of
 some air containing oxygen, is also requisite  to the
 maintenance of the functions of life,  at least in all
 warm-blooded animals.   Without  this the venous,
 or  black  blood,  is  not  changed  to  the  arterial.
 (See § xxv.)   A  third requisite is the  supply of
 food. Although this supply may be wanting, with-
 out  the loss of life, for a time  much  longer  than
 that for which  atmospheric air can  be dispensed
 with ; yet, beyond a certain time, life cannot be
 maintained without food. 
48
TEXT BOOK.
   LXXVIII. Of the articles of food water is that,
 of which the most constant supply seems necessary.
 Indeed,  as this  does not  undergo changes in the
 living body so much as other articles,  it may be
 doubted whether  it should be called an article of
 food.  The  presence  of water  appears to be as
 essential  to certain microscopic animals, as that of
 air to man, &c.; and life  may apparently be sus-
 pended and  revived by the alternate removal and
 supply of this fluid.  (See  Spallanzani on resurrec-
 tion of animals.)  But to all living organized bodies
 water seems to  be essential; though some can im-
 bibe it in sufficient quantities from the atmosphere,
 while others can live only  where it is furnished in
 most abundant quantity.
   LXXIX. The necessity of substantial food is
 less urgent, for a limited time, than that of water.
 Yet  beyond a certain time life cannot be preserved
 without other food than that  article.  The quan-
 tity of such  food absolutely  requisite for life is
 much less than that ordinarily taken.  Habit has a
great  influence in  this  respect.  By degrees man
may become  able to support life on an exceedingly
small quantity of food.   The  exercise taken has a
great influence also as  to the quantity of food re-
quired.
   LXXX. The  conditions mentioned (§ lxxiii—
lxxix) relate to external things.  It is lastly necessary
to the maintenance of life  in man, &c. that the or-
ganization of the great  central organs be entire, or 
PHYSIOLOGY
49
nearly so; and that the vital powers or properties
exist in due degree.
   LXXXI. From what has been stated, it may be
learnt how death takes place.   In the first place, if
the circulation of the blood  be suspended,  all the
organs die.   This happens because the blood does
not distend  the  capillary system.   In the second
place,  if the respiration fails, death ensues.   This
happens because the blood, sent from the heart
through the aorta, has  not undergone the  proper
changes.   In the third place, an injury of the brain
may cause immediate death.   It has  been shewn
by M. Le Gallois, that the whole cerebrum and the
whole cerebellum  may be removed, and yet life is
not immediately destroyed, while the medulla ob-
longata remains entire.   But the injury of the me-
dulla oblongata,  or a  division of the medulla spina-
lis at its upper part,  instantly destroys life.   It has
been clearly proved  by experiment,  that such  in-
jury destroys life by  stopping respiration.  This it
does  by destroying  the communication between
the par vagum and the intercostal nerves.
   LXXXII.  When life is destroyed in either of the
three modes mentioned, (§ lxxxi.) the patient may
be said to expire at once; but  absolute death does
not take place instantly in every part. The muscles
contract after expiration, and the vital properties
are lost more or less gradually.  But in some instan-
ces absolute death  takes place instantly, and then
the muscles do not contract, but remain flaccid* and
              7 
SO                TEXT BOOK.

the vital properties are  all lost  at once;  so that
putrefaction  ensues  immediately.   When death
takes place under disease,  it happens sometimes
from a failure of the heart,  lungs, or brain, in the
performance of their functions, in consequence of
a local affection of one of those organs.   But more
commonly  the  powers  of  life  are  slowly  ex-
hausted, so as  to cause a gradual  failure  of respi-
ration and a subsequent gradual loss of all  vitality
after expiration.  This  exhaustion of the  powers
of life may arise in consequence of long continued
local irritation, or in consequence of some cause
directly destructive of those  powers. 
PATHOLOGY.
  LXXXIII. This division of the science of medi-
cine relates to the doctrine of diseases. Disease can
be defined only by contrasting it with health. There
is much more difficulty in defining the terms health
and disease, than in the practical distinction of the
states, which they designate.
  LXXXIV. Inhealth every organ is ready to per-
form its proper functions under the appropriate cir-
cumstances, and some of the  organs are continually
engaged in the performance of their functions, others
are occasionally so engaged.   The whole body is
at ease;  the  discharges from  the body  have re-
spectively certain appropriate characters, and the
alternate states of sleep and watching can be fully
enjoyed.   What are the proper functions, &c. &c.
it is the business of physiology to  teach.
   LXXXV. Strictly, every  departure from the
state of perfect health is a disease; but slight devia-
tions from that state would not be practically regard-
ed as such.   A disease may be defined to be a state,
in which we experience pain  or suffering; or in
which there may be discovered some change from
a healthy state in the  composition, structure,  or 
 52                TEXT BOOK.
 functions of some part, or in some one of the natu-
 ral appetites.*
   LXXXVI.  In the study of diseases we have to
 attend to their phenomena, or symptoms, and their
 causes.
   LXXXVII.  We may regard each  departure
 from health, or each symptom as a distinct disease.
 But a very little attention  to  the subject suffices to
 show that a single morbid affection may give rise to
 two,  or  more symptoms.  Hence, when several
 symptoms are present, we are  ordinarily lead to
 refer them to  a single morbid affection as their im-
 mediate,  or proximate  cause.  Other notions  re-
 specting a proximate cause may at some times have
 prevailed;  but the expression is now used in the
 sense here referred to.
   LXXXVI1I. It  is  by the symptoms that a dis-
 ease must be described; because by these alone it
 can be demonstrated.  The proximate cause may be
 disputed, and must often be a matter of doubt.   It is
 not possible to dispute about that which is demon-
 strated ;  but men will never  agree in  respect to
 that which is hidden,  and which  is matter of  infe-
 rence.
   LXXXIX. In ascertaining the proximate cause of
 a  disease,  or  that which  may be regarded philo-
sophically as the disease, aid  is  derived  from  an

  * For distinguishing disease from health in practice, it is
quite essential to be familiar with the phenomena of health
On this subject see Hall on Diagnosis. 
PATHOLOGY.
53
examination of the body in the fatal cases of that
disease.  But, in considering only what happens in
the living body, this cause must be learnt  by at-
tending to the symptoms in the order of  their oc-
currence ; by noting at  what intervals they  follow
each other;  and by considering, in respect to each
symptom to what organ it is to be referred,  and of
what function it  denotes a  derangement;  and
finally, by inquiring how far one of these  derange-
ments has an influence  in producing another.   On
these points  physiology affords material aid.
  XC.  It  must  be obvious  that the expression,
proximate cause, is relative.   The symptoms  may
all be traced to one local affection ;  and this is the
proximate  cause  of those symptoms.   But   the
question may  then  arise,  on  what  particular
changes  or  actions of the part this local affection
depends.  Thus, if the symptoms be traced to an
inflammation of any part, it will be  asked in what
does inflammation consist, and what is its proximate
cause.
   XCI.  When the symptoms and their proximate
cause are ascertained,  an  inquiry must arise  how
the original affection  denominated proximate cause
has been produced.  The  causes of this original
affection are called remote causes.  Of these, there
are said to be two kinds.
  XCII. There are many circumstances, such as ex-
posure  to  vicissitudes  of weather,  great fatigue,
errors of diet, watching, &c. which are often fol- 
54
TEXT BOOK.
 lowed immediately by disease.  But of many per-
 sons exposed in  the same way at the same time,
 all are not affected with disease ; and among those
 affected different diseases are  produced.   The in-
 ference is then that some are predisposed to dis-
 ease generally, while others are not so;  and that
 some are  predisposed to particular diseases.  Hence
 it appears  that  the circumstances, such  as  are
 above mentioned, operate  only to excite disease
 in  those,  who  are   predisposed  to be diseased.
 Those circumstances, then,  are called exciting or
 occasional causes.
  XCIII.  But the predisposition to disease must also
 have  a cause.   This  is  called  the predisposing
 cause.  Both this and the exciting cause having an
 influence  in producing the proximate cause, they
 are called by way of distinction the remote causes.
