942 THE CENTRAL NERVOUS SYSTEM 



nection with one of the ganglion cells that send axons to the 

 dilator muscle of the iris will, when stimulated, act as a pupillo- 

 dilator fibre, just as well as a cervical sympathetic fibre. Other 

 instances of the same law have already been given in connection 

 with the regeneration of nerves (p. 774). 



Functional union does not take place between efferent somatic 

 fibres (or pre-ganglionic fibres) and post-ganglionic fibres i.e., 

 fibres arising in peripheral ganglia, and ending in smooth muscle 

 and glandular tissue; e.g., the cervical sympathetic after excision 

 of the superior cervical ganglion does not unite with the fibres 

 leaving the anterior end of the ganglion in such a way that stimula- 

 tion of it can produce any of the effects normally produced through 

 these fibres. No proof has been given that afferent fibres can unite 

 with efferent fibres or efferent with afferent. 



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 characteristic of a primitive state has given place among the 

 most highly civilized men to extreme centralization and concentra- 

 tion. Manchester 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 pyschical 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 



