69 8 NERVOUS SYSTEM. 



experimental conditions necessary for determining this point are the following : The 

 observer must be certain that the removal of the hemispheres has been complete ; for it 

 has been clearly shown that, even when a small amount of cerebral substance has es- 

 caped, the functions of these parts are not entirely abolished. Again, we must be equally 

 certain that movements which seem to be due to a spontaneous act of volition take place 

 when the animal has not been aroused from the condition of stupor which results from 

 the operation. Generally, when the animal is left to itself, the condition of stupor per- 

 sists ; but, when aroused by artificial means, it will walk a few steps, plume the feathers, 

 shake its head, and make various voluntary movements without farther irritation, soon 

 relapsing, however, into somnolency. One of the most accurate and reliable of the 

 recent observers of these phenomena, Vulpian, asserts without reserve, that an animal, 

 deprived completely of the cerebral hemispheres, is incapable of a spontaneous voluntary 

 eifort ; and we are inclined to an unqualified adoption of this opinion. "With regard to a 

 rabbit from which Vulpian had removed the cerebral hemispheres and the corpora stri- 

 ata, he makes the following statement : " I do not hesitate to say that this rabbit is 

 completely deprived of spontaneous volition. All its movements, which are, indeed, 

 much less varied than those of a bird operated upon in the same manner, are exclusively 

 and directly due to a stimulation produced by exterior excitations, or by interior inclina- 

 tions, such as fatigue, etc." 



In view of the very great variety of movements that occur in animals after removal 

 of the cerebrum, it is quite difficult to define precisely what movements are due to volun- 

 tary action depending upon some external or interior impression, which are really reflex 

 voluntary movements, and to distinguish them from those which arise from a spontaneous 

 and, perhaps, an intelligent effort of the will. These points have been so admirably 

 described in a recent article, by Onimus, that we quote his concluding summary : 



" As a summary, in the inferior animals, as in the superior animals, the removal of the 

 cerebral hemispheres does not cause to disappear any of the movements that previously 

 existed. Only, these movements assume certain peculiar characters. In the first place, 

 they are more regular, they have the true normal type, for no psychical influence inter- 

 venes to modify them ; the locomotor apparatus is brought into action without interfer- 

 ences, and one could almost say that the ensemble of movements is then more normal 

 than in the normal condition. 



" In the second place, the movements executed take place inevitably after certain 

 excitations. It is a necessity that the frog placed in water should swim, and that the 

 pigeon thrown into the air should fly. The physiologist can then, at will, in an animal 

 without the brain, determine such and such an act, limit it, arrest it ; he can anticipate 

 the movements and affirm in advance that they will take place under certain conditions, 

 absolutely as the chemist knows in advance the reactions that he will obtain in mixing 

 certain bodies. 



"Another peculiarity in the movements that take place, when the cerebral lobes are 

 removed, is their continuation after a first impression. On the ground, a frog without 

 the brain when irritated makes, in general, two or three jumps at the most ; it is rare 

 that it makes but one. Placed in water, it continues the movement of natation until it 

 meets with an obstacle ; it is the same in the carp, eel, etc. The pigeon continues to 

 fly, the duck and goose continue to swim, etc. We should say that there is a spring 

 which needs for its action a first impulsion, and which is stopped by the slightest resist- 

 ance. But, what is striking, is precisely that continuation of the condition once deter- 

 mined, and we cannot refrain from connecting the facts observed in an animal deprived 

 of the cerebral lobes with those which constitute the characteristic properties of inor- 

 ganic matter. Brought into movement, the animal without a brain retains the move- 

 ment until there is exhaustion of the conditions of movement, or until it meets with 

 resistance ; taken in repose, it remains in the state of inertia until an exterior cause 

 intervenes to bring it out of this condition. It is living, inert matter." 



