Integrative Systems 185 



fibers of exciters whose cell-bodies are in the lateral ganglions. They 

 are, therefore, purely gray rami (Fig. 159). Certain spinal nerves in 

 the posterior lumbar and sacral region may have only gray rami. 



The peripheral distribution from the lateral ganglions, aside 

 from that which is effected through the gray rami, is as follows (Figs. 

 157, 159) : The cervical ganglions are constituted largely of exciter- 

 neurons whose fibers are assembled into nerves passing forward to the 

 region of the head, where their distribution includes smooth muscles of 

 blood-vessels, secretory cells of salivary and lacrimal glands, and 

 the intrinsic muscles of the eye. All of the cervical ganglions send 

 exciters to the heart. It is to be emphasized that, in all of this dis- 

 tribution, the exciter-fiber goes directly to a muscle-cell or a gland-cell, 

 not to any terminal ganglion. From the stellate and adjacent 

 thoracic ganglions, exciter nerves pass to the lungs. Most of the 

 connectors which enter the more posterior thoracic and the lumbar 

 lateral ganglions pass through the ganglions (i.e., without making 

 synapses with exciters in the ganglions) and become assembled into the 

 paired splanchnic nerves which pass on to the celiac, anterior mesen- 

 teric, and posterior mesenteric collateral ganglions. Similarly, most 

 of the connectors of the two or three sacral lateral ganglions emerge 

 without synapse and join to form a pair of pelvic nerves which dis- 

 tribute to numerous terminal ganglions of the "large" intestine, 

 urinary bladder, prostate gland, and genital organs, but appar- 

 ently not to the uterus. 



Collateral ganglions (Figs. 157, 159) : connectors entering the 

 celiac ganglion via the splanchnic nerves make synapse there with 

 exciters which pass to smooth muscle-fibers or secretory cells of the 

 stomach, liver, pancreas, and spleen. Similarly, connectors to the 

 anterior mesenteric ganglion are there related to exciters which 

 distribute to the entire "small" intestine and more or less of the 

 anterior region of the "large" intestine, and to the kidneys. The 

 celiac and anterior mesenteric ganglions may be closely joined. 



The distribution from the posterior mesenteric ganglion is con- 

 fused by the close relation of the ganglion to a group of lumbar con- 

 nectors which may pass through the ganglion without synapse within 

 it, or may pass by the ganglion without entering it and go on to a dis- 

 tribution which more or less overlaps that of exciters from the ganglion. 

 These through, or by-passing, connectors combine into a pair of hypo- 

 gastric nerves (Fig. 157, 20) which go to pelvic viscera. The walls of 

 these viscera — the rectum, urinary bladder, uterus, and other 

 urinogenital parts — are invested by a maze of plexuses into which pass 

 not only the hypogastric nerves but also the sacral or pelvic nerves. 

 Since the nerves of both of these pairs are constituted of connectors, 



