ANAESTHESIA. 
]/ BY 
\Vr. C. BARRETT, M.D., D.D.S., M.D.S., 
BUFFALO, NEW YORK. 
HEAD BEFORE THE AMERICAN DENTAL ASSOCIATION, AT 
ITS TWENTIETH ANNUAL MEETING, HELD IN 
BOSTON, MASS., AUGUST 5th. 1880. 
FROM THE TRANSACTIONS OF TI TIOS. 
P II I L A D E L P II 1 A : 
T R U S T E E S OF SAMTJ E L S. W 11T T E. 
1881. ANAESTHESIA. 
A LL through the centuries of time man has been endeavoring to 
find some way of escape from the penalties of broken law; to 
avoid the pain naturally consequent upon disordered function, or the 
lesions produced by accident; but until the nature and action of the 
so-called anaesthetics became known, his efforts were futile, or at the 
best but incomplete. 
There are a number of different states which may be induced in 
which, while the condition remains, patients are insensible to pain, 
such as coma, syncope, anaesthesia, and sleep. The first three are 
pathological; the last is the normal condition of recuperation and re- 
covery of wasted neural force. All these phases or conditions de- 
pend upon the nervous supply, and are induced by normal or abnor- 
mal nerve-currents. 
There are certain drugs whose office seems wholly connected with 
the nervous system. Of these are nervous stimulants and sedatives, 
and a distinct class which are denominated anaesthetics. The mys- 
teries of nerve force or of nervous supply have never yet been bared 
to human knowledge. We experiment and deduce so-called laws, 
but those laws are not general; they have so many exceptions that 
at present it is impossible to say how certain of these principles effect 
their marvelous purpose. Of some agents we know that their action 
is entirely reflex, and that the nervous system is affected through cer- 
tain definite organs. But there are others of which this seems not to 
be true, and the scientific world is now engaged in the effort to solve 
this mysterious problem. So far, comparatively little progress has 
been made, and since the day of Claude Bernard, who advanced the 
theory that such agents as directly affect the nervous functions do 
it by a coagulation more or less complete of the protoplasmic ele- 2 
ANAESTHESIA. 
merits of nerve tissue, nothing but barren hypothesis has been 
advanced. 
Of the various impressions which medieinal agents may exert 
upon nervous function, let us confine ourselves tb that state called 
anaesthesia, as the most important to the practitioner of dentistry, 
only considering stimulants and sedatives as they ma}’ be incidentally 
connected with our subject. 
Narcosis or anaesthesia may be considered as a state of paralyza- 
tion of the sensory nerves, with insensibility or complete stupor. It 
is the suspension of sensation, and is the effect wrought by a number 
of agents, the most complete and powerful of which is hydrocyanic 
acid. But there are certain inciting agents or conditions aside from 
the direct action of drugs. In warm-blooded animals anaesthesia or 
insensibility to external impressions is produced by cold, or the lower- 
ing of the bodily heat, and in cold-blooded animals by the raising of 
the temperature. We are all familiar with the effect produced upon 
our own members by a long exposure to a low temperature, and we 
are conversant with the dreaded drowsiness which benumbs the facul- 
ties of a freezing person, which renders him insensible to pain and 
prompts him only to lie down and sleep. The same effects are pro- 
duced upon a cold-blooded animal if the temperature be unduly raised. 
Experiment 1.—Place a frog in a vessel containing water of 100° F., and it 
soon exhibits the same inertia and desire for sleep as the freezing mammal, and 
in a little time becomes quite insensible. If it be now removed to cold water 
it speedily recovers; but if long continued in the warmer fluid it dies. 
The most common agents used to produce an artificial anaesthesia 
are nitrous oxide gas, chloroform, sulphuric ether, and bromide of 
ethyl. But carbonic acid, carbonic oxide, coal gas, olefiant gas, fumes 
of lycopodium giganteum, aldehyde, acetone, and other gases, when 
inhaled, may produce a like insensibility to external impressions. As, 
however, they are not commonly used to induce anaesthesia, we will 
not now particularly consider their properties. 
How do these agents produce their characteristic effects? As I 
have said, this is a question which has not, so far, been satisfactorily 
answered. But, though no one can give an undisputed demonstra- 
tion of their manner of action, there are certain phenomena the con- 
sideration of which may assist us in coming to some conclusion upon 
the subject, and these we will examine. 
Claude Bernard says that an anaesthetic is a drug which produces 
a direct impression on nerve tissue. Prof. Anstie sa}7s that the pecu- ANAESTHESIA. 