   XCIV.  It does not always happen, that two re-
 mote causes act.   One is sometimes sufficient, either
 from its peculiar nature,  or character; or from  its
 acting  with  great  force, or for a  considerable
 length of  time.   In some instances one only  of the
 remote causes is known,  and yet it  is known that
 the other has existed and operated.
  XCV.  It is always  satisfactory, if possible, to as-
certain the mode in which the remote causes ope-
rate on the body, how they produce the first mor-
bid changes,  as well as in what those changes con-
sist.  Respecting their  mode of operation, how-
ever, our  knowledge  is often deficient, even when
the influence of the remote causes is  indisputable. 
PATHOLOGY.
55
  XCVI.  Our knowledge of the symptoms of a dis-
ease is obtained in different modes.  Some of them
we  learn  by our own observation and examination
of the patient;  others we learn from the account
which the patient  gives of  himself.   In general,
those which  are learnt in the first mode deserve
to be relied  on  more  than the others;  and that
from various considerations.
  XCVIl. The symptoms which arise in the various
morbid states of the human system, are numerous.
Most of these symptoms are capable of existing in
various degrees, and  are liable to some  modifica-
tions.  They may  also be variously  combined.
Hence the great variety, the almost endless variety
in the diseases, which the physician is called  to see.
  XCVI1I.   In examining a patient, whose system
presents  many marks of disease, in  order  to be
assured  that all  the symptoms are noticed, it is
convenient to adopt some method.  For this pur-
pose it may be well, first, to attend to the organic
functions in  their order, viz.; those of assimilation,
formation and excretion.  Then  to examine  re-
specting the  animal functions, viz.; those of sensa-
tion, the intellectual or mental functions, and those
of locomotion and  voice.  Lastly, to observe any
deviations from health,  as  manifested in the coun-
tenance and figure, which result from the combina-
tion of  derangements in the organic and animal
systems.   The order, in which the symptoms have
occurred; the severity of  each; their  constancy, 
56
TEXT BOOK.
  or inconstancy;  the regular,  or  irregular recur-
  rence of  any of  them; and all their mutual rela-
  tions must be ascertained  in order to a due under-
  standing of the case.
    XCIX. The proximate cause, as has already been
  stated,  is  the  primary  morbid  affection,  which
  gives rise  to all  the symptoms in a disease,  and
  which  may be  regarded  philosophically  as  the
  disease  itself.   Regarding  the  proximate cause in
  this way, it may easily be shewn that it undergoes
 changes in the  progress of what must  practically
 be called the same disease.
   C.  It may now be useful to consider, in a  ge-
 neral way, those states of  the  body which have
 been regarded as the primary morbid affections or
 proximate causes  of diseases.  In this way some
 general principles  may  be ascertained, or approxi-
 mations  may be made to some such principles, as
 will be  useful  in  the subsequent examination of
 particular  diseases.  The different medical  theo-
 ries which have prevailed,  have been founded on
 the general principles, which have been  adopted
 by their  authors on this subject.
  CI. All  the  opinions which have  been adopt-
 ed in reference to the proximate causes of diseases,
 numerous as they are, may be referred to four
 heads.  First, those which  place those causes  in
 the fluids, i. e.  in  a  redundancy or deficiency  of
some  of  the fluids,  often  connected with  some
change in their composition ;  or in some change in 
PATHOLOGY.
57
 composition alone.   Second,  those  which  place
 them in some change in the structure of some part
 of the  solid organs.   Third, those which  place
 them  in some change in  the  vital  properties.
 Fourth, those which place them in some change in
 the functions.   Of  course,  the  different  opinions
 here adverted  to have in  some  instances been
 combined.
   CI I. First, of causes in the fluids.  Under  dis-
 ease there  appears in  some cases  to be  a redun-
 dancy,  in  others  to  be  a  deficiency of blood.
 The redundancy  appears  sometimes  in  an  in-
 creased fullness of the  arteries,  sometimes in dis-
 tention  of  the cutaneous  capillaries,  sometimes
 in  an enlargement  of  the  superficial veins.   It
 appears also in an enlargement, or  in a sense of
 fullness  of  some  organ, accompanied by  circum-
 stances,  which  show  that  the  increase  of bulk
 arises  from increased  distention  of the  blood-
 vessels  of such organ.  Likewise, a spontaneous
 discharge, or an artificial evacuation of blood often
 gives such immediate relief,  as to occasion the  be-
 lief that a sanguineous  plethora,  either general or
 local, had been a cause of disease.  Circumstances,
 generally the opposite of those here  described,
 may seem  to  evince  a deficiency of  blood;   as
shrinking, deficiency  in the  secretions, paleness,
and smallness of the  arteries and  veins.
  CIII. In other cases  of disease, a redundancy of
watery fluid, or of mucus, and sometimes a defi-
              8 
58                TEXT BOOK.
ciency of  these  will  appear  in  the  discharges.
Likewise bile is sometimes poured forth in disease
in great abundance; in other cases  it is deficient*
   CIV. It has also been supposed that all the fluids
of the body are occasionally in  a morbid state;
that is, that  their composition  is  varied from  that
of health.   Thus, the  blood is thought sometimes
to be too thick, at others  too  thin; and its  diffe-
rent proximate  elements  are  suspected to vary
from the due proportions of health.   It has been
thought, too, that  the composition of this fluid may
be  varied by substances  introduced into  it,  and
sometimes by intestine changes, by which  its ele-
ments may be degenerated.
  CV. Undoubtedly there  is some foundation  for
these various  opinions  respecting morbid changes
in the blood.  But observations in respect to  that
fluid in  diseased  subjects,  comparing  it with the
blood of health, have not been made with sufficient
accuracy to determine  just how far any of these
opinions can be supported.   The  subject is attend-
ed with great difficulty.  One circumstance, which
deserves especial  attention, is  that the blood-ves-
sels may sometimes contain  other  materials  besides
the blood,  so that a cause of disease may perhaps
be in the blood-vessels, and not in the blood.   Va-
rious substances received from without, are detect-
ed in the evacuations unchanged, or nearly so; and
some of  these  have even   been  detected  in the
blood.   But the nutriment, which is changed into 
PATHOLOGY.
59
blood, has its  properties changed.  There arises
then a strong probability, that the substances which
pass through the vessels without losing their pro-
perties, never  constitute, strictly speaking,  a part
of the blood;  that is, that  they are mixed with the
lymph, albumen, &c, without combining with either
of them.
   CVI.  The blood itself is  formed from the nu-
triment by the influence or action of certain living
organs.  It is consumed by  other  living  organs in
the various processes of formation and excretion.
Any redundancy or deficiency of the blood is  then
to be attributed to a  want of due proportion m
the functions of supply and of waste.   If the blood
be not  perfect in its  composition in any  case, this
must be attributed to  some failure  in the  perform-
ance of the functions of some of the organs above
referred to.   In that case, the change in  the blood
is not a  primary affection;  the  primary affection
taking place in the functions of one or more of the
organs.  If, however, there  be  a want  of  nutri-
ment, there may  be a consequent  want  of blood,
and only excrementitious matter  may be supplied
to the vessels.  But if the difficulty be referred to
some foreign substance mixed with the blood in its
vessels,  it is  to be observed that this  substance,
should it  be a cause of disease,  must  be regarded
 as a remote cause.  The  proximate cause will be
 the change, which this foreign substance produces,
 in the powers or  functions of the living organs. 
60
TEXT BOOK.
  CVI1. Arguments of the same kind may be ad-
duced to show that all changes in the other fluids,
either in their quantity or quality,  must be refer-
red to some change in the organic functions, as the
primary affection.
  CVIII.  The importance of these views will be
obvious, if we anticipate the remark that our reme-
dies should be such as to correct the first evil, be-
fore we can look for  a  lasting cure of a disease.
It is in this mode of regarding it that a considera-
tion  of the  proximate  cause becomes  most in-
teresting.
  CIX.  Second, of causes in the structure.   Chan-
ges of  structure have not often   been regarded
as constituting the proximate causes  of  disease.
Unless  we take  into  view  injuries of structure
produced  by mechanical violence,  or by chemical
means,  changes   of  structure  must be referred
to some imperfection  in  the formative  functions.
