ANATOMY OF THE URINARY PASSAGES. 179 



when the tube is flaccid, which are easily effaced by disten- 

 tion. The epithelium exists in several layers, and is remark- 

 able for the irregular shape of the cells. They present, 

 usually, numerous dark granulations, and one or two clear 

 nuclei, with distinct nucleoli. Some of the cells are flat- 

 tened, some are rounded, and some are caudate, with one or 

 two prolongations. 



Passing to the base of the bladder, the ureters become 

 constricted, penetrate the coats of this organ obliquely, 

 their course in its walls being a little less than one inch 

 in length. This valvular opening allows the free passage 

 of the urine from the ureters, but compression or distention 

 of the bladder closes the orifices and renders a return of the 

 fluid impossible. 



The bladder, which serves as a reservoir for the urine, 

 varies in its relations to the pelvic and abdominal organs 

 as it is empty or more or less distended. When perfectly 

 empty, it lies deeply in the pelvic cavity, and is then a 

 small sac, of an irregularly triangular form. As it be- 

 comes filled, it assumes a globular or ovoid form, rises up 

 in the pelvic cavity, and, when excessively distended, may 

 project into the abdomen. When the urine is voided at the 

 normal intervals, the bladder, when filled, contains about a 

 pint of liquid ; but under pathological conditions, it may 

 become distended so as to contain ten or twelve pints, and in 

 some instances of obstruction, it has been found to contain 

 even more. The bladder is usually more capacious in the 

 female than in the male. It is held in place by certain 

 ligaments and folds of the peritoneum, which it is unneces- 

 sary to describe in this connection, but which are so arranged 

 as to allow of the various changes in volume and position 

 which the organ is liable to assume under different degrees 

 of distention. 



The anatomy of the coats of the bladder possesses a cer- 

 tain amount of physiological interest. These are three in 

 number. The external coat is simply a reflection of the 



