[Extracted from the American Journal of the Medical Sciences for April, 1869.] 
RESEARCHES 
ON THE 
PHYSIOLOGY OF THE CEREBELLUM. 
By S. WEIR MITCHELL, M.D., 
MEMBER OF THE NATIONAL ACADEMY OF SCIENCES.1 
During the last six years I have at various times engaged in studying 
the difficult subject of the physiology of the cerebellum. Like most ob- 
servers, my experiments have been made chiefly, but not altogether, upon 
birds, for the reason that these alone survive the ablation of the organ in 
question. I have gradually reached certain general conclusions as to the 
cerebellar ganglia, which differ from commonly received opinions, while as 
regards birds I shall be able to make probable a theory which in connection 
with some of my former researches must, I think, modify very considerably 
our notions in regard to the spinal and cerebellar functions of this important 
class. In order to clear the ground for the reception of my own theories 
of cerebellar activity, it will be necessary in the first place to examine 
briefly the older conceptions, a task rendered the more easy by the preva- 
lent dissatisfaction with which they are regarded by most living physiolo- 
gists. The foundation for my own opinions must rest upon experimental 
and other proofs peculiar to my personal researches, and also upon a 
wide general consideration and critical study of the clinical history of 
cerebellar disease. There are at present but two theories of cerebellar 
function which hold any place in the esteem of physiologists. The most 
popular until a few years ago was the conception which grew out of 
Flourens' researches, and which was due to that great observer. He held, 
as is well known, that the cerebellum is the sole organ in which are co-or- 
dinated the muscular movements of the body. Every year has thrown 
increasing doubt upon this view, against which he himself furnished unan- 
swerable arguments by showing that birds occasionally recover from the 
1 The conclusions of this paper were communicated to the Riol, and Mier. Dept. 
Phila Acad. Nat. Sei., Jan 18, 1869. 2 
loss of the cerebellum, and in time have restored to them the co-ordinating 
power which for a period after the operation appears to be in abeyance. 
My friend, Prof. Dalton, has been equally fortunate in saving some of the 
subjects of his ablations of the cerebellum, and in seeing them regain 
entirely the functions supposed to depend upon its existence. The birds 
similarly studied by Lussana he describes as never recovering entirely their 
ability to use the muscles with certainty, but Dr. Dalton's observations 
are too absolute to admit of doubt, and, as we shall see, he is fully sustained 
by my own experiments. Moreover it has been repeatedly shown that in 
locomotor ataxia, a spinal malady, the co-ordinating power is remarkably 
affected. It is quite needless, however, to urge further these or other argu- 
ments, and they are many, against the view of Flourens. It is enough 
that clinical experience is against it, and that after loss of the cerebellum, 
the rare survivors of the operation resume in time the function supposed 
to be forever abolished with the destruction of the ganglion in question. 
The explanation of the undoubted disturbances of muscular action, which 
are seen immediately after cerebellar ablation, will occupy us at another 
place. 
Certain modified forms of the opinion held by Flourens have been en- 
tertained from time to time by other observers. Thus Bouillaud regarded 
the cerebellum as the centre which presides over equilibration, and allotted 
to the cerebellum the co-ordination of the movements of the eyes, speech, 
and mastication, rejecting the notion which relates this organ to the in- 
stinct of propagation. The first part of his theory is more in accordance 
with facts than that of Flourens, but must be set aside upon the inexorable 
evidence afforded by the loss of the organ and the sequent symptoms. 
Serres assigned to the middle lobe the function of excitor of the genera- 
tive organs, and to the cerebellar hemispheres that of exciting motion in 
the members. 
Wagner, at the close of an elaborate memoir, concluded, 1st. That the 
cerebellum is an organ exclusively motor for the muscular apparatus of 
animal life, and probably for that of organic life. 2d. That it has an 
essential share in the co-ordination of the symmetrical movements of the 
body, and notably in those of progression, while at the same time it can- 
not be regarded simply as a regulator of motion. 3d. That it may become 
the power of departure of a direct excitation (not reflex) of certain mus- 
cular apparatuses of organic life, particularly of the abdominal viscera, 
and especially of the genital organs, and probably of the heart. The first 
conclusion as to its exclusive motor function may at present be taken for 
granted; the definition of the method of interference (co-ordination) may 
be set aside as we have shown, and the last conclusion may be left to be 
dealt with when we consider the result of irritations of the cerebellum, 
only adding that with Brown-Sequard, I am of opinion that the relations 
of-this organ to the apparatus of organic life require to be thoroughly 3 
re-examined. The last physiologist mentioned reaches as yet only negative 
conclusions, nor am I aware that he has anywhere expressed himself defi- 
nitely as regards the absolute functions of the cerebellum. Still more 
recently M. Vulpian, one of the best experimentalists of the day, has con- 
fessed, like Schiff, his inability to assign to the organ any positive func- 
tion, while he holds, with Flourens, as to the result of artificial lesions, and 
seems to consider, with Lussana, that deep lesions are never followed by 
recovery of function and perfect natural motility. 
As to the authors who have assigned sensory functions to the cerebellum, 
little need be said, since by general agreement they are held to be totally 
without support, save, perhaps, the single view advocated by Lussana and 
Dunn. These observers, especially the former, accepted the results of 
Flourens' classical experiments, but explained them by the supposition 
that the cerebellum is the ganglion of muscular sensibility. Such a view 
would be competent in explanation of the facts, but is antagonized by a 
large mass of clinical experience, and by the complete restoration of all 
motions after destruction of the organ, a fact which Lussana does not 
admit. 