3 
liar effects are through a modified blood-supply, or by alteration of 
nutrition, and most modern physiologists agree with him. Which is 
right ? It is certain that anfestbetics are amenable to that law which 
is universal in therapeutics,—that to produce its characteristic effect a 
drug must be first introduced into the system, and that the method 
of its diffusion is through the blood. 
Experiment 2.—Expose the lumbar nerves of a frog by raising the point of 
the sacrum. Pass a ligature around the whole body, excluding these nerves, and 
then inject the posterior extremities with woorari, or strychnia, or chloroform, 
and it will bo seen that the anterior extremities are not paralyzed or convulsed, 
showing that the influence is not extended through the nerves. 
To produce anaesthesia it is also quite true that there must be suf- 
ficient of the agent existing in the blood at one time. Ether and chlo- 
roform are eliminated almost entirely by’the pulmonary mucous 
membrane. If of either a much more than sufficient quantity to pro- 
duce anaesthesia be slowly injected directly into an artery, the char- 
acteristic effect is not seen. 
Experiment 3.—Into the peritoneal cavity of a cat was very slowly injected 
spi of Squibb’s chloroform, and the animal was but little affected. At another 
time I quickly injected gi of the same, and complete narcosis ensued. 
When the drug is administered slowly the immunity is due to the 
fact that it is eliminated before it has time to exhibit its character- 
istic effect. Not enough is existent in the blood at one time to induce 
narcosis. 
The most characteristic effects of common anaesthetics are produced 
when their vapor is inhaled, because it is thereby most readily intro- 
duced into the blood. The immense surface (about 1400 square feet) 
presented in the lungs of man brings the blood in osmotic contact 
with so much of the vapor that the pulmonary circulation is com- 
pletely charged with it, and this is carried immediately to the heart, 
and thus distributed to the remotest part of the system without an 
opportunity being given for its elimination. But if an anaesthetic 
agent be injected into the venous circulation, little effect is produced, 
because it is canned directly to the heart, and from thence through 
the pulmonary artery to the lungs, where it is at once eliminated, 
never reaching the arterioles at all. 
Experiment 4.—Into the jugular vein of a cat, previously anaesthetized, in- 
ject of sulphuric ether, and the animal will soon recover from the narcosis ; 
while if it be injected into the carotid artery, it will deepen the influence. 
We may then consider it demonstrated that the drug must be ex- 
istent in the arterial blood in sufficient quantity at ope time, in order 4 
ANAESTHESIA. 
to produce its characteristic effect. Now follows the important ques- 
tion : Is it simply held in solution in the serum of the blood, or is it 
conveyed by the corpuscles? If the answer be, in the serum, that 
solves the problem at once ; anaesthetics manifestly are agents which 
produce a profound impression directly upon nervous tissue. 
But microscopic and other examinations show that anaesthetics 
change the character of the blood-corpuscles. You are doubtless all 
of you aware of the effect of carbonic acid upon the blood. It makes 
bright arterial blood dark in color. Carbonic oxide has a directly 
contrary influence, and changes venous blood to a bright red. If 
ether be mixed with blood, it gives it a dark-purple color. It pre- 
vents its re-arterialization, and, more than this, it changes the char- 
acter of the blood-corpuscle. It dissolves it, and sets free the hem- 
atine. This phenomenon is less plainly seen in blood during its 
circulation, but it may be discerned even there. Chloroform turns 
the blood a brilliant scarlet. 
Experiment 5.—Add the vapor of chloroform, or ether, or carbonic acid, or 
carbonic oxide, to a bottle partially tilled with fresh venous or arterial blood, and 
then agitate it, when the change in color becomes apparent. To demonstrate the 
fact that ether or chloroform dissolves the blood-corpuscles, place a drop of blood 
upon a microscope slide, add to it a few drops of the fluid and place under a half- 
inch objective. Ether effects a solution much more readily than does chloro- 
form. 
We see, then, that CO and C02 are the direct antitheses of each 
other in changing the color of the blood. But this difference is not 
more marked than is that between sulphuric ether and chloroform. 
Alcohol causes blood to assume a brick-red color, and air will not 
again arterialize it. Yet the arterialization of blood is not a physio- 
logical process, but is quite mechanical. 
