THE NERVOUS SYSTEM 



THE PHYSIOLOGY OF THE NERVOUS SYSTEM 



167 



The work of the nervous system is to generate and to conduct 

 nerve impulses. It is divided between the central, peripheral 

 and sympathetic subsystems according to their adaptations. 



The functions of the nerve-cells are of two kinds. They act 

 as a controlling center of the nerve-fibers proceeding from them. 

 They are acted upon by stimuli conducted to them from without 



Blood capillaries in white matter. 



Blood-vessels 



%n gray 

 matter. 



Dorsal root of spinal nerve. 



Lig amentum 

 denticulatum. 



Ventral root oj 

 spinal nerve. 



Spinal 

 ganglion. 



Pia mater. 



Fig. 54. — Portion of spinal cord and membranes dissected. (Hill's Histology.) 



by the nerve-fibers. In the absence of such stimulation they 

 have the power of independent or automatic action. The nerve- 

 cells are also responsible for maintaining the axons in normal 

 condition for when the latter are cut off from the cell body they 

 die. 



The function of the nerve-fibers, according to Starling, is 

 simply that of conducting impulses from the sense organs at the 

 periphery to the central nervous system and transmitting effer- 

 ent impulses from this to the muscles and other of its servants. 

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