622 THE HUMAN BODY. 



it may be said in general that the systems of fibres represented 

 in Fig. 177 are all almost certainly concerned in conveying 

 impulses from the cortex, and those in Fig. 178 in the trans- 

 mission of afferent impulses. It will be noted that both affer- 

 ent and efferent fibres are abundant in the internal capsule ; 

 and that the corpus striatum and pes are more especially con- 

 nected with efferent and the tegmentum and thalamus with 

 afferent impulses. It can hardly be necessary to add that 

 each line in the diagrams represents hundreds of thousands 

 of nerve-fibres. 



The Functions of the Cerebral Cortex. That this part of 

 the nervous system is in close association with the intellect and 

 with the initiation of voluntary movements seems beyond 

 doubt: but it may have other functions quite apart from any 

 states of consciousness ; and intelligence and every volition may 

 not entirely depend on it. The experiments made in recent 

 years on the lower animals tend to the conclusion that some 

 will and some intellect may remain in animals all or almost all 

 of whose gray cerebral surfaces have been removed ; the more 

 complete loss of those powers described by earlier workers 

 being due to the fact that the animals were not kept alive long 

 enough after the operation. It has been observed that a dog 

 whose cerebral cortex (as verified by subsequent post-mortem 

 examination) had been nearly completely removed did learn 

 after some months to walk about to all appearance voluntarily, 

 and to find and eat his food ; he even learned not to take the 

 food of other dogs after he had been severely bitten several 

 times for so doing. But more complex perceptions were lost : 

 before the operation, for example, he was greatly terrified by 

 seeing a man fantastically dressed, but afterwards no such 

 appearance aroused in him so complex a conception as that of 

 a strange or dangerous object. He also never recovered the 

 trick of "giving paw," which had previously been taught 

 him. But on the whole a person casually observing him would 

 not have thought him very different from any other dog, ex- 

 cept perhaps that he was rather stupid : put into a low open 

 box, for example, he would not jump out of it when called, 

 though he easily could do so and clearly desired to. Such 

 simple and fundamental perceptions and volitions as remained 

 in this and some similar cases probably have their seats in the 

 optic thalami and corpora striata, and indeed embryology shows 

 that the corpora striatum is morphologically a part of the 



