Chap, ii.] THE BRAIN. 727 



to do, are of great value, the negative phenomena, the things 

 which the animal can no longer do, are of much less, indeed of 

 doubtful value. The more carefully and successfully the experi- 

 ments are carried out, the narrower become what we may call 

 the ' deficiency phenomena, ' the phenomena which are alone 

 and directly due to something having been taken away. Were 

 it possible to keep the rabbit alive long enough for the mere 

 effects of the operation to pass completely away, we should not 

 only probably witness, as in the case of the bird, a greater scope 

 of movement and more frequent spontaneity, but possibly find 

 a difficulty in describing the exact condition of the animal. 



§ 477. Hitherto most attempts to witness similar phenom- 

 ena in more highly organized mammals such as the dog have 

 failed; these animals do not recover from the operation of 

 removing the whole of both their hemispheres sufficiently to 

 enable us to judge whether they, like the frog, the bird and 

 the rabbit, can carry out coordinate bodily movements in the 

 absence of the hemispheres, or whether in them this part of the 

 brain, so largely developed, has usurped functions which in 

 the lower animals belong to other parts. When however in a 

 dog the cerebral hemispheres are removed not all at once but 

 piecemeal at several operations, the animal may be kept alive 

 and in good health for a long time, many months at least, even 

 after the hemispheres have been reduced to a mere fragment; 

 and it is on record that under these circumstances, the animal 

 is not only able to carry out with some limitations his ordinary 

 bodily movements, but also exhibits a spontaneity of movement 

 and a varied responsiveness to stimuli suggestive, at least, of 

 the possession of a conscious volition. If we can thus say little 

 about the condition of a dog without the cerebral hemispheres 

 we can say still less about the monkey, which in all matters 

 touching the cerebral nervous system serves as our best, indeed 

 our only guide for drawing inferences concerning man; but in 

 all probability the monkey in this respect bears somewhat the 

 same relation to the dog that the dog bears to the bird. In 

 short, the more we study the phenomena exhibited by animals 

 possessing a part only of their brain, the closer we are pushed 

 to the conclusion that no sharp line can be drawn between voli- 

 tion and the lack of volition, or between the possession and 

 absence of intelligence. Between the muscle-nerve preparation 

 at the one limit, and our conscious willing selves at the other, 

 there is a continuous gradation without a break; we cannot fix 

 on any linear barrier in the brain or in the general nervous 

 system, and say ' beyond this there is volition and intelligence 

 but up to this there is none.' 



This however is not the question with which we" are now 

 dealing. What we want to point out is that in the higher 

 animals, including at least some mammals, as in the frog, after 