Magendie seems to have had a conception of cerebellar activity which 
assigned to it an office quite trivial as regards its great size, but which had 
too long possession of the books to be passed over in silence. He re- 
garded the corpus striatum as having a backward propulsive energy, and 
the cerebellum as possessing a reverse activity, there being in health a 
physiological balance of control between the two, which was disturbed 
by the loss of either ganglion, so that the body was dominated by that 
which remained. In fact, mere puncture or irritation of the deep tissue 
of the cerebellum will often cause backward motion, the destruction of the 
organ not being essential to the production of this result. Besides which 
I have seen irritation of the medulla oblongata occasion it, and I have 
known superficial irritation of the back of the cerebellum to cause forward 
impulse, and irritation of the corpus striatum to occasion, though rarely, 
backward movement, so that Magendie's facts cannot be said to stand in 
undisputed simplicity. 
Rolando held certain views in regard to the cerebellum which accord to 
some extent with my own. He held that it was, to use his phrase, an 
" electronic teur" in which was secreted a fluid destined to provoke muscu- 
lar contraction. He adds, p. 417, that the cerebellum influences the in- 
tensity rather than the regularity of the muscular acts. I ought to add 
that as I have been unable to get his book, my quotations are at second- 
hand. Dr. J. Luys, in his excellent work on the nervous system, has given 
this view a larger development, and ably supported it chiefly by pathological 
evidence, to which I shall refer again. I do not know of any other author 
who has sustained this view by experimental arguments. I myself have 
for several years held and taught certain opinions which closely accord with 4 
those I have last mentioned, and which it is the purpose of this paper to 
develop. To avoid all possibility of misconstruction, I quote the sum- 
mary of Luy's' views with which he terminates the physiological part of 
his chapter on the cerebellum. 
" Il pent done etre comme une source d'innervation constante 
et provisoirement, comme 1'appareil dispensateur universel de cette force 
nerveuse speciale (sthenique) qui le depense en quelque point que ce soit 
de 1'economie, chaque fois qu'un effet moteur voluntaire on involuntaire 
est produit." 
From this condensed expression of his theory it will be seen that Dr. 
Luys regards the cerebellum, if I mistake not, as an apparatus for generat- 
ing nerve force to be used according to the wants of the economy in the 
production of motor power, whether voluntary or involuntary. 
The opinion which I myself entertain will be better understood at a more 
advanced stage of this essay, and I shall therefore defer its consideration. 
The experiments which I have made upon the cerebellum have extended 
over portions of at least six years. That I do not speak without a very 
large experience may be gathered from the fact, that during this time I 
have ablated the cerebellum eighty-seven times, and performed more than 
two hundred and sixty experiments upon the influence of irritants on this 
and adjoining organs. Within the last year and a half, since I introduced 
into physiological investigation the use of extreme cold, made prabticable 
by Richardson, I have added innumerable experiments to my older notes, 
and obtained results which, if not all that I could desire, are enough to 
tempt me to publish my conclusions. 
Although it has been long recognized that, in studying the influence of 
injuries upon an organ, it is necessary to bear in mind the distinction be- 
tween the phenomena due to loss of function, and those due to irritation, 
it appears to me that Brown-Sequard was the first to formularize this as 
a controlling law which should guide every physiological research. Its 
value in relation to experiments on the nervous system cannot be over- 
stated, and had it not been too much neglected, there would have been far 
less confusion in regard to the symptoms which follow injuries of the organ 
we are about to study. 
Bearing in mind the axiom above referred to, I desire, before proceeding 
further, to lay down certain rules of research, which should have a domi- 
nating influence in the present case, and which seem to me to cover the 
whole of the possibilities in the way of symptomatic phenomena. 
1. When by disease or injury an organ is removed or destroyed, the 
process of destruction may give rise to irritations which react on distant 
organs, and occasion certain symptoms. These usually subside after a time, 
but where the injury to an organ is partial, and where any diseased process 
1 Reclierches sur le Sy3t?me Nerveux. Paris, 1865, p. 429. 5 
continues, as a cicatrix, clot, or softening, they may become permanent. Ex- 
amples of this will occur to the reader too readily to require illustration. 
2. The loss of an organ may give occasion to, or permit forms of 
activity in other organs, which the healthy influence of this one controlled, 
as when the cutting off of cerebral influence allows of increased develop- 
ment of spinal reflex activities. 
3. The loss of an organ exhibits itself in some manifest defect of func- 
tion, or if after the stage of irritation is over there is manifestly no loss, 
then we are driven to the logical conclusion, either that the organ had no 
function, or else that the functional loss is provided for by a gradual in- 
crease of similar efficiency in some other organ, which alone becomes com- 
petent to the whole office, and during health must have shared with the 
lost part its peculiar duties. 
I have caused irritation of the cerebellum in pigeons, rabbits, and guinea 
pigs, by the following processes: by inserting a strong needle-like awl 
through the skull; by injuring the organ after trephining, or, in birds, 
after slicing off a piece of skull; by injecting into the cerebellum globules 
of mercury with or without a minute amount of persalts of iron to arrest 
hemorrhage; by freezing the part more or less, and allowing it to thaw 
so as to cause congestion ; and lastly, by painting the exposed part with 
tincture of cantharides or other irritant fluid. I shall pause here only to 
detail certain consequences which are either exceptional or unnoticed by 
former observers. The ordinary mechanical irritations need no special 
notice. Some of the results which follow other processes may be worth 
detailing. When in pigeons or mammals, I made a minute opening in the 
bone and injected with a syringe a globule of mercury into the centre of 
the cerebellum, it was usually followed by loss of steadiness of gait when- 
ever the injection was deeply made, but if superficial the effects were slight 
or momentary, unless either the globule was very large, or the act was 
productive of hemorrhage; in either case death often ensued rapidly. In 
one case, that of a rabbit, I lodged a minute portion of mercury in the 
right side very profoundly. It gave rise to the longest continued motwemenl 
de manege that I have ever witnessed. The animal rolled from the injured 
side, and unless guarded or supported, continued to do so during five 
weeks, when it began to acquire the power of walking without rolling, 
but was never able at any time during'four months to move forward, all 
its locomotion being at first sideways and finally sideways and forwards. 