Experiment 6.—Procure a quantity of defibrinated blood, anaesthetize a dog, 
and open the thorax. Bleed him to death by opening the carotid arteries, or by 
severing the aorta. Quickly dissect out and sever the pulmonary vein and artery, 
and, charging a large syringe with the defibrinated blood, inject it into the artery 
until it exudes from the vein, to clear the lungs of coagulum. Remove the lungs, 
with a part of the trachea, into which insert the nozzle of a bellows. Charge 
the syringe with the defibrinated blood again, and force it through the lungs, 
when the stream will not he changed in color. Repeat this, directing an assist- 
ant to keep the lungs filled with air by means of the bellows, and it will be seen 
that the blood is now arterialized, or changed to a bright red, the same as during 
life. But if, instead of forcing air into the lungs, nitrous oxide or the vapor of 
ether or chloroform be substituted, definite modifications of the color are pro- 
duced. ANAESTHESIA. 
5 
[Note.—My observations on this experiment are not as full or com- 
plete as I hope to make them during the coming winter.] 
It is then demonstrated that anaesthetics have the power to mod- 
ify the ability of the blood-corpuscle to absorb oxygen. Is it in this 
manner that we are to account for the physiological effects of these 
agents? Let us examine some other conditions which in some of 
their phenomena resemble anaesthesia. 
During sleep, as in anaesthesia, there is primarily hyperaemia of 
the brain, as may be indisputably demonsti’ated. 
Experiment 7.—Anesthetize a healthy dog, and over one of the hemispheres 
of the brain make a crucial incision through the scalp. Dissect the flaps back, 
and trepan, using extreme caution to avoid injury to the dura mater. The flaps 
are now secured and the animal allowed to recover. After two days, to allow 
ample time for full restoration, the dura mater is exposed and the animal again 
anaesthetized. During the earlier phases, and exactly coincident with the chlo- 
roform excitement-stage of narcosis, there may be observed a distinct tumor of 
the dura mater. When anaesthesia is fully established, this is reversed, and a 
depression exists where had been the protrusion. When this phenomenon has 
been sufficiently observed, the dura mater should be carefully removed and the 
wound secured by means of the flaps of the scalp. After another interval the 
animal should be again anaesthetized, when the brain itself may be studied, and 
its periods of hyperaemia and anaemia carefully observed. 
Asphyxia presents many phases which are not unlike those of 
anaesthesia, and it is essential that we be enabled to clearly under- 
stand the difference between them. It is the result of a deprivation 
of oxygen, and its effects are mainly manifest upon the medulla. 
The lungs have nothing to do with the desire of a suffocating animal 
for breath, nor has the blood, any further than as that affects the 
medulla. 
Experiment 8.—A dog was anaesthetized and a bellows ligated in the trachea, 
so as to entirely control the supply of air. As long as the lungs were kept ex- 
panded by the bellows, it is evident that there would be no attempt at breathing 
on the part of the animal. An artery was now opened, and the dog bled so nearly 
to death that the heart almost entirely ceased acting. Notwithstanding the fact 
that the lungs were kept fully inflated, the dog now gasped for breath, because, 
from the lack of blood-corpuscles to convey it, the medulla was deprived of oxy- 
gen. A tube from the carotid artery of another previously anaesthetized dog 
was now connected with the jugular vein of the animal, and transfusion was 
accomplished, the regular lung inflations of normal breathing being kept up by 
the assistant, who worked the bellows in the trachea. When functional activity 
was fully re-established and sensation of the medulla re-awakened, the thorax 
was opened and the lungs and heart exposed. The pneumogastric nerve was 
now divided, the left ventricle of the heart opened, and at the same time the pul- 6 
ANAESTHESIA. 
monary artery ligated to cut off all blood supply to the lungs. It will be seen 
that the heart and lungs were now both isolated, or paralyzed, yet the dog gasped 
for breath. 
As long as the medulla is supplied with oxygenated blood there is 
no effort or struggle for breath, even though other organs may he 
deprived of it, but the instant that this nervous centre is left without 
its needed supply there is a convulsive effort to breathe. 
Experiment 9.—A bitch, two or three months pregnant, was anesthetized and 
the uterus opened, exposing the quarter-grown foetuses to the air. They mani- 
fested some uneasiness, hut there was no symptom of any independent existence 
so long as the circulation of the mother was kept up. But when the umbilicus 
of any foetus was severed there were shortly afterward convulsive efforts to breathe. 
This was constant with five of them. The sixth was not separated until after the 
death of the mother and the stoppage of circulation, when this foetus also made 
the same efforts for breath. 
In asphyxia the blood is dark in color, and there is the same 
anaemic condition of the cerebrum as in anaesthesia. The states of 
asphyxia and of anaesthesia] are then analogous in many character- 
istic appearances, but I shall endeavor to show that there is a wide 
difference in their pathology; for while one is but the deprivation of 
oxygen, with the consequent characteristic effects upon the medulla 
oblongata, the other has added the positive presence of a toxicologi- 
cal agent which induces an added train of symptoms. The one is 
the cessation of function in the anatomical elements, the other is but 
a partial suspension in some of them. There are the same or analo- 
gous changes in the blood-corpuscles, and yet the pathological con- 
dition is widely variant. The one is the complete absence of oxygen 
from the medulla, the other is the possible partial oxygenation in the 
tissue elements. 