In this  case the  change  of structure  is  secon-
dary,  not  primary.  But  there are  some cases,
in which we may be  excused, if,  practically,  we
regard  the change of structure as  the proximate
cause of disease.  Thus in organic diseases, where
the first change of structure  derives all its impor-
tance from that of the part in which it has occur-
red,  and where we may  not be able to ascertain
the nature of that first change during life, we have
to look  to the organic change as  the  proximate
cause.   But, strictly, we should look to the disease 
                    PATHOLOGY.               61
  by which  the change of structure is produced, as
  the proximate cause; and if  this first  disease can
  be ascertained,  we must inquire how far this can
  be relieved.   The organic  diseases referred to in
  this section constitute a natural tribe of great im-
  portance.
    CX.  Third,  of causes  in  the vital  properties.
 How  far a change,  a diminution,  or  an  exalta-
 tion of one or  more  of the vital properties may
 be  the primary change  produced  by the  action
 of the remote cause  of disease in  any case, is a
 question not very easily decided.  There does cer-
 tainly appear to  be reason for the opinion that the
 substances, which we  call narcotics, operate direct-
 ly  to diminish sensibility and  irritability, indepen-
 dently of any influence those substances may exer-
 cise in changing the functions.  It is not improbable,
 that in other cases the vital  properties are immedi-
 ately affected by  the remote causes of disease.  But
 in a large proportion of cases, we may regard the
 subject practically in  the same  light, whether we
 do  or do not admit this direct influence of foreign
 agents on the vital  properties.   For the effect of
 any change  in the properties will  be manifested by
 a change in the functions ; and a restoration  of the
 properties  to a  healthy state  is  to be learnt only
 by a restoration of the functions; and what reme-
dies, or mode of treatment, will effect such salutarv
change is  learnt only by experience.
  CXI. Fourth, of causes in  the functions.  In the
majority of diseases, then, we  look for the proximate 
62
TEXT BOOK.
 cause in the functions.  Under disease, the functions
 of some part are interrupted, or so excited or modi-
 fied, as to differ from those of health.  Very com-
 monly, the changes produced have the effect to re-
 move the  remote cause of disease if present, or to
 obviate and remedy  any  evil consequences it may
 have  produced.   In  consequence of the relations
 existing between the different  parts of the human
 systsm,  the disease is propagated to parts not ori-
 ginally affected.   It is in  this way often the nume-
 rous symptoms are produced in what is practically
 regarded as a single disease.
   CXI I. To form an acquaintance with  diseases
 we should observe the phenomena  they  present,
 and  trace  them to their causes.   But it  may  be
 of some use to bring into review the different func-
 tions,  and  to  consider, briefly  in  what way they
 may be diseased, stopping to notice more  particu-
 larly such diseases of them, as  we believe  actually
 to occur.  In so  doing  we  shall proceed  from
 causes to effects.  To a  certain extent,  this me-
 thod  has its advantages  in communicating know-
 ledge, though not the  proper  one for the acquisi-
 tion  of it.
  CXIII. First, then, of the functions of  assimila-
 tion.   While  the organs, which perform these
 functions, retain  their powers sufficiently,  and ma-
 terials are  furnished in due quantity and quality
 and at proper intervals, and no noxious cause ope-
 rates,  we must presume that the functions will  be
duly performed.  But a failure in these conditions 
PATHOLOGY.
63
may cause a  diseased performance of those func-
tions.
  CXIV.  The   powers,   and  consequently  the
functions,  of  the organs  of assimilation  may be
impaired  in  various modes;  as,  first,  by an ex-
cess or  defect  of  nutriment;  or by  substances
which  are not nutritious, whether mixt  with those
which  are nutritious, or  not  so; or, second, by
affections of  other  parts inducing sympathetically
a loss of power  in  those organs ; or, third, by the
mere decay of powers by age.
  CXV.  The   causes  enumerated  will  produce
various derangements  in  the  alimentary  canal.
Every organ is  fitted  to bear the stimulus of cer-
tain  substances  adapted to it,  and  the effect of
such stimulus is  to promote the easy  performance
of its proper functions.  But other substances ope-
rate as an unnatural and offensive stimulus, and de-
range the functions.  Thus, undigested food is  a
natural stimulus  to the stomach; but  it is an un-
natural stimulus  to the intestines, and is  liable to
derange their functions.  These remarks lead to
an explanation of many of the derangements  which
occur,  when, from any cause,  the stomach pro-
trudes  into  the  duodenum  any thing else  than
chyme.  The secretions of the mucous coat of the
canal will be affected, as well as the actions of the
muscular coat; and the subordinate organs will also
be affected in  their secretions.  The  undigested
mass may be expelled by  the efforts to which the
canal is excited  by  the offence of this mass.   But 
64
TEXT BOOK.
this does  not  always  happen in season to prevent
further evils.   Sometimes the stomach, sometimes
the intestines or some portion  of them appear to
become torpid,  and then the  materials  retained
undergo decomposition.  In this way flatus is  ge-
nerated, and various acrimonious matters are pro-
duced in like manner.
   CXVI.  In the next place, it may happen that
the lacteals and  bloodvessels will be offended  by
the matters  received  into  them, or  may suffer
from  the want of due supplies.   That the lacteals
may take up other articles besides perfect chyle will
scarcely be doubted at the present  time.  These
articles may not be combined with the chyle, and
may never be combined with the blood;  yet the
presence  of them  in  the lacteals,  lacteal glands
and bloodvessels  may offend  and injure those  or-
gans,  or derange  their  functions.   Likewise the
want  of chyle to form new blood  may give  occa-
sion for various affections of the bloodvessels, and,
especially, may diminish their power.   The powers
of these vessels may also be injured in other ways,
as well as those of the stomach.   The derange-
ments, however,  of the bloodvessels, considered
as organs  of  assimilation, are probably much less
frequent,  and  certainly  are less easily detected
than those of the alimentary canal.   The effect of
such a derangement of the bloodvessels  probably
must be general weakness, and  especially a failure
in the processes of formation and in those of vas- 
PATHOLOGY.
65
 cular excretion.   Possibly other effects, such as in-
 flammation in various  parts,  and perhaps dropsy
 may ensue from  the same cause.   May not scurvy
 be referred to the same cause ?
   CXVII.   There  are  certain  derangements  of
 the sanguiferous organs, considered as constitut-
 ing the circulating  system,  which  may  be  pro-
 perly  noticed in  this  place.  These consist  in
 an  unequal  or  disproportionate  distribution  of
 blood.   An  increased determination of blood  to
 a particular  part  takes place in many  cases  in
 consequence  of  an  irritation of such part.  Such
 an increased determination is an ordinary concomi-
 tant of inflammation;  but it does  not constitute
 inflammation.  In the  cases  here referred to,  it
 is  in  the  capillary  vessels  principally  that  the
 accumulation of  blood  takes  place.  The immedi-
 ate  cause  of this accumulation appears to be an
 enlargement or dilatation of those vessels.   In this
 dilatation those  vessels may  be  either  active or
 passive; but  probably they are in most cases ac-
 tive.   In  the cases referred to,  the dilatation
 sometimes extends to the arterial trunks, or larger
 vessels leading to the part, and sometimes it would
 seem that all the arteries are dilated or enlarged,
 When this  happens, the increased fulness of  the
 arteries must be  at  the expense of the veins.   In
 other cases,  this  fulness of the arterial trunks oc-
curs without an enlargement of any portion of  the
capillary vessels.   Again, there are cases in which
            9 
66               TEXT BOOK.
both the arteries and capillaries are unusually con-
tracted  for  a longer or  shorter  time; in  which
cases, the accumulation  is ordinarily in the veins.
But if the accumulation is in the veins, it may be
in some  portion  of  them  only.   Probably, indeed,
almost certainly  in some  cases,  where  the arteries
are contracted, the accumulation takes place prin-
cipally about the right side of the heart and large
venous trunks.   In other  instances, the pulmonary
vessels are distended, while the whole aortal sys-
tem has less than its proportion of blood.   In the
instances of  increased fulness in any part of the
venous system, the immediate cause is  most  proba-
bly a passive dilatation of that  system.   The un-
due accumulation  in  the  lungs, probably,  takes
place from different causes, and  may sometimes be
most in the arteries,  at  other times in the veins,
tec. as happens in the aortal system.  Now all this
irregularity  in the  distribution  of  the blood re-
quires to be much regarded  in a practical view—
since it is a circumstance on which  the importance
and danger of a  disease  may depend,  though not
the proximate cause.
