54 



THE NERVOUS SYSTEM 



FIG. 23 



tr - 



--rm 



-be 



it; (4) to direct glandular function: 

 (a) actuating it, (6) inhibiting it; (5) 

 to direct tissue-nutrition : trophism. 



1. The nervous system, in represent- 

 ing consciousness, as the general though 

 careless presumption is, performs its 

 most mysterious function. Yet were 

 it not for the fact that a blow on the 

 brain destroys consciousness, while one 

 on a mass of muscle does not, we could 

 not perhaps claim that the nervous sys- 

 tem transmits consciousness any more 

 than does the muscular tissue, or the 

 bones, or the protoplasm of the liver. 

 Consciousness and living bodies, so far 

 as we know, are inseparable; more than 

 this cannot be said. How completely 

 the nerves represent the mind, then, 

 we do not know, but they apparently 

 do so by unifying the functions of the 

 organism, and by coordinating the pro- 

 toplasmic activities into the " physical 

 basis' ' of a personality. 



2. The animal body, like the mind, 

 is a part of Nature, and as such is in the 

 closest possible relation with its environ- 

 ment. The nervous system has to adapt 

 the organism to this environment, 

 especially to changes, among others, 

 in the kind and amount of its nutrients 

 and in its amount of moisture, heat, 

 pressure, light, and oxygen. All these 

 and numerous other conditions help to 

 determine the reactions of the body, 

 and should be regarded by the dys- 

 chophysical organism every moment 

 of its life. It is the inward (afferent 

 or centripetal) impulses which convey 

 to the reflex and voluntary centers of 

 the nervous system knowledge of these 

 and many other conditions of the envi- 

 ronment. 



3. In the direction of muscular 

 contractions, producing both molec- 

 ular and molar movements, the ner- 

 vous system controls and coordinates 



the deliberate voluntary movements, and the instinctive and emotional 

 (reflex) reactions of the organism. It does this both by actuating them 



le 



The brain, cord, and sympathetic chain 

 of the dove: vh, forebrain (hemispheres); 

 lo, optic lobe; kh, cerebellum; ob, me- 

 dulla oblongata ("bulb"); tr, trigeminal 

 (fifth cranial) nerve; g, spinal ganglion; 

 rm, spinal cord; sy, sympathetic; be, dor- 

 sal enlargement; le, lumbar enlargement; 

 /, filum terminale. (B. Haller.) 