Here, then, are two conditions analogous in their physical mani- 
festations, both either produced by, or attended with changes in the 
blood-corpuscles, yet the one is entirely inconsistent with continued 
functional activity, the other quite compatible with life even indefi- 
nitely prolonged. This would seem to indicate that the suspension 
of sensation attendant upon both was due to widely different causes. 
At the outset of this paper, on the authority of Snow and others, I 
spoke of carbonic acid as an aniesthetic. This was not a mere inad- 
vertence, but I did not desire to draw a distinction until it became 
plainly apparent. We now may see that, if I am correct, the two 
states are not identical. In fact, their nearest resemblance is that ANAESTHESIA. 
7 
both are conditions of insensibility; but on the same grounds a club 
may be denominated an anaesthetic, for its vigorous application will 
induce unconsciousness. We are then ready for a new definition, and 
an anaesthetic may now be denominated an agent which, existing in 
the blood in sufficient quantities, will produce insensibility to pain, 
and yet whose presence in such quantities is not incompatible with a 
continued existence. An asphyxiating agent is one which, while 
inducing entire unconsciousness, is incompatible with life. Now, as 
these two conditions are attended by the same physical symptoms, 
and are yet so widely variant, it would appear that they must be 
induced by different means. As asphyxia is demonstrably a change 
in the blood-corpuscle, it would seem that anaesthesia is due to some 
profound and specific effect produced directly by the agent itself. 
Herein the conclusions which I have reached are directly opposed 
to those of Snow, Sansom, Anstie, and most modern physiologists, 
who believe both asphyxia and anaesthesia to be due to a modified 
neural nutrition. 
Let us look at the matter from another standpoint. I have spoken 
of the changes wrought in the hue of the blood both in asphyxia and 
anaesthesia, but it is now time to say that the alterations in color are 
not due to the appearance of either oxygen, carbonic acid, or any 
other agent. The changes are induced by them, but the diversity in 
color is merely one of form. Whatever tends to distend the corpus- 
cles darkens the blood, owing to a change in its refractive powers, 
and the converse of this is also true. Thus carbonic acid distends the 
disks, carbonic oxide contracts them. Ether distends, and chloroform 
empties them, and accordingly under the influence of the former the 
blood becomes darker, while the latter makes it lighter in coloi\ It 
is thus seen that changes in hue are not necessarily indicative of 
either the presence or absence of oxygen. It does not seem reason- 
able that the profound effects of anaesthesia are produced simply by 
a change in the form of the blood-disks. It cannot well be a lack of 
oxygen, for that is simply asphyxia. We must, then, come to the con- 
clusion that the presence of the anaesthetic agent, as carried by the 
blood-corpuscle, does produce a profound impression directly upon 
nerve tissue, paralyzing it for the time, and making it incompetent 
to perform its proper functions. 
This would seem to be the case, too, when we take into considera- 
tion the manner of progression of anaesthesia, which is from the ex- 
tremities toward the central ganglions of the nerves. Anaesthetics 
also paralyze none but the sensory nerves. In both these character- 8 
ANESTHESIA. 
istics it is the direct opposite of woorari, which affects only the 
motor nerves, while its progression is from the centre toward the 
peripheries. These facts, too, seem inconsistent with the theory 
that anaesthetics produce their characteristic effects solely by the 
change in the nutrition of the anatomical elements of nerve tissue. 
Rather does it appear probable that their action is the invasion of a 
resistless enemy which, primarily attacking the outposts, where in- 
deed it is first brought in contact with the filamental tissue, in its 
onward march lays its icy hand successively upon the delicate nerves, 
and rocks them in oblivion. Just what this power is, or in what 
peculiar manner it is exerted, we know not. We can study it only 
in the phenomena which it presents. 
There are certain vegetable organisms which exhibit functions 
analogous to those of the nervous system of the animal world. The 
so-called sensitive plant presents a kind of embryonic or protoplasmic 
tissue which performs the physiological office of true nerve structure. 
It is as easily anaesthetized as an animal, and presents analogous phe- 
nomena when in an anaesthetic state. 
Another reason why it seems to me incredible that anaesthesia is 
produced through a change in nutrition, is the fact that its agents 
affect nervous force when ordinary function and blood-circulation have 
ceased. 
