710 NERVOUS SYSTEM. 



These important observations we have repeatedly confirmed, and we have in our pos- 

 session the encephalon of a pigeon which recovered completely after removal of about 

 two-thirds of the cerebellum, the animal first presenting marked deficiency in coordi- 

 nating power. 



Such are the phenomena observed in experiments upon the cerebellum in birds, and 

 they have been extended by Flourens and others to certain mammals, as young cats, 

 dogs, moles, mice, etc. Our own experiments, which have been very numerous during 

 the last fifteen years, are simply repetitions of those of Flourens, and the results have 

 been the same without exception. 



The only difficulties in operating upon the cerebellum arise from haemorrhage and 

 the danger of injuring the medulla oblongata. The skull is exposed by slitting up the 

 scalp, and the calvarium is removed in its posterior portion, penetrating just above the 

 upper insertion of the cervical muscles. It is well to leave a strip of bone in the median 

 line, thereby avoiding haemorrhage from the great venous sinus, although this precaution 

 is not essential. The cerebellum is thus exposed and may be removed in part or entirely, 

 by a delicate scalpel or forceps, when the characteristic phenomena just described are 

 observed. Animals operated upon in this way feel the sense of hunger and attempt to 

 eat, but, when the movements are very irregular, they are unable to take food. We 

 have frequently compared the phenomena presented after removal of the cerebellum with 

 the movements of a pigeon intoxicated by forcing down the oesophagus a little bread 

 impregnated with alcohol, and they present a striking similarity. 



In view of the remarkable uniformity in the actual results obtained by different experi- 

 menters, it is hardly necessary to cite all of the observations made upon the lower animals. 

 The phenomena observed by Flourens have been in the main confirmed by Fode"ra, 

 Bouillaud, Magendie, Wagner, Lussana, Dalton, Vulpian, Mitchell, Onimus, and many 

 others. Certain of these authors differ from Flourens in their ideas concerning the func- 

 tions of the cerebellum, while they admit the accuracy of his observations. 



We shall eliminate from the present discussion the experiments made upon animals low 

 in the scale, such as frogs and fishes (although, in some of these, the results are in accord 

 with the observations just cited upon birds and mammals), and shall confine ourselves to an 

 interpretation of the phenomena observed after extirpation of the cerebellum in animals 

 in which the muscular and nervous arrangement is like that of the human subject. The 

 results of this mutilation are as definite, distinct, and invariable, as in any experiments 

 upon living animals, and, taken by themselves, they lead inevitably to but one conclusion. 



When the greatest part or the whole of the cerebellum is removed from a bird or a 

 mammal, the animal being, before the operation, in a perfectly normal condition and no 

 other parts being injured, there are no phenomena constantly and invariably observed 

 except certain modifications of the voluntary movements. The intelligence, general and 

 special sensibility, the involuntary movements, and the simple faculty of voluntary motion, 

 remain. The movements are always exceedingly irregular and incoordinate ; the animal 

 cannot maintain its equilibrium ; and, on account of the impossibility of making regular 

 movements, it cannot feed. This want of equilibrium and of the power of coordinating 

 the muscles of the general voluntary system causes the animal to assume the most absurd 

 and remarkable postures, which, to one accustomed to these experiments, are entirely 

 characteristic. Call this want of equilibration, of coordination, of "muscular sense," an 

 indication of vertigo, or what we will, the fact remains, that regular and coordinate mus- 

 cular action in standing, walking, or flying, is impossible, although voluntary power 

 remains. It is well known that many muscular acts are more or less automatic, as in 

 standing, and, to a certain extent, in walking. These acts, as well as nearly all voluntary 

 movements, require a certain coordination of the muscles, and this, and this alone, is 

 abolished by extirpation of the cerebellum. It is true that destruction of the semicir- 

 cular canals of the internal ear produces analogous disorders of movement, but this is the 

 only mutilation, except division of the posterior white columns of the spinal cord, which 



