EXTIRPATION OF THE CEEEBBUM. 333 



conditions, would excite terror and an idea of danger, simply 

 causes the pigeon to give evidence that the sound has been 

 heard. As we have already stated, it is probable that the 

 animal has the sense of smell, but it is difficult, if not im- 

 possible, to establish this point experimentally. The same 

 remark applies to the sensations of hunger and thirst. The 

 animal may feel the want of water and food, but, it has no 

 idea of relieving these sensations by drinking and eating, 

 and, if left to itself, will die of inanition. 



There has been a great deal of discussion among experi- 

 mentalists with regard to spontaneous voluntary movements 

 in animals deprived of the cerebral hemispheres. The ex- 

 perimental 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 cere- 

 bral substance has escaped, the functions of these lobes 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 opera- 

 tion. Generally, when the animal is left to itself, the con- 

 dition of stupor persists ; but when aroused by artificial 

 means, it will walk a few steps, plume the feathers, shake 

 its head, and make various voluntary movements without 

 further irritation, soon relapsing, however, into somnolency. 

 One of the most accurate and reliable of the recent observ- 

 ers of these phenomena, Yulpian, asserts without reserve, 

 that an animal, deprived completely of the cerebral hemi- 

 spheres, is incapable of a spontaneous voluntary effort ; and 

 we are inclined to an unqualified adoption of this opinion. 

 "With regard to a rabbit, from which Yulpian had removed 

 the cerebral hemispheres and the corpora striata, 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 



