842 A MANUAL OF PHYSIOLOGY 



lectual grade. Goltz had a dog which lived more than a year 

 and a half, practically without its cerebral hemispheres, and 

 another which lived thirteen weeks. He believes that they 

 had lost understanding, reflection, and memory, but not sen- 

 sation, special or general, nor emotions and voluntary power. 

 Their condition may be best described as one of general im- 

 becility. 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 difficulties ; 

 and although everybody admits the accuracy of Goltz's descrip- 

 tion 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 irremedi- 

 able 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-sub- 

 stance, 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 func- 

 tionally 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 dbg, in addition to cutting off 

 from it a great part of its intellectual life, and is in man incom- 

 patible with life altogether. 



The results of the removal of the entire cerebral hemispheres 

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

 hierarchy. A more minute analysis shows us that the cerebral 

 cortex itself is not homogeneous in function, that certain regions 

 of it have been set aside for special labours. Our knowledge of 

 this localization of function in the cerebral cortex has been 

 derived partly from clinical, coupled with pathological observa- 