Experiment 10.—Remove the whole upper portion of the head of a frog, includ- 
ing cerebrum and cerebellum; open the thorax, take out the heart and lungs and cut 
off the extremities, leaving only the upper part of the alimentary canal. Two or 
three may be prepared in this way, when a smooth glass rod is thrust through each 
digestive canal, and its ends placed upon steady supports. It will now be found 
that the remaining portion of the frog will slowly travel along the glass rod, im- 
pelled by the vermicular motion of the oesophagus and intestine, and the ciliary 
motion of the larynx. But if a bell-glass he put over one of the frogs, and a 
sponge wet with chloroform be placed within it, this motion either ceases entirely 
or is materially retarded. 
Surely this cannot be from any change in the blood-corpuscles, for 
their movements have ceased. But there is a persistence of nerve 
function, especially in cold-blooded animals, which does not cease 
when other functions are lost, but which, true to its law, is suspended 
by anaesthesia. 
It seems to me unreasonable to suppose that anaesthetics should 
produce their characteristic effects through an altered nerve nutrition, 
when we remember how instantaneous is nerve action. Entire loss 
of sensation may be the result of a simple external nervous impres- ANAESTHESIA. 
9 
sion, as by fright, or shock; and this not through syncope, though an 
impression may be wrought through any of the senses which shall 
entirely suspend sensibility by means of a syncope,—itself merely the 
effect of a nervous impression. The sight of blood, the hearing of 
unwelcome news, the touch of a loathsome object, the taste of pecu- 
liarly unpleasant substances, or the memories revived through a 
penetrating odor, may instantaneously deprive a highly-wrought 
nervous organization of sensation, and induce complete syncope. 
Shall we say that these impressions ai*e produced by an altered nutri- 
tion ? It seems much more credible that they are the effect of direct 
shocks to the terminal nervous filaments themselves. 
I now believe that I have produced sufficient testimony to justify 
me in seriously questioning the correctness of the conclusions of 
Anstie, Sansom, Snow, Duroy, Lallemand, and others, that anaesthesia 
is due to an alteration in the blood-corpuscles, or to a changed nutri- 
tion. 
There are some phenomena presented in the action of the more 
common anaesthetics which are at least peculiar. While they all 
affect the sensory nerves alike, or produce the same general phenom- 
ena, their reflex effects upon the motor system and upon volition 
are widely variant. Chloroform and ether produce entire muscular 
relaxation. Nitrous oxide usually does so, but the administration of 
most of the other agents produces spasms, either tonic or clonic. At 
least this has been my own experience. Bromide of ethyl I have 
known to induce spasmodic action almost like that peculiar to strych- 
nine poisoning. 
Why is there almost an entire immunity from danger when chloro- 
form is used in parturition ? It would seem as if this agent were 
expressly intended for such occasions. There are analogous phe- 
nomena in alcoholism, as in the immunity from the effects of certain 
poisons which inebriates possess. These unusual phenomena can 
only be explained by supposing that nervous tissue is then in such 
a condition that it is no longer amenable to the profound direct im- 
pressions of the anaesthetic or toxicological agents. 
Other reasons might be advanced for the faith that is in me con- 
cerning the physiology of anaesthesia, but they would be but a re- 
hearsal of what has been better said others, and I forbear. It 
appears to me that in this direction lies a wide field for scientific 
exploration. The speculations of late physiologists have, so far as I 
am concerned, but served to befog the whole matter. What the 
character of nerve force is no man can say. It resembles electricity, 10 
ANAESTHESIA. 
but manifestly it is not that energy. That there is an impetus and 
flow to the mysterious impulse seems demonstrated, and its velocity 
has been measured, and found in man to be about two hundred and 
fifty feet per second, while in frogs it is about eighty. This rate of 
progression alone proves that it is quite distinct from electricity, even 
were it not true that there is in the nerves no such thing as a closed 
circuit, and that the mere injury to a nerve-filament stops the cur- 
rent, although there may be no solution of continuity. Neither can 
nervous force be accounted for on the hypothesis of chemical action, 
any more than by the supposition of the ancients that the nerves 
were hollow tubes through which flowed a nervous fluid. The 
whole subject is a mystery, even to the actual office of the nerves, 
for they are not essential to life, unless we except those which preside 
over involuntary muscular action, and the severing of these is only 
fatal after considerable time has elapsed. 
Experiment 11.—Anaesthetize a dog and sever both pneumogastric nerves. 
It will be found that almost immediately the breathing and the heart-pulsations 
become irregular, at first increasing in frequency, but later becoming much re- 
tarded. The animal will exist for some days, and will finally die from other 
complications than the direct stoppage of the heart through want of nerve 
impetus. 