Then paralysis of both posterior limbs took place and was speedily followed 
by death. The site of the mercury was occupied by a clot surrounded by red 
softening, and the mercury had made its way downward to the base of the 
skull, and in spite of the most careful search, could not be found. In 
another case, the globule made its way forward and was found between 
the cerebrum and cerebellum. I presume that the great weight of the 
fluid used must be taken into account in explaining these facts. 6 
I have already, in two papers, described very fully my own method of 
causing congestions by the use of Richardson's freezing spray, rhigolene 
being used in place of ether. The process has the one great objection of 
being difficult to limit, but is otherwise the only good method of causing 
profound congestion. Nothing in fact can be more perfect, as the whole 
part darkens visibly to the eye, vessels hitherto invisible appearing, and 
those which can be seen enlarging distinctly. The phenomena are pro- 
bably from the beginning irritative in character, since the congestion fol- 
lows instantly upon cessation of the spray, and goes on increasing in 
intensity as the part thaws, and the congestion spreads and becomes com- 
plete. So long as the freezing continues or is spreading, we may have 
suspension of function as complete as from ablation, but we shall hardly 
escape from some coincident irritation in the organ itself, or near ones 
at the extreme limiting edge of the chilled part. This objection applies 
alike to every mode of removing an organ or suppressing its function by 
local methods, while to none is there so little objection as to freezing, 
because as a rule the organ gradually returns to a state of health, and is 
not permanently injured. Sometimes the process employed occasions 
freezing of the medulla oblongata, when death at once occurs, as is also 
the case where for more than a moment the spinal cord is kept frozen 
in birds at any point above the dorsal vertebra. The results obtained by 
me from thus variously irritating the cerebellum or its peduncles, differ 
little from those seen by former observers. Where I have had reason to 
differ from them in opinion, I shall speak most fully, and as briefly as 
possible on points where I am at one with them. The cerebellum of the 
bird seems to me less irritable to mechanical stimulus in its outer layers 
than that of rabbits, while I believe that in the guinea pig irritations 
nearer the surface are felt most remarkably. Simple mechanical injuries, 
needle wounds, etc., are very rarely fatal in birds or the mammals named, 
and occasion no lesions of special or general sensation. Contrary to 
Bernard's statement, I have not found digestion remarkably interrupted, 
nor have I seen any permanent, intestinal troubles follow the operations. 
The motor functions alone suffer, and these are commonly re-established in 
their integrity within a period which varies from a few hours to ten days. 
As respects the form of these phenomena, consecutive to slight wounds, I 
have nothing to add to older knowledge. Superficial wounds, especially 
in birds, often occasion no visible symptom. Anteriorly and posteriorly 
deep irritations seemed to be felt as less profound ones are not, but although 
many authors have satisfied themselves that the animal then feels pain, I 
am not of opinion that this is certain. There is often a cry and a move- 
ment as the needle enters the deep posterior cerebellar regions, but apart 
from the difficulty of feeling sure that you have not disturbed the medulla, 
the movement ma/be due only to having entered a region which is an 
excitor of motion. Wounds of the deep lateral portions, involving the 7 
origins of the middle cerebellar peduncles, cause the animal to roll around 
on his long axis and occasion, as do most deep cerebellar lesions, very 
notable squints, although these are apparently wanting in birds so treated. 
Any mechanical irritation which is deep enough to give obvious effects, is 
sure to produce disturbances of motility, either tendency to move or fall 
to one side, or else general want of balance with abruptness and jerkiness 
of movement-phenomena which to my eye read as though there were a 
combination of weakness with excitation of muscles, in some cases lateral, 
in others general, but as I have said, these by degrees disappear, the rolling 
passing into a tendency to walk in a circle before perfect recovery occurs. 
The torsion of the neck and spine noted by others I have also seen. 
Quite as often in grave wounds of the posterior regions in birds there 
was a drawing backward of the head so as to produce an appearance of 
strut in the gait. 
The very singular backward movements due to certain cerebellar injuries 
have been seen by me in many cases of cerebellar wound, but are not capable 
of exact reproduction at will by this means. 
Magendie states that irritation of the medulla oblongata may also cause 
retropulsion, and Longet and others are inclined to believe that it is always 
due to some effect of the injury to the cerebellum having reached this organ. 
Flourens states that superficial lesions of the former body cause forward 
motion, and deep injuries backward impulse. I have seen both caused in 
succession by one and the same lesion of the posterior part of the cerebel- 
lum. I am not myself of opinion that the backward motions, especially 
in birds, are due to accidental injuries to the parts below the cerebellum, 
or, at least, I am sure, not only that certain irritations, such as cold 
limited to the cerebellum, are competent to this effect, but also, I am sure, 
that in rabbits this agent applied moderately to the medulla oblongata 
through the occipito-atloid space, causes only general convulsions. In 
birds also, as I have shown, a large spinal region is competent to produce 
retropulsions. The forward impulse noted above also occurs sometimes 
after the application of cold to the cerebellum ; but it is always the first 
movement, and looks like the wild effort of a confused animal at escape. 
It is promptly followed by retrogression, which has distinctly the appear- 
ance of an involuntary act, against which the animal struggles. 
Brown-Sequard refers all the phenomena of this order to incidental 
mechanical interferences with the adjacent or subjacent parts, which he 
believes competent on irritation to occasion them. This might well be, and 
yet the cerebellum itself be also directly capable of producing, when in- 
jured, the same results. 
The doubts which belong in this direction to mechanical injuries do not 
apply to congestions by the use of cold. The brain-case and skin being 
removed, a slight whiff of rhigolene, which barely freezes the superior and 
posterior cerebellar surface, causes backward motions, which cannot, I 8 
think, be referred to the parts below when we remember how difficult it is 
in birds (even by prolonged use of the spray) to freeze deeply. Such 
being the case, if we admit the correctness of this experiment, we may at 
once conceive it probable that many of the results of mechanical injuries 
have a just right to be considered as truly due to the cerebellum. Apart 
from this, I feel with Ollivier and Leven that in some of mine, as in their 
observations, it was impossible that the means-used could have mechanically 
disturbed other tissues. 