  CXVIII.   Next of the  functions of formation.
These are liable to be diseased in various  ways,
and from various causes.    First,  any want of sup-
ply, or the supply of materials not  of good quality
by the blood-vessels, or the presence of any offen-
sive materials in  these vessels mixed with the blood,
may occasion some change in the actions of the for- 
PATHOLOGY.
67
mative vessels.  In  such cases,  the original  fault
may be in  the assimilating organs,  and in conse-
quence  of the mechanical relations of these to the
formative  vessels,  the  offensive  materials  are
brought to these vessels.
   CXIX.  Second,  a  mechanical or chemical  in-
jury of  any part will induce new  and extraordinary
actions  of the formative vessels for  the restora-
tion of  the part  injured.  Wherever an irritation
exists, a flow  of blood takes  place.   This flow of
blood is  generally  accompanied by an increase of
both sensibility and irritability in the part.   This
flow of blood  is to be referred, not to a vis a tergo,
but to  an active dilatation of the capillaries of the
 part.
   CXX.   Third,  an   irritation  excited  in other
 parts of the  body  may be  extended or communi-
 cated by sympathy to  the  formative vessels,  and
 induce  in them a diseased action.
   CXXI.  Fourth,  by  sympathy likewise the ac-
 tions of the  formative vessels may be diminished,
 or even arrested.
   CXXI1.   In these,  and  perhaps other  ways,
 the formative vessels  may have their functions ar-
 rested, or  diminished,  or  increased, or  modified.
 Of the affections thus induced, the various pro-
 cesses  of  inflammation are  the most  remarka-
 ble.   These  are processes,  in some of which the
 parts are enlarged  by a deposition of various mat-
 ters, by the enlargement of its vessels, and by the 
68
TEXT BOOK.
 formation of new vessels; and in which also vari-
 ous fluids are under different circumstances secret-
 ed.   In  these   processes, the  absorbent  vessels
 sometimes act  a  part; and  in  the termination of
 them new parts are often formed.
   CXXIII.  As  inflammation  is  an affection,  to
 which all the organized  parts of the body are lia-
 ble,  and as it is,  under some of its modifications,
 the  primary affection  in  a very large  propor-
 tion  of all the diseases to  which the body is liable,
 it may be well  to give in this  place some general
 account of its processes.   Five principal processes
 may be distinguished in inflammation, though they
 do not all occur in each case of that disease. They
 may be denominated the formative, adhesive, sup-
 purative, ulcerative and restorative processes.  In
 a regular  inflammation of the  mucous  membrane
 only  the  formative, suppurative  and restorative
 processes occur.  In a regular inflammation of the
cellular membrane, or of any circumscribed cavity,
 the formative and adhesive processes at least oc-
cur;  very commonly the suppurative process fol-
lows, and then the ulcerative and restorative en-
sue.
  CXXIV. The formative process appears to consist
only  in an enlargement of the capillary vessels so
far as can be seen; but it is  highly probable that
there also takes  place some new arrangement, or
other change in the formative vessels themselves,
by which they are fitted to perform the subsequent 
PATHOLOGY.
69
 processes.  It is certain that some little time elap-
 ses after the commencement  of the process,  more
 than seems necessary, merely for the enlargement
 of the vessels.  Likewise, in specific inflammations,
 the diseased  part exhibits a peculiarity of form in
 this stage.
   CXXV. The adhesive process consists, first, in the
 effusion from  the formative vessels of coagulating
 lymph, or of some other fluid which almost imme-
 diately undergoes coagulation, by which  the parts
 opposed  to each other,  may become glued  toge-
 ther; and afterwards, in the extension of vessels
 or formation of new ones,  by the action of  which
 the matter thus first effused  becomes replaced by
 organized parts.
   CXXVI. The suppurative process  consists in the
 secretion by the formative  vessels  of a  peculiar
 fluid, called pus, differing in  its characters accord-
 ing  to the  texture of  the parts affected, and  ac-
 cording  to the character of the inflammation, and
 perhaps according to other circumstances.   Occa-
 sionally, however, instead of pus, other fluids  more
 or less widely differing from  it, are  effused or se-
 creted by inflamed parts.
  CXXVII. The ulcerative process is  performed by
 absorbent vessels,  under various  circumstances;
 but most  especially for opening a passage for pus,
 when this is  formed  on any part  not having a na-
 tural outlet.   When other fluids are  effused or se-
creted instead of pus, the ulcerative  process  rare-
ly, if ever, takes place. 
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   CXXVIII. The restorative process varies accord-
  ing to circumstances.  In some cases,  as in inflam-
  mations of the mucous  membrane,  it  seems to be
  little else than a contraction of the vessels which
  had been dilated,  and a renewal  of the usual se-
  cretions.  In  this  case,  the secretion is gradually
  changed from that  of pus to that of mucus.  But
  in cases, where, from any cause,  a division  has ta-
  ken  place  between parts ordinarily  united, the
 restorative  process  brings  the parts  again  into
 union.   This appears  to be effected through the
 agency of the formative vessels, by  a process ana-
 logous  to that,  by which the growth of the solid
 organs is originally effected.
   CXX1X.  In all these processes various irregulari-
 ties arise, which will be more discussed when treat-
 ing of the subject hereafter.   One  of the principal
 of these is  the  effusion of a  watery fluid instead
 of pus.  This happens in the early stage of inflam-
 mation on  the mucous membrane in some  cases.
 It happens  also on the serous  and cellular  mem-
 branes, when the inflammation is  of a very low
 and slight kind.   It then constitutes a dropsy.
   CXXX. In most inflammations the  disease  is cir-
 cumscribed within limits, which bear a  relation to
 the magnitude  and  violence  of the  central part.
 It is  in this central  part  that  the most important
 processes are performed.   But  in some inflamma-
tions, the disease  gradually leaves the part first
affected, while it extends to the adjoining parts of 
PATHOLOGY.
71
the same texture.   Also, in consequence of acci-
dental causes, there  sometimes occurs a sudden ex-
tension  of inflammation beyond  its natural or ori-
ginal bounds.
  CXXXI. The processes of inflammation cannot
be explained upon the supposition of either an in-
crease,  or  a  decrease  in  the momentum of the
blood.  The most essential part of those processes
appears to be performed by the same extreme ves-
sels, by which the formative functions are conduct-
ed.   Whether the mechanical actions of the ves-
sels in either case determine the result, may well
be made a matter of doubt.
  CXXXI I. In some cases of inflammation,  a con-
stitutional affection is induced, and  this is varied by
many circumstances.  But this  subject will  be
more conveniently discussed in another place.
  CXXXIII. There  are other morbid affections be-
sides inflammation, which  belong to the formative
functions, among which  are haemorrhage, vitiated
secretions and tumours of various kinds.  These,
so far as they call for attention in this course, will
be noticed at  other times.
  CXXXI V. The diseases of the excretory functions
are seldom strictly primary ;  they  are so when any
cause acting primarily on  the excretory organs de-
range those functions.   In the excretory functions
we can see that many diseases may arise analogous
to those of the formative functions.   It has already
been suggested, that if the stomach protrude into 
7'-r>
TEXT BOOK.
 the  intestinal  canal  any  substance,  other  than
 chyme, such substance being an  unnatural stimulus
 to that canal, will  occasion a  derangement of  its
 functions.  These functions are partly those of as-
 similation, partly those of excretion.   As an excre-
 tory organ, this canal  may have  its motions dimin-
 ished or increased,  directly or indirectly,  by the
 substances received  into it.  But  independently  of
 any effect on its motions, the  materials  brought
 into it  may be such as cannot be reduced  to the
 state of ordinary and healthy  alvine feces.   Like-
 wise, the alvine discharges may be changed by the
 secretions, occasioned  by the  unnatural stimulus.
 Hence  we may trace deviations from health in the
frequency, the quality, and the quantity of the alvine
 excretions.
   CXXXV.   The alvine discharges  may  also be
 altered by affections of the secretory organs  apper-
 taining  to the alimentary canal.   This will happen,
 whatever may be the cause of such affections of the
 secretory organs, but will be modified according as
 that cause operates on  the secretory organs alone,
 or at the same time on the alimentary canal.