That irritation of a nerve acts as a stimulus and sends some kind of 
an impulse along its course, we know; and that certain drugs, acting 
through other organs, produce a decided effect, either of stimulation 
or sedation, we also know. That there must exist a functional har- 
mony in the system, so that increased muscular exertion will be at 
once provocative of an increased blood supply, is an evident fact, and 
it seems to be the office of the nerves to preserve this balance. When 
we are able to comprehend the character of this nervous force we 
shall better understand the therapeutical action of anaesthetics ; and 
it seems to me that this very study of neurosis and neurotics is the 
paramount physiological and pathological question of the day. 
Anesthetics. 
The relative safety of the most commonly employed anaesthetics has 
been much discussed, and this goodly city of Boston has led the way 
in the indiscriminate denunciation of one agent as always unsafe, 
and the commendation of another as comparatively harmless. It 
must have been a model professional coroner’s jury which arrived at 
this sage conclusion. That we cannot with impunity so far interfere 
with a normal existence as to suspend some of the most important ANAESTHESIA. 
11 
functions of life must be apparent to all. But the average student 
desires to know if there are degrees in the risk to be run, and if so, 
which offers the least peril. For all practical purposes we may 
ignore all anaesthetic agents save chloroform, ether, and nitrous oxide 
gas. A long series of experiments, closely observed for the purpose 
of obtaining illumination on this point, has failed to show any definite 
reason why one agent should be always chosen to the exclusion of 
others. At one time an experiment, repeatedly tried with the same 
results, pointed to a marked difference in certain physiological effects 
upon cardiac tissue in the administration of chloroform and ether, 
and I was fondly of the opinion that we stood upon the verge of a 
grand discovery. But another series, undertaken to fortify the 
ground I was about to assume and to make assurance doubly sure, 
overthrew my inchoate theory and again impressed upon my mind 
the fact that Truth does not reveal herself hastily to the experi- 
mental novice. The record of observations was thrown away, and 
I commenced back again. 
The progression of anaesthesia is gradual. It does not overwhelm 
the whole nervous system at once, but it conquers by detail, and this 
seems to be the order of its resistless attack upon the gi’eat nervous 
centres: 
First—The cerebral hemispheres. 
Second—The spinal cord. 
Third—The general ganglionic system. 
Fourth—The respiratory ganglia. 
Each of the agents exhibits certain characteristic phenomena in 
its action, yet all follow the same general law. Certain definite 
quantities of any toxicological agent may be tolerated by the human 
economy, but that point once reached and passed, the peril com- 
mences. Were this point of danger a definitely fixed one, we might 
know when it was approached and avoid exceeding it, but the lino 
of safety depends greatly upon modifying circumstances. During 
digestion relatively large quantities of any poison may be ingested 
with impunity. A freshly-fed dog will endure a quantity of woorari 
that would be speedily fatal to one which was fasting. In producing 
narcosis we usually desire to anaesthetize the whole nervous system 
save that which presides over involuntary motion. The danger con- 
sists in going too far, and lest the point of safety be overreached, 
common prudence bids us proceed with caution. Air impregnated 
with deleterious gases may be inhaled, provided the proportion be 
not too great. Carbonic acid gas always exists in the atmosphere, 12 
ANAESTHESIA. 
and unless the proportion exceed two or three per cent, it is harm- 
less. Even as high as five or six per cent, is not specially injurious 
to the person accustomed to its inhalation, and Berzelius says that a 
man will live for some time in an atmosphere containing thirty per 
cent, of carbonic acid. Of carbonic oxide one per cent, is injurious, 
and can be inhaled for but a short time. Chlorine may be breathed 
in small quantities with impunity, notwithstanding the well-known 
acrid qualities of that gas. We see, then, that any gas may be so 
largely diluted with air as to fail to produce its toxicological effects. 
But there is a proportion beyond which we cannot go in the inhala- 
tion of any gas or vapor which will not support life. Exhaustive 
experiments have abundantly proved that not more than five per 
cent, of chloroform or ether can be breathed without extreme danger, 
and the observations of Lallemand, Perrin, and Duroy have demon- 
strated that an atmosphere of eight per cent, of chloroform is fatal, 
while two per cent, can bo breathed a long time without inducing 
the anaesthetic state. That the great danger in the administra- 
tion of any anaesthetic lies in allowing the patient to breathe an 
atmosphere too highly charged with the vapor is incontestably 
proved, and it must be accepted as a fact. I have not the time 
to enter into a further discussion of this subject, or to adduce the 
volumes of proof which are at hand, but the truth of the assertion 
is not disputed among experts in the administration of ether and 
chloroform. In the usual methods of giving these vapors a patient 
may easily be made to breathe an atmosphere of ten or even twelve 
per cent. What is the inference? These agents should never be em- 
ployed without the aid of an inhaler which may be implicitly depended 
upon to properly dilute the vapor. In the use of nitrous oxide safety 
lies in withdrawing it before narcosis shall have proceeded too 
far. 
