410 THE AMERICAN NATURALIST [Vol. XLII 



neural processes would consist in the activity, in turn, of 

 visual sense organs, neurones conveying the visual im- 

 pressions to the brain, cerebral neurones mediating the 

 sensation and perception of the terrifying car, motor 

 neurones controlling the peripheral muscular actions 

 that are involved in the organic processes, neurones con- 

 veying to the brain the impressions of altered heart beat, 

 constricted arteries and trembling muscles, and lastly 

 cerebral neurones mediating the feeling of fear. Because 

 of its difficulty, much of the work of geographical explora- 

 tion within the central nervous system is at present neces- 

 sarily inexact, and moreover there is still much terra 

 incognita. And even though we have thus come to know 

 the gross functions of specific parts of the higher mam- 

 malian and human brains, we still know all too little of 

 the processes by which the different parts are coordinated 

 and made to subserve the many complex needs of the 

 organism. The recent work of Professor Sherrington on 

 the integrative action of the nervous system is an 

 admirable example of the kind of investigation that is 

 needed in this field, and by its very excellence helps to 

 emphasize the lack of our knowledge. The laboratories 

 of physiological psychology, now numerous, are making 

 many valuable contributions, especially to our knowledge 

 of the mechanism of the special senses. But when I make 

 a summary of what we now know of the physiology of the 

 nervous system, I come to realize anew its paucity, com- 

 pared with what we ought to know and shall know, I am 

 confident, in the long future. Here, it seems to me, is a 

 field sadly needing tillage, and one where, though tillage 

 be extremely difficult, the yield is certain to be rich. 



All investigation here will lead up, in a sense, to the 

 solving of that problem of problems, which has been for 

 ages the focus of discussion and speculation, the problem 

 of consciousness— 4 4 at once the oldest problem of phi- 

 losophy and one of the youngest problems of science." 

 For centuries it has been thought about, talked about, 

 written about, and with what result? The elaboration of 