   CXXXVI.  The frequency  of   the  alvine  dis-
 charges will be diminished by causes of four descrip-
 tions, viz. by a diminution of stimulus, as to quantity
 or quality; by causes  which lessen the irritability of
 that canal; by such as lessen the secretions, which
 are poured into  that canal; and by such as consti-
 tute mechanical obstacles to the  passage through 
PATHOLOGY.
73
the canal.  The frequency of these discharges will
be increased  by causes of an opposite character.
  CXXXVI1. The quality of the alvine discharges
depends on that of the ingesta, directly and indirect-
ly.   Directly, in cases where the articles received
retain any of their characters unchanged, or under-
go fermentation instead of  digestion.  Indirectly,
where the articles  received induce any change in
the secretions of the  abdominal organs.  Some ar-
ticles increase the watery secretions only,  as  the
neutral  salts.   Others  induce  an  increase  in  the
secretion  of mucus;  others  in that  of bile.
  CXXXVIII. The quantity of the alvine discharges
must ordinarily depend on the quantity of food un-
digested,  and  on that  of  the  secretions.   The
quantity at a single evacuation will  be influenced
by the frequency,  and  by the energy with which
the large intestines act  in discharging the load ac-
cumulated in them.
  CXXXIX. But, the ingesta being the same, the
evacuations will vary according to the state of the
stomach and  intestines.  Thus, proper vigour or
the want  of  it in  the alimentary canal, must have
a great  influence.  Also, if  from inflammation,  or
any other cause, the  canal  be rendered unusually
irritable,  a common stimulus will  produce all  the
effects of a great or extraordinary  stimulus  on the
healthy canal.   Hence  the  evacuations will vary
in frequency, quantity and quality.   The secretions
produced by the inflammation  will  of course be
              10 
TEXT BOOK.
discharged, either by themselves or in mixture with
the other  contents  of  the  canal.   In some cases
blood  may be discharged from the part diseased.
The effects of inflammation  in the alimentary canal
are greatly varied by the violence, extent and seat
of the disease, and by the texture affected.   There
are some peculiarities  in the alvine discharges, in
a diseased state of  the canal, which might not at
first  be  anticipated.  Thus,  while  the canal is
loaded with  feces,  the discharge will  consist of
blood, or bile, or mucus unmixed with fecal matter.
When the  discharge is  blood or mucus,  it may be
supposed that  it is derived from the rectum, or
from the lower part of  the colon, where there may
not be any  feces  at  the  time.  But sometimes
these fluids are derived from a higher part of  the
intestine.   In the case of bile,  it  must always be
derived from the small  intestines.   That the bile
should not  be mixed with the fecal  matter can be
explained only  on the supposition, that the fecal
matter is in a state  in  which  it will  not readily
permit the mixture of any fluid with it; and that
at the  same time the bile is so acrid as to occasion
rapid and violent contractions of the intestines to
propel it.
  CXL.  In the excretion of urine, deviations from
perfect health  may arise  from  various  remote
causes, viz. from variations in the ingesta, from im-
perfect assimilation, from a morbid state of the kid-
neys, or of  the other organs belonging  to the uri- 
PATHOLOGY.
1U
 nary apparatus,  or  of organs  closely connected
 with those, or lastly from sympathy.
  CXLI. From these several causes singly, or acting
 in conjunction, the urine itself may be increased or
 decreased in quantity, may have its colour changed
 may  be turbid  when discharged, or become so
 after standing a  short  time, and  the  matter sepa-
 rated may form a sediment or remain suspended in
 the urine.
   CXLII. The  urine  is increased in quantity by
 taking  into  the stomach an unusual quantity of
 liquid, or certain substances  which  act especially
 on the kidneys, such as vegetable acids; by a dimi-
 nution of the evacuations from the skin; by certain
 passions of the mind;  and in certain diseases, by
 causes not satisfactorily ascertained.
   CXLIII. The urine is diminished in quantity by
 some causes the opposite of those which increase
 it; such as diminution  in the quantity of liquids
 swallowed, by increased discharge from  the skin,
 &c.  Likewise it is diminished  under certain dis-
 eases,  as by inflammation either  chronic or acute;
 especially by that inflammatory affection which oc-
 casions dropsy; and by diseases  affecting the  kid-
 neys themselves.
   CXLIV.  The  colour of the urine depends on the
greater or less quantity of  water, and on that of
certain ingredients which naturally belong to it, or
which are formed under disease.  But the consi-
deration of this subject in detail would lead us too
far. 
76
TEXT BOOK.
   CXLV. The matters separated from the urine,
 whether mucus alone, or the saline contents of the
 excretion,  remain suspended or form  a sediment
 according to the specific gravity of the fluid.   The
 red sediment, so common in inflammation, consists
 principally of  the lithates of ammonia and of soda,
 with a large proportion of the colouring matter of
 the  urine.  The white sediment consists princi-
 pally of the ammoniaco-magnesian phosphate.
  CXLVI.  Respecting the changes in the evacua-
 tions from the skin  and  lungs  under disease, our
 knowledge is not very  precise.  The sensible per-
 spiration is diminished  under exposure to cold and
 when at rest,  and  increased under  the opposite
 circumstances; and similar changes take place un-
 der disease.  The changes which  occur  under dis-
 ease may  be referred,  in  many instances,  to sym-
 pathy of the skin with the diseased organ; but in
 some cases, probably the cause may be a failure in
 the functions of assimilation,  whence  a change in
 the composition of the blood is produced.   In all
cases the  immediate cause is a change in the ac-
 tions of the excretory vessels.  A fulness of the
cutaneous  capillaries is not  immediately followed
by increased sensible perspiration; but  is so ulti-
 mately in  most instances.
  CXLVI I. The morbid changes, to which the ani-
 mal  functions  are liable, must next be examined.
 It has already  been stated that the vital properties,
 and especially the irritability  and sensibility,  may 
PATHOLOGY.
77
be  temporarily increased  or diminished by the
direct agency of foreign substances.  Moral causes,
or causes operating on the mind directly, may affect
the animal  powers. A change in these powers may
of course occasion a change in the functions which
depend on  them.
  CXLVIII. But in a large proportion of cases, we
must  refer  the diseases of  the  animal  system to
primary  changes  in the organic functions.   It»is
most especially to changes  in the state of the ves-
sels, which  belong to the  animal  organs, that  we
must attribute  most of the grave diseases of the
animal system.   But  in  some cases  these diseases
appear  to  arise solely from  sympathy  with the
organic system.
  CXLIX.  In whatever mode a primary disease is
produced in any one  part  of the animal system,
the other parts of the same are liable to be affect-
ed so far as their  functions are connected.  It is
especially when the brain  is the seat  of disease
that such secondary affections are produced.
  CL. Diseases of the  mind are  in many  cases
manifestly referrible to affections of the  body; but
there are cases, in which such a reference cannot
be  made with   confidence.   In  such cases  there
must be a doubt, whether the disease of the mind
is original, or whether it is occasioned by a disease
of the body, which we cannot detect.
  CLI. In  those affections of the animal system,
which depend on  the state of the vessels belong- 
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TEXT BOOK.
 ing to the animal organs, two opposite states of
 that system are produced  by the diseased state of
 those vessels.  This is  most  remarkable, where
 the  vessels  of  the brain  are  affected.  First,
 an increased determination of  blood to the brain,
 and especially when  the small  vessels are particu-
 larly affected, occasions pain, or distress, or a sense
 of confusion in the brain, accompanied often by in-
 creased sensibility in  the organs of sense, and a ten-
 dency to violent,  irregular, and  often involuntary
 actions in  the  animal muscles.  Secondly,  when
 the quantity of blood accumulated in the brain is
 greatly increased, or when the increased vascular
 fulness has been  followed  by effusion of  any kind
 from  the  vessels, then  the  brain  becomes com-
 pressed,  and effects  of  a different kind  ensue.
 These are a diminution, or  loss  of sensibility in one
 or more parts, and a suspension of  all actions, vo-
 luntary or involuntary, in the animal  muscles.  It
 frequently  happens   that  a suspension of  action
 takes place in one part,  as on one side, while in-
 voluntary actions take place in another part.  This
 arises from a compression of one part of the brain
 and an irritation of another part.