T have occasionally seen brief vomiting follow deep freezing of the 
cerebellum, but I have rarely observed it after simple wounds of this organ. 
The ocular nutritive changes described by many authors as due to cere- 
bellar injuries, I have frequently met with in rabbits and in guinea pigs, 
but never in pigeons. The change consists in slight opacity of the cornea, 
usually on the side possessing the most violent squint; whether the fixity 
of the ball of the eye in these circumstances may not possess some influ- 
ence in causing this condition, is, I think, a question of some interest. 
As regards the graver lesion, amaurosis, Wagner believes that it is 
always due in pathological human cases to pressure on near organs, as the 
tubercula quadrigemina, but as high an authority, Brown-Sequard in his 
notes on Wagner's paper, states, that he has collected sixty cases of amau- 
rosis of one or both eyes, in many of which there could have been no such 
affection of near organs. I have not seen this symptom in gnimals even 
where I have thrown foreign substances into the centre of the cerebellum 
to imitate clots, and where the animal has survived. Eleven cases lived 
after this treatment, but, although they exhibited more or less permanent 
lesions of motility and sometimes, though rarely, corneal troubles, I have 
met with no instance of loss of sight. 
Certain other troubles, which follow ablation of the cerebellum, will be 
found referred to in their proper place. 
Destruction of the cerebellum has been variously attempted, with a 
view to discover what functional deficiency follows its loss. The history 
of this portion of our subject has peculiar interest. Flourens, who 
removed the organ many times, inferred from the sequent symptoms of 
loss of equilibration that this was the co-ordinating centre, and the only 
one. In several instances, his animals recovered after loss of half the 
organ, which seems, however, to have awakened no suspicions on his part 
that his operation might have caused oidy irritative developments, which 
it was illogical to interpret as loss of function. In one case only does he 
report nearly total loss of the organ with recovery. He merely adds, 
that the cock lived more than four months and never regained his equilib- 
rium, and this is the entire history there related. 
Since then, several observers have ablated the cerebellum with intention 
to preserve alive the animal and observe the results. Longet failed in this 9 
purpose, and states that his pigeons died in three days always, and his 
mammals much sooner. 
That an experimenter so able should thus fail indicates the extreme 
difficulty of the task, in which, however, Renzi in 1858, and my friend 
Prof. Dalton, in 1867, were more fortunate. The latter kept alive four 
pigeons, which had lost large portions of the cerebellum. His last case is 
the best, because there seems to have been destruction of considerably more 
than half of this organ. There was nearly perfect co-ordination at the 
ninth day when the bird was killed. 
Wagner-1861-seems to have been ignorant of Dalton's results, and 
strangely enough of Flourens, since he states that no one has hitherto 
succeeded in preserving alive animals which have lost the cerebellum. 
Examining carefully his results, it seems that he nowhere claims to have 
succeeded in removing more than two-thirds by weight of the ganglion in 
question ; but he states that complete atrophy of the organ sometimes 
followed, which accords with Dalton's opinion, who has shown that the 
white substance below the line of incision undergoes profound textural 
alterations. In Wagner's cases there was final and complete recovery of 
co-ordinative power. Lussana-1862-also obtained recoveries, but de- 
scribes the animal as incompletely possessed of the power to direct its 
motions. The organ is said to have been annihilated. All.of these 
authors believe that, in these cases, the cerebellum was in certain instances 
thoroughly destroyed. All of them describe the immediate results as want 
of power to use the muscles usefully, loss of equilibrium, and the like. 
All of them tell us of the complete restoration of these lost powers, except 
in the case of Lussana, last quoted. Dalton distinctly affirms that there 
remained only some general feebleness, which accords with the statements 
of Ollivier and Leven, in describing grave lesions without ablation. 
With this preface, I pass to the relation of my own instances of success 
in preserving pigeons alive after removing large portions of the cerebellum. 
I have been so fortunate, at different times, as to keep alive nine pigeons, 
from which large portions of the cerebellum had been taken away. One 
of these birds is now alive in my possession. In four, which were killed 
from two weeks to two months after the ablation, there was a destruction 
of the organ which I may call complete, since, although I had removed 
only one-half in three of them, the remainder was yellow, presented but 
few nerve cells or fibres, and contained in two numerous needle-like crys- 
tals of a pale brown colour. In the fourth I took away fully two-thirds 
of the part at first. In 1866 I preserved alive one pigeon after loss of 
half the cerebellum. It recovered entirely, but died suddenly at the thirty- 
fifth day. The remnant of the cerebellum was only partially disorganized, 
a portion at the back and left side appearing healthy. In 1868, the present 
year, one pigeon lived for three weeks, surviving all loss of co-ordination, 
except a certain awkwardness in using the beak. No. 7 of my series was 10 
operated upon June 18th, and died August 4th, 1868. In this instance 
the pigeon was subject throughout to fits of convulsive gyration, alter- 
nating with stupor. Notwithstanding these, the co-ordinating power 
improved materially until a week from death, when the convulsions became 
violent and frequent. I found a large clot on and over the relic of the 
cerebellum, and much softening of the posterior cerebral tissues. The 8th 
pigeon was operated upon July 18th, 1868. I made a left lateral incision, 
removing a slice of bone, but respecting the central line, so as to preserve 
the longitudinal sinus. Fully half of the cerebellum was scooped out, and 
then with a two-edged knife I broke up a much larger portion of tissue. 
The bleeding was considerable. The usual symptoms appeared. On the 
20th the bird was better, but incapable of standing or flying. On July 
26th my assistant, Mr. Landis, took the bird to the country, and there 
carefully watched it. The remaining notes are his:- 
Arrived at Chestnut Hill July, 1868. 