In the use of chloroform, ether, and nitrous oxide there is a cer- 
tain train of symptoms, each following the other with considerable 
regularity, but not, in the several agents, with the same degree of 
intensity. The first stage of anaesthesia is one of hyperaesthesia and 
excitement. There is an increased flow of blood through an accel- 
erated action of the heart, and a dilatation of the capillaries, with 
contraction of the iris. This is especially marked in exhibitions of 
chloroform, and during its administration the excitement or hyper- 
aesthetic stage is sometimes very violent; and it is at this time that 
the danger is particularly imminent in cases of lesions of the heart. 
Under the stimulus of the great sympathetic, if the muscular tissue ANESTHESIA. 
13 
of the heart be weakened by fatty degeneration, or if there be marked 
diminution of its left ventricular capacity, its spasmodic struggles 
may result in an embolism when, as is usually the case, the muscular 
coats of the arteries are weakened through the irregular action of 
the heart, or that organ may itself become paralyzed through its 
extraordinary efforts to respond to the exertion demanded. Death 
then occurs either through spasm of the heart, or paralysis of the 
sympathetic nerve. The most reliable statistics show that more 
deaths occur at this stage of chloroformism than at any other, and I 
never heard of such an unfortunate termination in which the agent 
was not pushed beyond the bounds of prudence in allowing an 
atmosphere too heavily charged with the vapor. 
Another symptom attending this stage, or immediately preceding 
it, is the choking sensation, or feeling of suffocation, attended fre- 
quently with violent coughing and spasmodic struggles for air,— 
another indication that the vapor is not sufficiently diluted. These 
symptoms may arise from two causes. I have in the first part of 
this paper shown that chloroform and ether modify the ability of the 
blood-corpuscle to absorb oxygen, and if the atmosphere be too highly 
charged with the vapor of either, the medulla soon manifests its im- 
perative needs by spasmodic struggles for breath and by symptoms 
of asphyxia. The coughing arises from irritation of the terminal 
filaments of the glosso-pharyngeal nerve, as is proved by the loss of 
taste, and by the fact that if tracheotomy be performed and the vapor 
introduced through the tracheal tube, no such symptoms are ever 
observed. Any of you who have experimented with animals when 
the nozzle of a bellows was introduced into the trachea for the pur- 
pose of artificial respiration, and have anaesthetized the animal by 
means of a sponge applied to the valve, must have noticed this. 
The next physiological sign in narcosis is contraction of the arte- 
ries, due to a still more profound impression upon the vaso-motor 
system, and the beginning of the loss of sensation in the extremities, 
as indicated by a tingling feeling in the fingers and toes, which grad- 
ually extends toward the vital organs. 
If the excitement stage be once safely passed, chloroform narcosis 
proceeds quietly until the sensory nerves of the cerebro-spinal system 
are quite paralyzed, and if it be not pushed too far, the danger is very 
remote. If chloroform be properly administered and closely watched, 
it is not as dangerous as has often been represented; but its exhibi- 
tion absolutely demands the services of a skilled expert, for as it is 
more powerful than any of the other agents, it requires greater care 14 
ANESTHESIA. 
on the part of the administrator. Especially should the iris of the 
eye be closely watched, for though in its later .stages the pupil is ex- 
panded, caution must be observed that the total relaxation of coma 
be not approached. The danger is chiefly during the excitement 
stage, and then it is usually the result of want of prudence in allow- 
ing too great a proportion of the vapor. 
In ether narcosis the excitement period is seldom attended with 
such violence as with chloroform, and hence there is less danger at 
this time, for the instances in which ether has proved fatal through 
paralysis of the heart are very rare indeed, if they exist at all. In 
all cases of death from ether of which I have any knowledge, the 
heart has pulsated some time after the cessation of breathing, but 
with chloroform it is the reverse. Ether, like chloroform, first stim- 
ulates the heart, but it does not seriously depress it afterward. Tho 
great danger in the administration of this anaesthetic is from the 
arrest of respiration, and this is duo cither to a paralysis of the 
sympathetic, or more often to the filling-up of the smaller bronchi 
by mucus, through the destruction of the sensibility of the membrane 
lining them, and the consequent cessation of the ciliary motion of 
the villi, which carries the rmicus forward until expectoration can 
remove it. In nearly all cases of death from ether it will bo found 
that bronchial rales and stertorous breathing precede death, the 
latter symptom being due to paralysis of the pharynx. By the 
expert the unfavorable symptoms from chloroform may be earlier 
and more surely detected than can those from ether. 
