762 PHYSIOLOGY OF DIGESTION AND SECRETION. 



bladder has been observed in the human being. Suter and Mayer* 

 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). 



The causation of the contractions of the ureter musculature is 

 not easily explained. Engelmann finds that artificial stimulation 

 of the ureter or of a piece of the ureter may start peristaltic con- 

 tractions which move in both directions from the point stimulated. 

 He was not able to find ganglion cells in the upper two-thirds of the 

 ureter and was led to believe, therefore, that the contraction orig- 

 inates in the muscular tissue independently of extrinsic or intrinsic 

 nerves, and that the contraction wave propagates itself directly 

 from muscle cell to muscle cell, the entire musculature behaving 

 as though it were a single, colossal, hollow muscle fiber. The liber- 

 ation of the stimulus which inaugurates the normal peristalsis 

 of the ureter seems to be connected with the accumulation of urine 

 in its upper or kidney portion. It may be supposed that the urine 

 that collects at this point as it flows from the kidney stimulates 

 the muscular tissue to contraction, either by its pressure or in some 

 other way, and thus leads to an orderly sequence of contraction 

 waves. It is possible, however, that the muscle of the ureter, like that 

 of the heart, is spontaneously contractile under normal conditions, 

 and does not depend upon the stimulation of the urine. Thus, 

 according to Engelmann, section of the ureter near the kidney does 

 not materially affect the nature of the contractions of the stump 

 attached to the kidney, although in this case the pressure of the 

 urine could scarcely act as a stimulus. Moreover, in the case of 

 the rat, in which the ureter is highly contractile, the tube may be 

 cut into several pieces and each piece will continue to exhibit period- 

 ical peristaltic contractions. It does not seem possible at present 

 to decide between these two views as to the cause of the contrac- 

 tions. The nature of the contractions, their mode of progression, 

 and the way in which they force the urine through the ureter seem, 

 however, to be clearly established. Efforts to show a regulatory 

 action upon these movements through the central nervous system 

 have so far given negative results. 



Movements of the Bladder. The bladder contains a muscular coat 

 of plain muscle tissue, which, according to the usual description, 

 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 

 * "Archiv f. ex per. Pathologie und Pharmakologie," 32, 241, 1893. 



