FUNCTIONS 627 



Such fibers are a peculiarity of the spinal nerve roots chiefly in the thoracic 

 region. But they are also found in the second and third sacral nerves, and 

 constitute there the nervi erigentes which pass directly to the hypogastric 

 plexus. From the hypogastric plexus branches pass upward into the inferior 

 mesenteric ganglia and downward to the bladder, rectum, and generative 

 organs. These nerves, called by Gaskell pelvic splanchnic nerves, differ from 

 the rami viscerales of the thoracic region only in not communicating with 

 the lateral ganglia. The branches which pass upward from the thoracic 

 region to the neck, he calls cervical splanchnics, and the splanchnics proper 

 abdominal splanchnics. 



Functions. The researches of Gaskell and of Langley have done 

 much to clear up the former confusion as to the distribution and functions 

 of the sympathetic nerves. The sympathetic nerve fibers are distributed to 

 smooth muscle, to gland cells, and to cardiac muscle. These are all organs 

 which carry on their activities either automatically or reflexly. There is no 

 voluntary control of the function of such organs. 



The efferent sympathetic fibers supply the muscles of the vascular system, 

 to which they send the vaso-motor fibers, i.e., vaso- constrictor and cardiac 

 augmentor or accelerator; and vaso-inhibitory fibers, i.e., vaso-dilators. 

 They supply the muscles of the alimentary canal and of the urinogenital 

 system. The details of arrangement and functional control of these com- 

 plex systems have already been discussed in connection with the function of 

 the organ or part concerned. They supply the salivary, gastric, and pan- 

 creatic glands. 



According to Gaskell the functions of the main sympathetic ganglia are 

 the following: i. The sympathetic ganglia are aggregates of large numbers 

 of multipolar cells around which the medullated fibers of the white rami form 

 synapses. The branches of the cells are of the non-medullated fiber type. 

 Thus a medullated conduction is converted in the ganglia into a non-medul- 

 lated path beyond the ganglia. 2. The ganglion cells exercise a nutritive 

 influence over the tissues to which their fibers are distributed. 3. The num- 

 ber of preganglionic fibers entering the ganglia is not so great as that leaving, 

 since the cells are multipolar (not shown in the schematic figure 417). This 

 serves to multiply the influence of a relatively simple efferent preganglionic 

 conduction path and to extend it over a larger area the parts of which are 

 usually acting co-ordinatively. 



The sympathetic ganglia are not nerve centers in the usual sense. It is 

 better to regard them merely as distributing organs in which reflexes of cen- 

 tral origin and x comparatively simple type are distributed over relatively 

 large areas. These ganglia do not possess the power of reflex function. A 

 type of pseudo-reflex has been described depending on the law of neurone 

 reaction. But it is not supposed that such reflexes occur in the normal 

 animal. 