  CLII. The suspension  of sensation and volun-
 tary motion may arise from pressure on the brain,
however induced.  It does  not  appear that a cer-
tain amount of  pressure will  always  produce the
same effects.  This may be explained by consider-
ing, first,  that something will depend on the part 
                   PATHOLOGY.                79
 of the brain particularly compressed;  and second,
 that, so far as the pressure operates on the whole
 bram,  its effects will be  greater or  less, as the
 compression takes  place  more  or less  suddenly.
 When the  pressure is  produced  very gradually,
 the brain becomes  accommodated to it, either by
 the absorption of some part, or in some other way.
   CLIII. The consequences  of  pressure  on the
 medulla spinalis, or  on the nerves, are somewhat
 similar to those  of  pressure on the brain.  In re-
 gard to the nerves, however, it  must be noticed
 that they are less liable to compression than either
 the brain or spinal  marrow;  sinces these last are
 inclosed within cases  of bone, while  the nerves
 generally lie among the soft parts, which yield
 somewhat to pressure.   The nerves are,  however,
 liable to be compressed  against a  bone by tumors,
 and likewise to be  compressed by the effusion of
 coagulable lymph around them, as in the adhesive
 process of inflammation.
   CL1V. The nerves of sensation are subject to a
 certain  affection,  which is manifested only by pain.
 This affection has received  the name  of neuralgia.
 In many cases  it has the appearance  of an  idio-
 pathic disease of one or more of  the nerves.  In
 some cases it is a symptomatic affection; and, gene-
 rally, pain is symptomatic.  Neuralgia  may be di-
 rectly produced  by some  inflammatory  or other
 vascular affection of the nervous  trunk or twigs.
But there is not any evidence  that this is the case. 
80                TEXT BOOK.
   CLV.  Increase and diminution  of sensibility in
 particular nerves, and also its abolition, arise from
 various local effections in  the organs to which  the
 affected nerves belong;  and likewise by sympathy
 from the affections of distant organs.   Pain and in-
 creased  sensibility often occur together; but they
 are not inseparably united.
   CLVI.  The muscles, as well as  all other  or-
 gans, are diseased in consequence of affections of
 the  blood-vessels, which belong to  him.   But in
 some cases there appears also to be an original
 affection of the muscles.  At  least  the power of
 contraction is impaired, or  the contractions take
 place irregularly,  without any  evident agency of
 either the vessels belonging to the organic system,
 or of the brain or nerves.  Use and  disuse of the
 muscles, especially the latter when long continued,
 have a direct effect  in occasioning disease in those
 organs.   It would seem, also, that the long conti-
 nued internal use of  alcohol, and that some mine-
 ral substances,  long  applied  to  the body, occasion
 directly some  change in the power  of motion in
 the muscles.
  CLVII. Voluntary motion, or the  action of the
 muscles under the influence of the will, is arrested
 or modified by  diseases of  the brain,  or of the or-
gans intermediate  between the  brain and muscles.
 Voluntary motion  is  also prevented  in particular
muscles by sympathy with distant organs, without
 any obvious affection  of the nervous system, 
I
                   PATHOLOGY.               81
    CLVIII.  Involuntary motion, viz. in the organic
 system, is no doubt affected by the original diseases
 of the muscles, just  as voluntary motion is.   But
 the dependence of the involuntary or organic mus-
 cles on the nervous system is not the same as that
 of the voluntary or animal  muscles.  Yet the in-
 jury  or division of nerves supplying the  organic
 muscles will influence such  muscles,  inasmuch as
 such injury deprives them of the salutary influence
 of sympathy with  other organs.  There  may also
 be a direct effect from the injury of the nerves of
 such  muscles, as from the injury of any part with
 which they are connected.
   CLIX. The  functions  of the voice, dependant
 on the vigour and integrity of  many parts, are lia-
 ble  to be  affected  by  various  causes.  Among
 these  are organic  affections of the  nose,  mouth,
 fauces, larynx, &c.; affections of the nerves of  the
 larynx; and  sympathy both with the whole system
 and with  particular parts.   From these causes the
 voice may be  affected in its  tones,  volume, and
 strength,  and the articulation in its distinctness.
   CLX.  The  various   appetites,  inasmuch  as
 they are  dependant at once  on  the organic and
 animal systems,  are influenced  by changes in each
 of those systems.
   CLXI.  We  have  been  engaged in reviewing
the different functions, and considering  in what
ways they may be  most remarkably diseased.  It
is  probable that they are susceptible of other dis-
             11 
82
TEXT BOOK.
 eases, of  which we have  not  any just conceptions.
 Let us now pursue a different course, and inquire
 what are the diseases, which are known to occur in
 the human  subject, and which have  been distin-
 guished  by clinical practitioners.   These  are nu-
 merous,  and yet  they probably may be reduced,
 with  the consent of all, to a few classes.
   CLX1I. In  distinguishing and naming diseases
 men would first have  reference to  symptoms, and
 Would afterwards  learn to  attribute  these to
 the several  primary  affections; and then   they
 would think  only of  distinguishing  these primary
 affections  from  each other.  Thus, headach would
 be called a disease, vomiting another, diarrhoea an-
 other.  But it  might be presently discovered, that
 all these originate in an affection of the  stomach;
 and then that  affection would  be regarded as the
 disease, and the headach, &c. as symptoms.
  CLXIII.  The different  primary affections, to
 which the human body is subject, may all proba-
 bly be included  in  the following classes,  and  per-
 haps some of these may be unnecessary;  viz.
  Phlegmasia?.            Spasmi.
  Hemorrhagic.         Dysorexiae.
  Profluvia.              Vesaniae.
  Febres.                Adynamia.
  Dolores.
  CLXIV. But from  a regard  to convenience, it
may be well to add the following classes, viz.
  Morbi  organici.
  Morbi  ex adventitiis in corpore inclusis.
  Mimoses. 
PATHOLOGY.
83
  CLXV.  But it is not possible  to  prove that
this, or any other number of classes, will properly
include all the diseases of mankind.  The opinions
formed  by different persons  on  this subject will be
founded on  the different  pathological principles
they may adopt.  While it is impossible to demon-
strate the truth of any system of pathology, it will
be impossible  to make  men agree on  any system
which is proposed.
  CLXVI. A methodical arrangement of diseases,
founded  on any  such  principles,   will not  meet
with universal approbation.   Is there not  then any
ground  on which  a nosological  system can  be
founded,  analogous   to  the methodical  systems
adopted in the various branches of  natural history?
So  long as we confine ourselves  to  the objects
which  can be  demonstrated or pointed  out, we
may adopt such a system.   Symptoms  are the im-
mediate objects of our  knowledge, and they will
admit of a  systematic arrangement.
  CLXVII. Among the many nosological systems
which  have been  published, that by the learned
John M.  Good seems  entitled to a  preference,
among other reasons, for this; that the arrangement
has  a reference to  the actual phenomena of dis-
eases, or to symptoms, more than that of any other
similar work.   In the practical part of this course,
Good's  system will  be  followed,  and  then  some
evidence will be offered in support of  the remark
last made. 
THERAPEUTICS.
   CLXVIII. This division of the science of medi-
 cine relates to the treatment  of diseases; or, more
 strictly, to the treatment of persons under disease.
 Its ultimate objects are three; of which sometimes
 one only is  regarded;  sometimes two,  and  some-
 times all  three  are regarded at  the same time.
 To effect its objects,  two different methods may
 be  pursued; of which  one  is called  active,  the
 other watching,  or expectante.  There is likewise
 another distinction in  respect  to  the method of
 treating diseases,  which  relates to the considera-
 tions which determine  the  physician  in his choice
 of  remedies.  The distinction here referred  to is
 that of the rational and the empirical modes. The
 former  mode is  preferable;  but when our know-
 ledge does not enable us to apply it, we must avail
 ourselves of any resources offered by the latter.
  CLXIX.  Whatever mode is  pursued, it will  be
done  to more  or  less  advantage precisely as our
knowledge of the  pathology  of the disease under
care is more or less perfect.   For rational practice
especially, it is requisite to distinguish in every case
the symptoms, the  proximate  cause and the remote
causes;  and especially to be able to anticipate the 
THERAPEUTICS.
