5 4 THE IN VOL UNTAR Y NER VO US S YSTEM 



the cloacal musculature which is supplied with motor nerves 

 from nerve cells connected with the pelvic nerves. All observers, 

 from the earliest times, are agreed that stimulation of this nerve 

 causes a strong contraction of the bladder in all animals which 

 possess one. 



The sacral outflow differs from the thoracico-lumbar in a 

 striking manner ; whereas the latter passes into well-defined 

 ganglia, which give origin to efferent fibres often having to travel 

 to some distance before reaching their destination, the former 

 pass directly, not into a single ganglion, but into a nerve plexus, 

 throughout which scattered nerve cells or small groups of nerve 

 cells are found, lying close to the muscle itself. This pelvic 

 plexus extends over the surface of the bladder and rectum, so that 

 it is possible to speak of it as made up of a vesical and rectal 

 plexus. Fibres pass from it to supply the large intestine, bladder, 

 and uro-genital tract. Langley and Anderson have followed out 

 the course of the fibres to a considerable extent into and through 

 this plexus, and have determined the end stations of many of the 

 connector fibres by means of the degeneration method. The 

 pelvic nerve was cut, and time allowed for degeneration of its 

 medullated fibres. The different branches were then teased out 

 after staining with osmic acid, and the number of degenerated 

 fibres counted in each nerve examined. The results are shown in 

 an illustration which is reproduced on the opposite page (Fig. 9). 



The pelvic nerve divides primarily into an anterior and 

 posterior branch ; the latter connects with the rectal plexus, from 

 which arise nerves running directly into the intestinal wall ; these 

 nerves Langley and Anderson designate as sacral colonic nerves, 

 in centra-distinction to the lumbar colonic nerves arising frcm the 

 inferior mesenteric ganglion. They have shown that these sacral 

 colonic nerves pre-eminently cause contraction of the muscles of 

 the large intestine, while the lumbar colonic nerves cause essen- 

 tially inhibition. 



The first ganglion, or rather group of ganglia, lying in the 

 rectal plexus on this posterior branch of the pelvic nerve, is a 

 fairly conspicuous one ; and they speak of it as the ganglion con- 

 cerned with the motor nerves to the large intestine. An ex- 

 amination of the analysis of these sacral colonic nerves, as given 

 in Fig. 9, shows that the large majority of the medullated fibres 

 of these nerves are degenerated after section of the pelvic nerve, 