The progress of narcosis; according to Anstie, is in its effects mani- 
fested— 
First—Upon the cerebral hemispheres. 
Second—Upon the cerebellum. 
Third—Upon the medulla oblongata. 
And the narcotized individual will lose— 
First—Local sensibility in the extremities. 
Second—The intellectual powers. 
Third—The general power of co-ordination. 
Fourth—Power of receiving sensory impressions. 
Fifth—Power of breathing. 
Sixth—Involuntary muscular action. 
There seems to be, also, a general progress of anesthesia through 
the cerebral nerves from the anterior portion of the brain posteriorly, 
for the first sense which is lost is that of smell, as is demonstrated by 
the usual demand for more of the agent, and this demonstrates a par- ANESTHESIA. 
15 
tial paralysis of the first pair of nerves. This phenomenon is readily 
accounted for by the fact that the anaesthetic reaches the terminal 
filaments of the olfactory nerves before it is presented to those of any 
other, and is an additional argument in favor of the theory that 
anaesthetic effects are produced by a direct impression upon nerve 
filaments. After the loss of smell comes loss of sight, loss of ability 
to control some of the muscles of the eye, and an enlargement of the 
pupil, owing to paralysis of the ciliary and recti muscles, which indi- 
cates the overcoming of the third, fourth, and sixth pairs of nerves. 
About this time follows loss of sensation in the integument of the 
face and eyelids, of the muscles of the tongue and of the teeth, indi- 
cating paresis of the fifth. This is followed by loss of the expression 
of the face, and of hearing, denoting a paralysis of communicating 
nerves of the seventh and of the eighth, while the tenth, eleventh, 
and twelfth pairs of cranial nerves are the last to succumb. 
Of nitrous oxide and the bromide of ethyl, time forbids me to speak 
extendedly. The first, the especial refuge of quacks, is of use only in 
brief operations, like the extraction of single teeth and the opening 
of abscesses. With the last my own experience has been anything 
but pleasing. In its administration to the lower animals, clonic 
spasms, sometimes of a very violent character, have induced too great 
a distrust of its safety to warrant me in giving it to human beings. 
There are many other things of which I would be glad to speak, and 
many experiments and vivisections which I have made, especially 
some illustrating modifications in the circulation of the blood, which 
I would desire to relate, but I spare you the recital. 
My own experiments and observations in the use of chloroform and 
ether would lead me to use especial caution, in case of the former, to 
see that there had been no indication of weakened heart’s action, as 
exhibited by fainting and d}Tspnoea; to use especial caution with those 
addicted to the use of alcohol, and to be particularly careful to give 
thorough dilution of the vapor until the excitement stage be passed. 
Finally, to carefully watch the later stages of anaesthesia, and to sus- 
pend the administration at the first indication of any excessive dila- 
tation of the pupil, of stertorous breathing, or of relaxation of the 
muscles of mastication, as these are governed by nerves which arise 
from the medulla, and indicate danger to the sympathetic system. 
In ether narcosis, instead of watching so carefully the action of the 
heart and the pulse, I pay particular attention to the respiration, and at 
the very first appearance of bronchial rales I suspend the administra- 
tion. In case of the persistence of unpleasant symptoms from chlo- 16 
ANESTHESIA. 
roform, the utmost exertion should be put forth to stimulate the 
heart to action, such as the administration of arterial stimulants, elec- 
tric currents, and nerve shocks. If the danger occurs in ether nar- 
cosis, pay little attention to the heart or pulse, but commence artifi- 
cial respiration, and persist in it until long after hope shall have 
almost fled. Several instances are on record where artificial respira- 
tion, after the methods recommended by Marshall Hall or I)r. Silves- 
ter, has resulted in recovery long after the patient had been pro- 
nounced irrecoverably dead. In both cases keep up the temperature 
by artificial heat. Many a life has been lost which might have been 
saved only for allowing the temperature to be reduced by the sub- 
sidence of functional activity. In any case, a cool head and the pos- 
session of all your faculties, with perseverance in the use of restorative 
measures, will enable you to overcome the most determinedly adverse 
symptoms, and prove you worthy to be trusted in the gravest com- 
plications.