85
  probable course  and event of the disease.   From
 a consideration of these circumstances, the rational
 practitioner adopts certain  intentions in  his  treat-
 ment, by which he hopes and designs to afford re-
 lief to the patient.   Or it may be said, that a con-
 sideration of these circumstances furnishes an indi-
 cation of  the course  to be pursued.   The empiri-
 cal practitioner does not adopt any intention in the
 technical sense,  except the general  one  of reliev-
 ing the patient by means, which have been thought
 beneficial in cases apparently similar.
   CLXX.  Although  indications  may be derived
 from different sources, they are  not equally satis-
 factory from them all.   They are least satisfactory
 when derived from the symptoms only, as these may
 often be  salutary in their tendency, however trou-
 blesome they may be at the moment.  On this point
 we cannot judge  correctly, when the causes are
 unknown  to us.   Yet, when symptoms  are  very
 distressing, and still more if they be attended with
 apparent danger, we  follow the indications  they
 furnish, though with all possible caution.   In some
 diseases  experience will justify such a course.
   CLXXI.  Indications derived from  the  remote
 causes will  be more safe than  those derived from
 symptoms.  But  they cannot always be  fulfilled;
 nor, when fulfilled, does relief always follow.  In
 some diseases relief cannot be obtained until the re-
 mote causes are  removed; but in others  a train of
consequences follows them,  which  is  not  arrested
by their  removal. 
86
TEXT BOOK.
  CLXXII. Indications from the proximate cause are
 the most safe and satisfactory.   In some cases this
 cause  may be  removed;  in  others, where  this
 cause may be said to consist in a succession of pro-
 cesses, these may be interrupted.   But even these
 indications cannot always be fulfilled  with impu-
 nity ; and  in  some cases the  means are wanting.
 The indications  may  be clear,  but  our power may
 be limited.
  CLXXI 11.  The means employed for the cure of
 diseases are various.  They consist in the removal
 of some material  from the body, or in some opera-
 tion on the body, by surgery;  or in the  application
 of some  medicinal agent  to the body; or  in some
 operation on the  mind ; or in the regulation of the
functions by diet  and regimen.   The  principal  sur-
gical remedies employed in the  practice of  the
 physician, as distinguished from surgery in the fa-
 miliar sense of the term, are blood-letting and fric-
 tion.
  CLXXIV. The mode in which blood-letting ope-
 rates to relieve disease has never been  well ascer-
 tained. There cannot be any opinion  generally re-
ceived  on this subject, while  the mode, in which the
circulation is maintained, continues to be a matter of
dispute.   Without referring to the various opinions
entertained on these points,  the following remarks
will be offered as an attempt to explain the effects
of blood-letting.
  CLXXV. First, the effect  of the operation on the 
THERAPEUTICS.              87
mind will often  for a short time, and  in some in-
stances for a long time,  modify  the effects of the
loss of  blood.  Second,  the effects of bleeding are
in some considerable  measure  modified  by  the  ra-
pidity or slowness, with  which a given quantity of
blood is taken away.   Third, when blood is taken
from a person in health,  the  effects will l  diffe-
rent  from those on  a person under disease;  and
especially if the disease be one, in which there is
an unequal distribution of blood in the sanguiferous
system.  Fourth, both  in health  and disease the
effects  will  no doubt vary somewhat  in different
individuals; as in one the heart  may be propor-
tionally more or less vigorous;  and so in respect to
the  other  organs  of  the  sanguiferous  system.
Fifth, when blood  is taken   from a large vein in
health, there will be produced different effects on
the heart and on the bloodvessels ;  effects modified,
as above suggested, by the constitution of the sub-
ject.   The  heart will receive less blood at each
diastole, or else will  have the diastole lengthened.
So far  as regards the heart, therefore, bleeding-
will  diminish stimulus.   Meanwhile  the arteries
and veins will contract; inasmuch  as these vessels
are always precisely  full.  This contraction, as re-
spects the arteries, will probably be effected by an
elastic power to a certain extent; but, when the
loss  of blood is  very  great, the contraction will be
effected by a vital  power.   As the veins do not
appear to possess any elasticity,  their contraction 
88
TEXT BOOK.
must probably be effected by a vital power.   The
capillaries appear not to contract so rapidly as the
larger vessels;  but eventually  they contract in
their proportion, so that the blood  becomes equal-
ly diffused  throughout  the  sanguiferous  system;
and,  consequently, the  loss operates equally  on
every part of that system.   Sixth, in general, when
the blood is distributed  unequally, or in undue pro-
portions, the ultimate effect in bleeding will be to
lessen the  proportion  of blood in  those parts,
where it is accumulated more than  in other parts;
or in other words,  to  restore the  balance of the
circulation.  This appears  to accord  with facts
often observed,  even though the mode, in which
the effect is produced,  may not admit of a satisfac-
tory explanation.   The especial effects last noticed
may be explained in cases of  active dilatation of
the vessels in  this way.  The bloodvessels always
contract  exactly upon their contents.   When they
enlarge preternaturally  in any  part, and thus are
enabled  to  contain  more  blood, they  gain  this
blood at the expense  of some other  part.  This
rarely happens to a considerable  extent, when the
quantity  of  blood  in the body is  much less than is
natural.  If it has happened,  when the blood was
in due quantity, and the quantity of  blood be after-
wards much diminished, there may  be supposed to
be a contest between the vessels performing heal-
thy functions  and those performing  morbid  pro-
cesses, which shall yield the greatest proportion of 
THERAPEUTICS.
89
X
  blood.   It may be, that it  will suffice if  they yield
  their blood  in due proportion.   But if this be not
  sufficient  to keep the  vessels,  which are engaged
  in the necessary and healthy operations of the  sys-
  tem duly supplied, the vessels engaged in the mor-
  bid  process will  yield  their  blood, or contract in
  greater  proportion than the other vessels;  because
  their actions are not governed by so strong a ne-
-  cessity,  as those  of the other vessels.   The only
  exceptions will be in  the  case of such debility in
  the vessels of the diseased  part as to prevent their
  contracting; or in  the case of  so strong an  irrita-
  tion from  the  influence of some morbid cause in
  the diseased  part, as  to  be equal to the natural
  tendencies, or necessity for action  in the vessels of
  the healthy parts.   Seventh,  in  cases  where  the
  dilatation  is passive, as commonly, if  not  always,
  happens when the blood  is accumulated in  the
  veins, the diminution of the mass of blood lessens
  the resistance to action ;  and then the dilated ves-
  sels  are commonly able  to  contract  and propel
  their contents, so as to reduce themselves to their
  ordinary size.   In such cases the arteries may  be-
  come more full after bleeding.
    CLXXVI. The effects  of local bleeding,  or of
  bleeding from the small vessels, as by leeches, or cup-
  ping, are generally thought to be much greater in
  the vicinity of the part operated on than upon the
  whole system.   This has been denied by some per-
  sons; but more on the ground of  a difficulty in  ex-
             12 
90
TEXT BOOK.
 plaining such local effects, tnan on that of observa-
 tion. If the effects be admitted, the explanation must
 probably be found in  the partial  independence of
 the capillary system.  That there is often a local
 turgescence  in the  capillaries appears to be cer-
 tain; and  it is manifest  that  no local turgescence
 can arise from the influence of the  heart.  It may
 well happen, then, that a local  bleeding may di-
 minish  the  blood  in  the capillary vessels  acted
 upon, and on those in  their vicinity,  more than in
 any other part of the  body.   In the  case of spon-
 taneous  local bleeding,  the effects are often very
 great from a small  evacuation.  This is best ex-
 plained  on  the supposition,  that  there exists an
 erethism in  the  part, which is removed by the
 spontaneous  bleeding, just as  the erethism of the
 mamma  is relieved by the discharge  of milk, and
 that  of  some other organs, in a  mode obviously
 analogous.
   CLXXVII. Friction, pressure, beating, shampoo-
 ing, &c. have often been highly lauded, as remedies,
 by those  who have employed them fully, and have
 been more  or less valued  by most  practitioners
 of medicine and surgery ; yet their modes of ope-
 ration have not been very well ascertained.   Pro-
 bably these different operations do all produce the
 same effects.  Some share of  the  influence  they
 produce,  is probably effected  through the medium
of the sensations  and  that  of the mind.  These
will vary according to  the kind of operation,  and 
THERAPEUTICS.
