THE CENTRAL NERVOUS SYSTEM 741 



reflection, and memory, but not sensation, special or general, 

 nor emotions and voluntary power. Their condition may 

 be best described as one of general imbecility. Hunger and 

 thirst are present. They experience satisfaction when fed, 

 become angry when attacked, see a very bright light, avoid 

 obstacles, hear loud sounds, such as those produced by a 

 fog-horn, and can be awakened by them. They are not 

 completely deprived of sensations of taste and touch. But 

 it ought to be remembered that the interpretation of the 

 objective signs of sensation in animals is beset with diffi- 

 culties ; and although everybody admits the accuracy of 

 Goltz's description of what is to be seen, his interpretation 

 of the facts has been severely criticised, particularly by 

 H. Munk. 



To the monkey there can be no doubt that the loss of the 

 cerebral hemispheres would be a still heavier and more 

 irremediable blow than to the dog. But nobody has yet 

 succeeded in keeping a monkey alive after complete removal 

 of even one hemisphere. 



In man the destruction of considerable masses of brain- 

 substance, particularly if gradual, is not necessarily fatal. 

 How great a loss is compatible with life cannot be exactly 

 stated. It depends to a large extent on the position of the 

 lesion. But it is possible that one cerebral hemisphere may 

 be rendered functionally useless without immediately putting 

 a term to existence. In the foetus, however, no portion of the 

 great brain is absolutely indispensable for life and movement. 

 An anencephalous foetus (in which the brain has remained 

 undeveloped) may be born alive, and live for a short time. 



We see, then, that homologous organs are not necessarily, 

 nor indeed usually, of the same physiological value in different 

 kinds of animals. A loss which perhaps hardly narrows the 

 range of the psychical, and certainly restricts only to a slight 

 extent the physical powers of a fish, impairs in a marked 

 degree the voluntary movements of a dog, in addition to 

 cutting off from it a great part of its intellectual life, and 

 is in man incompatible with life altogether. 



The results of the removal of the entire cerebral hemi- 

 spheres help us to fix their position as a whole in the 



