THE BLADDER 2O7 



slightly inward behind the peritoneum, a distance of some 18 

 inches to the base of the bladder. In the female the cervix 

 uteri lies between the two ureters just before they enter the 

 bladder. They penetrate the bladder wall obliquely, their 

 course therein being nearly an inch long. The effect of this 

 arrangement is that distention of the bladder closes the open- 

 ing more closely instead of causing regurgitation into the 

 ureter. The ureter is composed of three coats. The outer 

 is fibrous, the middle muscular, and the internal mucous. 



The bladder serves as a reservoir for the urine until such 

 time as it is convenient for it to be evacuated. This organ, 

 when empty, lies deep in the pelvis in front of the rectum 

 in the male and of the uterus in the female. When moder- 

 ately distended it will hold about a pint, has an ovoid shape 

 and rises to the brim of the pelvis. It also has three coats. 

 The outer is peritoneal, and covers the posterior and small 

 parts of the lateral and anterior surfaces only. Its lower 

 limit posteriorly is the entrance of the ureters. The middle 

 layer is muscular. The fibers, which are non-striped, are 

 disposed in three sheets. Their contraction compresses the 

 contents from all directions. Embracing the neck (outlet) 

 of the bladder is a thick band of plain muscle tissue known 

 as the sphincter vesicce. The tonic contraction of this mus- 

 cle prevents the continual escape of urine. The inner coat 

 of the bladder is mucous. It is rather thick, and loosely ad- 

 herent to the subjacent muscular coat except over the corpus 

 trigonum where it is closely attached. The corpus trigonum 

 is a triangular body of fibrous tissue just underneath the 

 mucous membrane; its apex is at the origin of the urethra, 

 and its other angles are at the vesical openings of the uret- 

 ers. 



Absorption from the intact mucous membrane of the blad- 

 der takes place very sparingly, if at all. Abrasions of the 

 membrane from any cause allow absorption to occur; and 

 this fact may be made use of to locate lesions giving rise to 

 hematuria. Iodide of potassium injected into the bladder 