July 26. In same state as on arrival-utter want of co-ordination- 
strikingly and amusingly manifest when it attempts to eat. Strikes at the 
grain of corn four or five times, missing it sometimes by several inches- 
then looks up at bystander as if ashamed of its awkwardness. Generally 
stands still with head drawn down and backwards, often making a noise 
akin to a grunt. When he moves about it is generally by a shuffling 
movemeat. 
28?A After a few grains of corn (by hand) he was let down, and 
almost immediately had several well-marked and characteristic backward 
movements. Then crouched with breast on ground fof a short time, when 
he arose and fed himself as on July 26th. From back part of wound on the 
head comes a watery fluid, showing under the microscope crystals. Was 
taken into the open air and sun for a short time, and flew a short distance. 
Is apparently strong, and his walk is improving. 
August 2. Breathing somewhat oppressed. 
1th. Walks quite well. Can fly, but does not often exercise this power. 
Is still awkward in feeding. 
13<7iand 15/A. Changed for the worse. Cause1-thermometer ranging 
from 65° to 57°. 
17/A Better. Some want of co-ordination when making violent efforts, 
as running fast, &c. 
22d. Apparently entirely well; but a slight pressure on occiput will 
cause a temporary return to former condition. Flies perfectly well. 
28th. Found dead with wound in neck-caused by cat or rats. 
No. 9 was operated upon September 8th, 1868. A left lateral incision 
was made so as to avoid wounding the cerebral sinus. The piece of skull 
was lifted, leaving it attached at one edge by soft tissues, as the lid of a 
box is by its hinges. When bleeding ceased I replaced this slice of bone, 
which became firmly fastened, so that no loss of tissue took place. Half 
of the organ was scooped out and more destroyed by the free use of the 
1 Sudden fall of temperature seemed to me very often to bring about a fatal 
result after ablation.-S. VV. M. 11 
knife, so much so that I had hardly a hope of the pigeon's*living. Vio- 
lent backward somersaults followed, and when in an hour these were 
over, there was feebleness and utter loss of power to effect any useful 
movement. Mr. Landis kindly took charge of this bird, and by great care 
succeeded in saving it. At the 18th day it was able to eat and drink, and 
could fly at the 30th day. At this date, January 15, 1869, it is in no 
respect different from its fellows, except that when pursued about the room 
it gives out sooner than others, and often quite suddenly, a symptom 
which exists in many of these cases, but which has a more peculiar value 
the further off in time it is seen from the date of operation. The latest 
sign of awkwardness was in a certain want of power to direct its beak. 
This Lussana also describes ; and it is the slight and almost the only 
ground for his decision, that inco-ordination is permanent after ablation. 
It is possible that this difficulty may be due to a relic of the early motor 
troubles which affect the neck with some form of spasm, and which were re- 
markably conspicuous in the present case. 
pefore speaking more fully of the symptoms which follow ablations, it 
will be fitting to say something as to the precautions needed to insure even 
a rare and occasional success. As it has been objected by Schiff and 
others that the cerebral circulation must be greatly damaged by removing 
the cerebellum, I have, in some cases, made only a lateral or bilateral inci- 
sion, slicing off the skull with a knife, and leaving a central bridge of bone, 
beneath which lay undisturbed the long sinus. In operating on the middle 
line, it is impossible to avoid dividing this vessel; so that death from hemor- 
rhage is common. I have tried to avoid this result by the use of little clamps, 
actual cautery, etc., but have rarely succeeded. Practically, the pigeons which 
survived this method of attack presented no features of essential difference 
from those otherwise treated, so that in this matter the theoretical objec- 
tion has no value. As convulsions of some kind always ensue, death from 
exhaustion is the next danger. This is avoided by swathing the bird in a 
bandage until able to stand, or until the fits are over. These are renewed 
very often by anything which causes sudden motion or struggle-as a loud 
noise, or the act of feeding artificially. It is best to operate when the bird 
has been lightly fed ; and, of course, for some time the subsequent nourish- 
ment must be given grain by grain with the hand. As to this there is no 
trouble, since the power to swallow is undisturbed. Even on the first day 
the bird will usually drink of itself if the beak be put in water. 
In Cases 8th and 9th I merely lifted the flap of bone, leaving it attached 
at one edge. When bleeding ceased, I replaced it, drawing over it the 
skin. Perfect union followed without loss of tissue. Usually no attention 
was paid to the wounds, which closed by membrane. 
Consequences of Ablation.-Those which are immediate have been so 
well and so often described by abler pens than mine, that I shall be as brief 
as possible. Always, if the wound be a deep one, there are convulsions 12 
which have a character of lateral or backward activity. With these, which 
soon intermit, we have a confusion of movement which is quite indescriba- 
ble, and lasts much longer. It has usually been described by authors as a 
pure ataxy, without loss of power-a wrant of ability to group together 
the various sets of muscles so as to effect distinct actions like walking or 
flying. The animal staggers, falls this way and that, beats the air fruit- 
lessly with its wings, lifts one leg or the other, and, in a word, exhibits 
what is truly described as an apparent want of co-ordination.1 This is 
one way of reading the phenomena before us. There is, I think, yet 
another. If we conceive, as we have every right of evidence to do, that 
the cerebellum is in some kind of relation with nearly all the voluntary 
muscles of the body, we can see how an irritation which embraces in one 
plane all of the nerve fibres may give rise to irregular muscular motions, 
whose persistence will be limited only by the length of time during which 
the irritation continues. It is clear that nothing is more likely than that 
we shall have elicited a confusion of muscular replies, which, for a time, 
will interfere absolutely with the usually dominating influence of the voli- 
tional centres. 
