1006 WITHOUT CEREBRAL HEMISPHERES. [BOOK in. 



the cry appears plaintive simply because, in consequence of the 

 completeness of the reflex nervous machinery and the absence of 

 the usual restraints, it is prolonged. 



Without insisting too much on such results as these, and 

 allowing full weight to the objection which may be urged, that in 

 some of these cases parts of the cerebral hemispheres surrounding 

 the optic thalami were left, there still remains adequate evidence 

 to shew that a mammal such as a rabbit, in the same way as 

 a frog and a bird, may in the complete or all but complete 

 absence of the cerebral hemispheres maintain a natural posture, 

 free from all signs of disturbance of equilibrium, and is able to 

 carry out with success, at all events all the usual and common 

 bodily movements. And as in the bird and frog, the evidence 

 also shews that these movements not only may be started by, but 

 in their carrying out are guided by and coordinated by afferent 

 impulses along afferent nerves, including those of the special senses. 

 But in the case of the rabbit it is even still clearer than in the case 

 of the bird that the effects of these afferent impulses are different 

 from those which result when the impulses gain access to an 

 intact brain. The movements of the animal seem guided by 

 impressions made on its retina, as well as on other sensory nerves ; 

 we may perhaps speak of the animal as the subject of sensations ; 

 but there is no satisfactory evidence that it possesses either visual 

 or other perceptions, or that the sensations which it experiences give 

 rise to ideas. Its avoidance of objects depends not so much on 

 the form of these as on their interference with light. No image, 

 whether pleasant or terrible, whether of food or of an enemy, 

 produces an effect on it, other than that of an object reflecting 

 more or less light. And we may infer that it lacks the possession 

 of an intelligent will. But it must always be remembered that 

 some of the phenomena are due to the operation producing other 

 results than the mere absence of the part removed. We must 

 bear in mind that in all the above experiments while the positive 

 phenomena, the things which the animal continues able 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 experiments 

 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. 



641. Hitherto attempts to witness similar phenomena in 

 more highly organised mammals such as the dog have failed ; these 

 animals do not recover from the operation of removing the whole 



