THE CENTRAL NERVOUS SYSTEM 869 



Afferent fibres of one nerve can unite with afferent fibres of 

 another nerve, but there is not sufficient evidence to show 

 whether fibres concerned in one sensation can unite with fibres 

 concerned in another. 



The localization of function in the cerebral cortex has been 

 likened to the localization of industries in the multiplex commercial 

 life of the modern world. The barbarian household in which cloth 

 is woven and worked into garments ; sandals, or moccasins cobbled 

 together ; rough pottery baked in the kitchen fire, and all the rude 

 furniture of the lodge fashioned by the hands which built it, and 

 which rest beneath its roof at night this state of things where 

 centralization has not yet begun, it has been said, is a picture of 

 what goes on in the undeveloped brains of the frog, the pigeon, 

 and the rabbit. The ' diffusion ' of industries which is character- 

 istic of a primitive state has given place among the most highly 

 civilized men to extreme centralization and concentration. Man- 

 chester spins cotton and Liverpool ships it. Chicago handles 

 wheat and pork that have been produced on the prairies of Minnesota 

 and Illinois. Amsterdam cuts diamonds. Munich brews beer. 

 Lyons weaves silk. New York and London are centres of finance. 

 This, it is said, is the picture of the highly specialized brain of a 

 monkey or a man. But ingenious and alluring though such analogies 

 are, they do not rest upon a sufficient basis of fact. Indeed, the 

 more deeply the structure and function of the central nervous system 

 are studied, the more clearly does its essential solidarity appear, 

 the more clearly does it emerge as an organized co-ordinated system, 

 not an aggregate of separate mechanisms jumbled together for 

 convenience of storage in the protected cranio-spinal cavity. 



It has never been shown nor is it likely that the proof will soon 

 be forthcoming that there is any difference whatever in the 

 physical, chemical, or psychical processes which go on in the various 

 centres of the ' motor ' cortex. It may be supposed, indeed, that 

 the so-called sensory areas of the cortex differ more widely in their 

 internal activity from the ' motor ' areas than the latter do among 

 themselves, and that the activity of the anterior portion of the 

 brain, the portion which has been credited par excellence with 

 psychical functions, differs in kind, not merely in degree, from that 

 of all the rest. But, as we have just seen, even the ' motor ' areas 

 have sensory functions. A cast-iron physiology may explain this 

 by the assumption of ' sensory ' as well as ' motor ' cells in the 

 Rolandic area, and may find support for such an assumption in the 

 well-known fact that the large pyramidal cells whose axons form the 

 pyramidal tract make up but a small proportion of the total number 

 of pyramidal cells in this region, which, besides, contains numerous 

 cells of Golgi's second type (p. 754). Yet there is absolutely nothing 

 to contradict the supposition that the discharge of energy from 

 the most circumscribed motor area or element may be accompanied 

 not only with consciousness, but with a high degree of psychical 

 activity. And, indeed, some writers have supposed that such a con- 

 sciousness of, orjeven conscious measurement of, the discharge from 

 the ' motor ' areas is the basis of the muscular sense (Bain, Wundt). 

 So far, at least, as the ' motor ' region and the grey matter imme- 

 diately around the neural canal are concerned, the analogy of an 

 electrical switch-board connected with machines of various kinds 

 might be more correct. Touch one key or another, and an engine 



