630 



THE AUTONOMIC NERVOUS SYSTEM 



to act primarily upon the parasympathetic system, and chiefly upon 

 the cranial ganglia and their ramifications. 



The Function of the Autonomic System. The innervation of the 

 striated musculature is effected by fibers which arise in the cerebrum, 

 cerebellum and spinal cord and pursue a perfectly straight course 

 to the periphery. Those fibers, on the other hand, which are con- 

 cerned with the vegetative processes, do not pass directly to the 

 motor end-organs, but are first relayed into the sympathetic system. 

 The latter, therefore, may be regarded as a siding upon the cerebro- 

 spinal tract. In its amplified form this statement signifies that the 

 impulses apportioned to striated muscle are distinctly cerebrospinal 

 in their origin and remain so throughout their course, while those 



FIG. 312. CELLS FROM THE GANGL. CERVICALE SUPREMUM OF MAN. 

 A and B, Cells with short dendrites; (7, cell with long dendrites; a, axon. (Cajal.) 



distributed to smooth and cardiac muscle tissue, as well as to the glands, 

 do not remain so, but presently assume the characteristics of the auto- 

 nomic or sympathetic system. It has been stated above that the 

 effectors are limited in number, because only two structural units 

 enter into their formation, namely, muscle tissue and glandular tissue. 

 The former, however, presents itself as striated, smooth and cardiac 

 muscle. We now observe that the smooth and cardiac muscle tissues, 

 together with the glandular tissue, form the typical motor organs 

 of the autonomic system, while the striated muscle alone remains dis- 

 tinctly cerebrospinal in its character. 



In further analysis of this fact it becomes immediately apparent 



