THE SYMPATHETIC NERVE SYSTEM. 615 



the spheno-palatine ganglion and by way of the chorda tympani to the 

 submaxillary and sublingual ganglia. The fibers that leave the glosso- 

 pharyngeal nerve pass into the tympanic branch or nerve of Jacobson 

 and ultimately terminate around the otic ganglion. The fibers that 

 leave by the vagus nerve pass to the ganglia in the heart, stomach, and 

 small intestine. 



3. The pre-ganglionic fibers that arise from nerve-cells in the gray matter of 

 the sacral division of the spinal cord enter the ventral roots of the 

 second, third, and occasionally fourth sacral nerves. In the pelvis these 

 fibers leave the sacral nerves, enter the pudendal or pelvic nerve and are 

 finally distributed to ganglia in the pelvic cavity associated with pelvic 

 viscera and the external generative organs. 



Afferent Sympathetic Fibers. With the foregoing groups of efferent 

 fibers, the sympathetic nerves, in the thoracic and lumbar regions more 

 especially, contain a number of afferent fibers which when stimulated give 

 rise to sensations of pain or to reflex phenomena. The routes by which these 

 afferent fibers reach the spinal cord lead through the white rami into the 

 spinal nerve, thence into the dorsal roots to the spinal ganglia, where they 

 have their cells of origin. The number of afferent fibers in any trunk in 

 comparison with the efferent is quite small. 



FUNCTIONS OF THE AUTONOMIC NERVE SYSTEM. 



The view according to which the sympathetic ganglia are to be regarded 

 as independent organs endowed with functions of their own and in nowise 

 directly dependent for their activities on the spinal cord, is at the present time 

 very largely discarded. Peripheral structures cease to exhibit their charac- 

 teristic functions after division of the spinal nerves in connection with 

 their related ganglia. This does not exclude the possibility of the sym- 

 pathetic cell-body, in virtue of the interchanges between it and the blood 

 and lymph by which it is surrounded, maintaining its own nutrition and 

 exerting a favorable influence over the nutrition of the peripheral tissues 

 to which its post-ganglionic branches are distributed. 



The nerve-tissue in its entirety may be regarded as a single system which 

 may be functionally divided into a nerve system of animal and a nerve 

 system of vegetative life, according as the nerve energies originating in and 

 emanating from the central nervous system are transmitted directly to the 

 skeletal muscles or indirectly, through the intervention of a sympathetic 

 neuron, to visceral muscles and glands. In the former system but one neu- 

 ron, the spino-peripheral, connects the spinal cord proper with the muscle; 

 in the latter system there are two, the spino-ganglionic and the ganglio- 

 peripheral. 



From the distribution of the post-ganglionic fibers it may be inferred that 

 the activities of the vascular and visceral muscles, either in the way of aug- 

 mentation or inhibition, the activities of the muscles of the hair-follicles, and 

 of the epithelium of glands, are called forth by the ganglia in consequence of 

 the arrival of nerve impulses coming from the spinal cord through the pre- 

 ganglionic fibers. Experimental observations show this to be true. The 

 extent to which these different modes of activity manifest themselves in 