»1
 according  to  the character  and circumstances  of
 the patient.   The direct effects on  the body will
 no doubt  in some  cases  be limited  to the skin, as
 where oentle  friction only is  employed ;  in others,
 extend  to  the muscles or  other subjacent parts.
 The effects of gentle friction on the  skin are, pro-
 bably, to solicit  more blood  to that  organ, and  to
 promote the healthy action of its vessels; and thus
 to induce an increase in  its warmth  and in its se-
 cretions.  Analogous effects  may be produced on
 the subjacent  parts by hard rubbing,  and thus may
 be derived  benefits similar  to  those of muscular
 exercise.
   CLXXVIII. The medicinal agents applied to the
 body operate upon the principles stated in the phy-
 siological part of this course.   From a regard to
 their apparent operation on the diseased body, these
 agents are conveniently distinguished under  the fol-
 lowing,  or  similar names, viz. stimulants, sedatives,
narcotics, antispasmodics, refrigerants, alteratives, as-
 tringents, tonics, emetics, cathartics, diuretics, diapho-
 retics, emmenagogues, expectorants, sialogogues,  er-
 rhines, epispastics, escaharotics,  antacids, antilithics,
 anthelmintics,demulcents, and emollients* There will

  * This list is adopted from Dr  Bigelow1s Sequel to the
 Pharm. of the U. S. pp. 18—25.  The terms are employed
by me, as by him, from a regard to  convenience; and the list
may  be diminished or increased without  any difference of
opinion as to the  real mode of operation of the remedies re-
ferred to. 
92
TEXT BOOK.
 be some convenience in considering remedies under
 these  general  names;  but  a  useful  knowledge
 of the powers of medicinal substances cannot be at-
 tained without attending to the peculiar properties
 of the  individual  articles employed.   But a par-
 ticular consideration of this  branch of  the subject
 is unnecessary, as it is the peculiar business of the
 Professor of materia medica.
   CLXXIX. It is  sometimes possible  to cure dis-
 eases,  and often to mitigate them, by operations on
 the mind.  Every sagacious and humane physician
 avails  himself of this power,  and  that,  sometimes,
 without any very precise  and settled plan.  This
 object will be more certainly attained, when we
 act upon principles previously considered  and set-
 tled.   The common empirics avail themselves of
 this power  to great advantage in  many cases.   It
 is no doubt true,  that they often abuse  the power,
 and that they resort to methods unworthy men of
 pure  and elevated characters;  of methods, the
 berefitof which is often transient,  though brilliant.
 But, on  the other  hand,  the regular practitioner
often fails to derive the fair and proper  advantage,
 which  he might obtain by an  influence on the mind
of the sick.
   CLXXX.  Under this  head it  may  be stated
briefly: 1.  It is proper to remove all undue and un-
founded fears, whether they  arise  from  the appre-
 hension of improbable evils, or from magnifying such
as are inevitable; 2. It is proper to encourage the 
THERAPEUTICS.
93
fortitude of the sick and suffering,  and to suggest
all the motives to patience.  3. It is proper to as-
sume a cheerful air  in  all cases, avoiding however
all levity, and  especially in cases of danger, or of
great suffering.   4.  It is of the utmost consequence
to satisfy the  patient  that you are  desirous to un-
derstand his case,  to show a proper  sympathy in
his sufferings,  and without ostentation  to evince a
sincere desire to afford  him relief.   5.  It is often
proper to make such arrangements  as will  occupy
the patient's mind, so as to divert his thoughts and
to remove  anxiety and despondence.  6. It  is  pro-
per to employ trivial remedies, on the direct effects
of which no  reliance can  be  placed, when these
can  be employed so as  to sustain the patient's
hopes,  and thus  to promote his  recovery;—or
when they will induce him to make exertions, sa-
lutary in their  nature,  but to which he cannot be
prompted by more rational methods.
  CLXXXI. The influence of diet and regimen in
regulating the health is in many instances more im-
portant than that  of the common medicinal  agents.
Some general remarks  only will be  made on these
as on other subjects.   First,  of diet.   The influ-
ence of articles of diet, whether they be nutritious,
or cordials,  or  condiments, will  be  manifested in
the alimentary canal,  in the  general  system,  and
occasionally in some  particular parts  other than the
alimentary canal.
  CLXXXII.  As respects the alimentary canal, ar- 
94
TEXT BOOK.
  tides differ as they are more or less easily digested,
  as they are more or less stimulating to the stomach
  and organs of  digestions, and  as  they exercise di-
  rectly or  indirectly  more or less  influence in pro-
  moting the alvine discharges.
   CLXXXIII.  All arrangements  of the articles of
 food as being more or less easy  of digestion, are
 fallacious, unless due attention  be paid to the age,
 constitution, habits, state of health, &c. of the indi-
 vidual  concerned.   But in  all cases  it is important,
 that  such  food  be taken  as can  be digested, and
 that  the quantity be not greater  than can  be di-
 gested ; for any article  may be  the  cause of great
 derangement  in  the alimentary  canal  and  else-
 where,  if not digested.  This  is peculiarly true
 when any  part of the intestines is  in a state of dis-
 ease, or is unusually irritable.   For food, though
 the natural stimulus to the stomach, is  not so to
 the intestines;  and will, therefore, act on  them
 somewhat  as a foreign substance does in the cellu-
 lar membrane.
   CLXXXIV.  In acute  diseases,  and  in  other
 cases where the  powers of digestion are temporarily
 suspended, either  nearly or entirely,  it appears to
 be best  to  administer  food only in  a liquid  form,
 and of such kind as is least stimulating.   The ad-
 vantage of  the form  appears  to be,  that  (he arti-
cles may be easily propelled, if  not digested ;  and
that they may not be injurious to the intestines.  It
is for this last reason, in part, that the food, which 
                 THERAPEUTICS.         /    95
is  least  stimulating  is  preferred.  This  circum-
stance,  however,  is  likewise important in respect
to the whole system in acute diseases.
  CLXXXV. On  the contrary in  dyspepsia, whe-
ther existing alone, or in connexion with a chronic
disease, it is often important to administer food in a
solid form, and of a character somewhat stimulat-
ing.   This would be useless,  if the powers of di-
gestion were entirely lost;  but if  not, such food is
found  by experience to be  most digestible.  It
may then happen that  in a chronic disease, in re-
spect to which, considered alone, we should prefer
the least stimulating food,  we  may be  obliged by
the state of the digestive powers to exhibit food of
the most stimulating character.
  CLXXXVI. It happens in many cases of disease,
that it is very important  to diminish the excitement
of the vascular system;  and on that account very
little food  should be allowed, and that should be
of the least  stimulating  kind.  This  will happen,
when  the heart  itself or any of  the large vessels
is the seat of any organic affection; likewise, when
an  active inflammation  exists in  any part of the
body.   Under the same circumstances  condiments
and cordials,  especially  the latter, are commonly
to be avoided.
   CLXXXVII.  On  the  contrary,  in many cases of
exhaustion and debility, where none of  the circum-
stances above-mentioned exist, it is important to re-
plenish the vessels, and to sustain their actions until 
 96                TEXT BOOK.
 they are replenished.   In these cases, the most nu-
 tritious food, rendered grateful by condiments and
 the best cordials, are very usefully employed.  The
 cordials are also useful in instances where  there is
 a great temporary depression of the vital  powers
 without any local affection.
   CLXXXVI1I. Secondly, of regimen.  In a large
 proportion of cases, other circumstances must be re-
 garded besides medicine and diet, if we would make
 our cure certain, safe  and speedy.  The  evacua-
 tions  are often controlled  by  a proper government
 of the  patient's  conduct.  His  place  of residence,
 his clothing, his  exercise and  rest,  his sleeping and
 watching,  and  the  passions  and emotions of the
 mind  will  all of  thern call for the  attention cf the
 physician, and should, as far as possible, be direct-
 ed by him.  All  these circumstances  must be de-
 termined  by the general principles of physiology
 and of hygiene,  modified in each  case by a consi-
deration of the previous habits  and present state
 of the patient.
r«"i6 0  6^'