Ablation of the cerebellum is therefore equivalent, for a time, to exten- 
sive irritation of the organ, so that we have a graver reproduction of the 
symptoms which follow mechanical injuries, and which are severe in pro- 
portion as we incise the deeper parts of the organ. As we recede from the 
time of the operation these evidences of irritant action subside, until they 
are reduced to a minimum, or disappear altogether in the rare cases which 
survive the primary results of so terrible a traumatic lesion. ■ 
It is worthy of notice that during recovery the disorders due to irrita- 
tion are often reproducible by noises, alarm, or rough handling-by any 
cause, in a word, which gives rise to abrupt movements or excited circula- 
tion. Under such circumstances the pigeon has some disorder of move- 
ment for a few moments, or at the beginning of a train of movements. 
Presently, however, this subsides, and the co-ordination is perfect again. 
The only permanent change which I have seen in pigeons is one, as to 
which I am personally quite confident, but which does not admit of abso- 
lute demonstration. All of the birds which have survived a long time 
seemed to me to be incapable of as prolonged exertion as their uninjured 
fellows, and to become tired far more readily. This point has more im- 
1 Flourens has noticed the likeness between alcoholic toxication and cerebellar 
loss. In the early stages of drunkenness in birds, there is, he says, a perfect con- 
cord of symptoms with those seen immediately after ablation of the cerebellum; 
whence he concludes that alcohol acts on this organ, but finally affects the gan- 
glia of sensation and intellectuation. (Rich. Erp. sur le Syst. Nerv., p. 401.) 
It is, perhaps, hardly worth while to add, that I have found alcohol to cause in 
birds deprived of half or more of the cerebellum exactly the same symptoms as it 
does in uninjured birds. 13 
portance than it would seem at first to have, as it bears somewhat upon 
the ideas which I shall develop as to the function of the normal cere 
bellum. 
Some of the symptoms which follow ablation may be considered here. 
Vomiting is not rare, but I have not seen it later than the second day, 
and it is curious to note that it followed only one case of those which out- 
lived the operation a week. This fact alone would incline me to suspect 
that it is always due, when it does occur, to injury of the sub-cerebellar 
regions. I have already mentioned that digestion does not seem to suffer 
in lesser irritation of the cerebellum; neither does it remarkably, I may 
add, after ablation of that organ. Corn placed in the crop leaves it in 
the usual time, and the birds emaciate less than would seem probable, con- 
sidering the primary loss of blood, the confinement, and the artificial feed- 
ing. None of these, however, account fully, to my mind, for the singular 
diarrhoea which follows ablation, and persists for a week or two. 
If we admit the constant interference of the cerebellum in the motor 
activity of the muscular fibre of organic life, we may conclude that the 
diarrhoea is due to a succession of irritations affecting the motor tissues of 
the alimentary canal; but it should also be remembered that both Wagner 
and the author have seen loose evacuations as a result of cerebral abla- 
tions. Moreover, it is not yet clear whether the watery discharges in 
question owe their character to alteration of the intestinal or the renal 
excretions, both being discharged from a common cloaca. 
The negative signs which follow recovery are also of interest; excepting 
some want of power to prolong exertion, there is left no locomotor defect. 
In the region of sensation no alteration may be perceived, and in the 
sphere of emotional activities I have been unable to detect any change, as 
the pigeons bill and coo, and do fierce battle like their healthy fellows. 
The question as to the influence of the cerebellum upon the generative 
organs has been pretty fully answered in a negative direction. I have no 
new facts to tfdd to those of Wagner, Flourens, and Lussana. 
The relation of the cerebellum to the generative organs is naturally con- 
nected with an influence which many suppose it to have over reflex move- 
ments, and especially over those which belong to the muscles of organic 
life. Brown-Sequard thinks, very properly, that it is necessary in this 
matter to repeat these experiments, attentive to the fact that impeded 
respiration, as he has shown, is apt to give rise to vigorous motions in 
the intestines, womb, etc. Now, in pigeons, such researches will be likely 
to have this element of doubt thrown in, because it is very difficult to open 
the belly without injury to the air-sacs, and consequent defect of aeration. 
Even in rabbits or guinea pigs, large opening of the abdomen disturbs 
breathing by taking away from the diaphragm some of the normal elastic 
pressure of the intestines, which aids the upward movements, so that, 
although it seems easy to expose the intestines, etc., and then irritating 14 
the cerebellum to see if they move, it is by no means always possible to 
affirm that the sequent motion was truly a muscular reply to the cerebellar 
injury, and to this alone. 
Bouillaud and others have assured themselves that many at least of the 
partly reflex acts are undisturbed. To these belong deglutition and respi- 
ration, the influence of the loss of the cerebellum upon the circulation 
being still in doubt. 
I have reserved to this time a review of the very important results ob- 
tained by the application of intense cold with Richardson's spray pro- 
ducer. At the risk of being tedious I shall venture to recapitulate the 
conclusions of my former papers, and the modifications which they have 
undergone. 
During the spring and summer of 1867 I discovered that when the spine 
of birds (pigeons) is chilled anywhere above the dorsal vertebrae certain 
results follow; if the freezing be perfect and prolonged so as to act through 
the spine, death from asphyxia occurs just as if the spine were divided. 
