978 THE CENTRAL NERVOUS SYSTEM 



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 

 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. 856). And although it may be true that the 

 tactile sensations constituting the so-called body-sense are represented 

 mainly not in the motor region itself, but in the adjacent gyrus post- 

 centralis posterior, to the Rolandic fissure (p. 951), there is nothing to 

 contradict the supposition that the discharge of energy from the most 

 circumscribed motor area or element may be accompanied with con- 

 sciousness. And, indeed, some writers have supposed that such a 

 consciousness of, or even 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 is set in 

 motion to grind corn, or to saw wood, or to light a town. The difference 

 in result lies not in any difference of material or workmanship in the 

 switches, but solely in the difference in their connections. 



Grey matter in the upper part of the precentral convolution is excited, 

 and the muscles of the leg contract. Grey matter on the lower part of 

 the convolution is excited, and there are movements of the face and 

 mouth. Grey matter in the medulla oblongata is excited, and the 

 salivary glands pour forth a thin, watery fluid, poor in proteins, and 

 containing an amylolytic ferment. Another portion of grey (?) matter 

 in the medulla is thrown into activity, and the pancreatic ducts 

 become flushed with a thicker secretion, relatively rich in proteins and in 

 ferments which act on proteins, starch, and fat. Here, too, there is a 

 variety in result according as one or another nervous switch is closed ; 

 here, too, the variety is due, not to essential differences in the structure 

 of the activity or the nervous centres, but to their connection, by nervous 



