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SCIENCE 



[N. S. Vol. XLV. No. 1173 



that in the past few years I have been con- 

 ducting studies on the origin of that most 

 intricate and complex systems of organs, 

 the nervous system, and in fact it is to this 

 institution that I have come for a time to 

 continue such investigations. It may not be 

 inappropriate, therefore, if I attempt to tell 

 you in as simple and direct a way as I can 

 something of the problem on which I have 

 been working and of the results that I be- 

 lieve I have attained. 



Every one knows nowadays that there is 

 an intimate and important relation between 

 man's intelligence and his brain, that his 

 eyes, ears and other sense organs deliver to 

 him information concerning the exterior, 

 and that by means of his muscles controlled 

 through his nerves, he can mold his sur- 

 roundings more or less to his liking. But 

 perhaps few persons have realized how 

 strictly nervous all these operations really 

 are. Take, for instance, the apparently 

 simple question of the seat of our sensa- 

 tions. To an untrained person the pain of 

 a pin prick is located where the pin enters 

 his skin. To him nothing seems more ob- 

 vious and certain than that the punctured 

 spot is the seat of the pain and any attempt 

 to change his view on this point will usually 

 be regarded by him with suspicion and mis- 

 trust, for it seems contrary to common 

 sense. Such persons adopt more or less un- 

 consciously the opinion held by many of the 

 ancients that our sensations are spread 

 completely through our bodies, an opinion 

 which we have been obliged to give up. 

 The reasons for this change of view are sev- 

 eral. First, it has become well known that, 

 if a nerve distributed to a given area of 

 skin is cut at some distance from that area, 

 the spot, though unaffected in any direct 

 way by the operation, will give rise to no 

 further sensations even when it is severely 

 stimulated. Hence it is clear that the sen- 

 sations do not reside simply in the skin. 



But not only may pain thus be absent from 

 a given area of skin; it may be present 

 when the skin with which it is supposed to 

 be associated is absent. Persons who by 

 accident or otherwise have lost an arm or a 

 leg often experience long after the loss 

 vivid and intense sensations from definite 

 parts of the missing member. So precise 

 and sharp are these sensations and so cer- 

 tainly do they seem to be associated with 

 the lost part that some of the less knowing 

 of these unfortunates have attempted to ex- 

 hume or otherwise get possession of the lost 

 member in an endeavor to alleviate their 

 unpleasant sensations. These misunder- 

 standings, for such they are, can be swept 

 away and the matter put in its true light 

 when we recognize that our sensations are 

 not located in the peripheral parts affected 

 but in the central nervous system, and 

 within that portion of it known as the cere- 

 bral cortex. As long as this organ is in- 

 tact, sensations may arise, and, though 

 these are usually due to nervous impulses 

 from the sense organs, they may be called 

 forth by an internal stimulus as well. 

 Thus it is that a missing arm may be repre- 

 sented by sensations years after it has been 

 severed from the body. With a loss of an 

 appropriate part of the cerebral cortex, 

 however, comes a loss of sensation that is 

 absolute and final. From this there is no 

 recovery. Our sensations then are not 

 spread throughout our bodies, as was 

 taught in ancient times but are limited 

 strictly to the nervous system and in all 

 probability to that part known as the cere- 

 bral cortex. 



Not only are our sensations thus activi- 

 ties of the cortical part of the brain, but 

 there is good reason for believing that our 

 whole conscious life is similarly restricted. 

 In the cerebral cortex lies memory with its 

 wealth of stored experiences, in this organ 

 love, hate and fear come into being; here 



