854 PHYSIOLOGY OF DIGESTION AND SECRETION. 



contracts spontaneously at intervals of ten to twent}' seconds (rab- 

 bit), the contraction begnining at the kidney and progressing 

 toward the bladder in the form of a peristaltic wave and with a 

 velocity of about 20 to 30 mms. per second. The result of this 

 movement should be the forcing of the urine into the bladder in a 

 series of gentle, rhythmical spurts, and this method of filling the 

 bladder has been oloserved in the human being. Suter and Mayer r 

 report some observations upon a boy in whom there was ectopia 

 of the bladder, with exposure of the orifices of the ureters. The 

 flow into the bladder was intermittent and was about equal upon the 

 two sides for the time the child was under observation (three and 

 a half days). 



Histological examination shows that the ureter is provided 

 with an intrinsic nervous supply. Nerve plexuses of ganglion cells 

 and nerve fibrils surround the muscular coat on both sides, and 

 doubtless make connections with the muscle-fibers. It is prob- 

 able, therefore, that as in the case of the intestines the orderly- 

 progress of the peristaltic wave is regulated through this intrinsic 

 nervous apparatus. Presumably the local stimulus that originates 

 the contraction is to be found in the pressure of the urine, although 

 there are some indications that the chemical composition of the 

 urine may also have an effect. In addition to this intrinsic ner- 

 vous system the ureter receives extrinsic fibers from the splanchnic 

 nerve and the inferior mesenteric ganglion (thoracic autonomics) 

 and from the pelvic nerve (sacral autonomics). The fibers from 

 the splanchnic and pelvic nerves excite contractions, while those 

 from the inferior mesenteric cause inhibition, f It would seem 

 probable therefore that the activity of the ureters must be subject 

 to reflex influences of an excitatory and inhibitory character 

 through these extrinsic fibers. 



Movements of the Bladder. — The bladder contains a muscular 

 coat of plain muscle tissue, which, according to the usual descrip- 

 tion, is arranged so as to make an external longitudinal coat and an 

 internal circular or oblique coat. A thin, longitudinal layer of 

 muscle tissue lying to the interior of the circular coat is also de- 

 scribed. The separation between the longitudinal and circular 

 layers is not so definite as in the case of the intestine; they seem, 

 in fact, to form a continuous layer, one passing gradually into the 

 other by a change in the direction of the fibers. At the opening of 

 the bladder into the urethra, the musculature in the submucosa is 

 strengthened to form a ring around the orifice and along the begin- 

 ning of the urethra which is supposed to function as a sphincter, the 

 internal sphincter or sphincter vesicce internus. Around the urethra, 



* "Archiv f. exper. Pathologie imd Pharmakologie," 32, 241, 1893. 

 t Sata,ni, "American Journal of Phvsiologv," 49, 474, 1919, and 50, 342, 

 1919. 