This is due to the fact that the respiratory nerves come off all through 
this region, and is in accordance with older knowledge. Slight freezing 
causes gasping respiration, and great confusion of general motion, a hur- 
ried rush forward, sometimes general convulsions, with violent backward 
somersaults, and finally spells of curious retropulsion, alternating with 
stupors, and like all the former symptoms, less violeht after chill of the 
lower cervical vertebrae than from like injury of the upper region. The 
experiments vary a good deal, but in many the wild confusion of move- 
ment and the loss of equilibrium with the apparent retention of a large 
share of usual power, all brought to my mind the cerebellar lesions 1 had 
so often seen followed by like phenomena. I also found that freezing of 
the cerebellum gave me precisely the same effects. I next discovered that 
direct irritation of the cervical spinal cord with irritants (capsicum) occa- 
sioned the backward spells after some hours, and the influence of the irri- 
tants proved more permanent than that of cold. At first I hoped to 
destroy for a time by freezing the influence of the cerebellar ganglion, but- it 
is now clear to me that all the phenomena of action are due to the congestion 
which cold secondarily occasions, for it is impossible accurately to preserve 
the limits of the freezing, and so in the cerebellum we shall have a plane of 
varying congestion at the far line of the congelation. Also both here and 
in the spine, the motor phenomena are often delayed for a minute or more 
and then go on increasing in severity for a time. All of this is explicable 
if we comprehend that even while the freezing lasts there is probably a 
plane of irritation at the edge, that this speedily widens when we stop the 
spray, and that it quickly pursues the retiring line of cold as the re-es- 
tablished circulation passes by degrees into a congestion so profound as 
often to cause minute apoplectic effusions. Very little, then, of the convul- 
sive acts is due to the direct effect of cold, much more to the intense and 15 
overpowering congestion which in turn wears off. The added proof lies 
in the fact that local irritants which congest more slowly, occasion in the 
spine the same phenomena after the lapse of a longer interval. 
In the following summer I made the more curious discovery, that cold 
applied suddenly to definite tracts of skin in pigeons gave rise to precisely 
the same retrogressive movements as if I had frozen the correspondent 
spinal regions. More strange still, when I froze the left or right side of 
the crop, the pigeon walked to the side opposite to that frozen. All of 
these movements followed the freezing at intervals as long as five to ten 
minutes, and sometimes failed altogether. Here, then, was a resemblance 
to the facts of cerebellar lesions which was certainly calculated to startle 
the modern physiologist. I should perhaps state at this point that all of 
the phenomena in question have been verified by Dr. Richardson and 
others. 
Up to the last summer, that of 1868, the only time of the year when 
my daily business permits me to pursue physiology, I had referred all of 
the curious co-ordinated spasms, as well as the other appearances of loss 
of equilibrium, convulsions, etc., to the cerebellum. In June and July, 
however, I took up anew the question of cerebellar functions, and dis- 
covered to my surprise that after my pigeons had lost part or the whole 
of the cerebellum and recovered, they were still capable of exhibiting in 
perfection the retrogressive acts, backward convulsions, and lateral walking. 
Other irritants applied to the spine gave also the usual results, so that it 
became clear that I had been mistaken, and that the cerebellum was not 
needed to produce the phenomena I have described. 
I made many efforts to irritate the lateral columns of the spine to cause 
lateral motion, but always failed to attain my purpose. If I could have 
kept alive a pigeon after dividing the spine in the neck, and then have 
frozen the portion below the section, I might have been successful in 
proving absolutely the independent possession by the spine of certain cere- 
bellar properties. I endeavored to do this by keeping up artificial breath- 
ing after such sections, but was defeated by various obstacles which will 
occur to every biologist. 
There is another fact which lies in the same direction as many of my 
own, and is of great interest in this connection. Brown-Sequard relates 
that when in the lumbar enlargement of the spinal cord of birds, he ex- 
posed to the air the gray matter which there lies externally, a curious dis- 
turbance of movement immediately followed, and was not observed else- 
where in the spine, at parts whose white neurine alone lies outside accord- 
ing to the common arrangement. The disturbance, he says, "very* much 
resembles the so-called titubation, which exists after either the removal of 
the cerebellum, or the section of muscles of the posterior part of the neck." 
As I have shown, however, deep freezing higher up occasions the most 16 
profound confusion of motion, because the congestion in this case reaches 
the gray matter easily. 
In the light of all that I have previously pointed out, I shall now review 
the question of cerebellar function. 
We must admit, in the first place, that apparent loss of co-ordination 
follows cerebellar lesions. It appears clear from my own researches, that 
these injuries do not cause this result, owing to mechanical and incidental 
affections of near parts. 
In birds, injuries and congestion of the spine give rise, at first, to seem- 
ing in-coordination, or at least to exactly such phenomena as follow like 
injuries addressed to the cerebellum. When the cerebellum has been 
removed spinal irritation still continues to evolve the same symptoms as 
when the cerebellum exists untouched. These facts indicate for these two 
organs in birds at least, a curious community of pathological symptoms 
and probably of physiological function. If then there be such a functional 
entity having a separate seat as the so-called co-ordination, it belongs in 
birds to an extensive region, including the cerebellum and a large part of 
the spine. 
There is yet possible, however, another view of cerebellar activity which 
will accept all of the facts and account for all. Let us suppose the cere- 
bellum to be a great ganglionic mass, possessing the same motor functions 
as the gray matter of the spine, related like it, and through it, to the 
voluntary muscles. Irritations of its tissue, ablation, the temporary equiva- 
lent of extensive irritation, congestions, as from cold or other causes, might 
occasion both directly through the spine, or indirectly by reaction on its 
ganglia, just such confusion of motion, restlessness, and locomotor disor- 
ders, as we do actually see and as were said entitle it to be called the organ 
for co-ordinating muscular acts. As the irritation disappeared, so would 
the muscular disturbances, until, when there was no longer irritation, there 
would cease to be locomotor difficulties of the character described, the spinal 
centres having by degrees assumed with the aid of the will the function 
shared in health with the lost organ. 
Referring anew to laws of research laid down at a former page, I remind 
the reader, that if an organ be lost, and no function finally disappears, it 
either had none or possessed one in common with some part which remains 
uninjured and capable of at last supplementing the function of the 
destroyed tissues. For these reasons I am disposed to deny to the cerebel- 
lum any larger share in co-ordination than exists in any ganglion employed 
in voluntary motion, and to assign to it a part closely relating it in powers 
to the chain of spinal ganglia. The cerebellum becomes for me, therefore, 
a great reinforcing organ, capable of being more or less used in volitional 
muscular motion. Its loss, as I have elsewhere stated, leaves finally no 
functional defect save some incapacity for prolonged motor activity. 
The apparent in-cobrdination which follows section through the deeper 17 
layers of the cerebellum, is simply a confusion of movement due to the 
joint action of two separate and interfering agencies. In health the cere- 
bellum is called upon by the will when needed, and acts through the spine 
on the muscles. After irritation or ablation (the equivalent, for a time, 
of extensive irritation), we have two sets of forces in action-that arising 
from the excited and wounded efferent cerebellar fibres, a force inconstant, 
irregular, involuntary; and secondly, the normal activity of the will, which, 
in presence of the former disturbing power, fails to evolve the usual orderly 
reply from the muscles. The general result is seen in the strange confu- 
sion of movement which is so familiar to the physiologist. 
I am very far from supposing that what I have here urged as experi- 
ment or argument is at all complete. I am well aware that much may be 
said against my views, and perhaps something more in their support. It is 
clear, however, that as yet we have had no cerebellar theory supported by 
any weight of experimentation. The theory which I have here set forth 
may or may not be correct, but it seems to me to have more in its favour 
than any other yet advanced. Should it meet with no success, it will still be 
impossible to frame any consistent hypothesis of cerebellar activity which 
does not account for the new facts in this connection which I have pub- 
lished ; so that if these have been well and honestly observed and stated, 
I shall not have laboured altogether in vain. 
I ought to add, that while I believe the cerebellum to be one of the 
great centres of force-development for voluntary, and perhaps involuntary 
motion, I am not at all prepared to assume that it has no other function. 
Whatever quarrel may be made with this argument as regards mammals, 
it seems to me quite clear that, in birds, a relationship of function with 
that of the spine is fairly made out, even if we hold to the older views of 
the co-ordinative powers of the cerebellum, a doctrine which I am quite 
indisposed to admit. While in birds, then, there is great reason to induce 
us to accept the view previously stated, and which would teach us to look 
upon the cerebellum as a great additional centre of motor power, called 
into habitual activity by the will, and co-operating with the spinal ganglia, 
there is nothing in experiments upon the cerebellum of mammals to con- 
tradict such a theory. Irritations of the cerebellum in this class occasion 
exactly the same kind of motor disturbances and irregularities as in birds. 
Ablation productive in mammals of primary symptoms in nowise unlike 
those of birds, ceases here to offer us further proof, because, as yet, no one 
has succeeded in saving the life of a mammal deprived of the cerebellum. 
I ought also to add, that I have found it impossible to cause by cold ad- 
dressed to the spine of mammals those phenomena which are seen in birds 
upon so disturbing either the spine or cerebellum. For this reason many will 
perhaps hesitate to admit in mammals that community of spinal and cere- 
bellar functions which I have made at least not improbable in the class of 
birds. Nor would there be anything to shock us in such an admission, 18 
because in the lower animals many functions are disseminated over large 
regions which in higher creatures are centralized, so to speak. This is 
well enough illustrated in the frog, which, after decapitation, executes 
many and complicated reflex acts with entire co-ordination, despite the 
absence of brain. There is therefore no doubt that the reptile class pos- 
sesses, in a larger degree in the spinal regions, motor powers, which in 
higher classes exhibit themselves only under the influence of intra-cranial 
ganglia. The physiological gap between birds and their next higher 
neighbours in the ascending scale of life is a very wide one, so that if that 
were in a measure true of birds which proved not to be of mammals, it 
need excite no great surprise. I mentioned, early in this paper, that com- 
parative anatomy gave us little aid in determining the cerebellar offices. 
On the other hand, comparative experiments upon animals below the class 
of birds, seem to afford important additions to the evidence already offered 
that the cerebellum is principally a motor ganglion supplementing the 
group of spinal nerve cells, and like them dominated by volition. I found 
it needless to experiment as to the cerebellum in frogs, fish, etc., since this 
had been already fully done. Thus, as Vulpian points out in frogs and 
fish, removal of the cerebellum alone produces no noticeable symptom, un- 
less the peduncles have been injured. In these classes the organ is rela- 
tively small, and we may presume, if for a moment we accept my views, 
that the spine is largely predominant in the* ordinary product of motor 
power, so that ablation of the cerebellum causes in these animals less than 
any that disturbance of movement which comes from irritating a vast 
number of motorial fibres. 
It was at one time ray intention to examine how far the pathological 
evidence in man would sustain the view of cerebellar function which I 
have, with many doubts, brought forward in the absence of any one more 
probable. After studying with critical care a large number of cases of 
cerebellar lesions, I found that very few of them could properly be used, 
owing to there having been no microscopical inspection of near organs. 
We have numerous symptoms, some of which at least we cannot reproduce 
by artificial injuries. They may be the legitimate offspring of the cere- 
bellar disorder, but since they may also be due to affections of the medulla 
oblongata or optic ganglia, etc., we have no right to feel sure that these 
latter organs are not the true parents, unless they have been examined by 
every possible means. On the other hand, while many of the phenomena 
of disease are also seen in some modified shape in the laboratory, it is well 
to remember that, nearly always, disease acts slowly, giving us rarely 
those trenchant results which follow the abrupt interferences of the phy- 
siologist's scalpel. I may say, in conclusion, that after analyzing an hun- 
dred cases, Luys tells us that progressive muscular feebleness was noted in 
forty-five. I myself have reached nearly the same result from the study 
of cases other than his, and I feel at least authorized to say, that while 19 
for reasons above stated the cerebellar pathological evidence is inconclu- 
sive, it is more in favour of the views I have set forth than of any of the 
precedent theories. 
In conclusion, I desire to express my warmest thanks to my assistant, 
Mr. Landis, without whose ingenuity and care I certainly should not have 
been able to preserve alive any of the recent subjects of attempts at cere- 
bellar ablation.