344 SPLANCHNOLOGY. 



by peritoneum, which holds them against the lateral walls of the 

 abdomen and pelvis, terminating at the postero-superior part of 

 the bladder, which they enter on each side by piercing its coats 

 in a very oblique manner, and so leading to the formation of a 

 valve which prevents regurgitation of the urine. 



The ureters are supplied with blood by twigs from the renal, 

 spermatic, and vesical arteries. The nerves come from the 

 spermatic and hypogastric plexuses. 



BLADDER. 



The bladder, a musculo-membranous organ, serves as the 

 reservoir for the urine, and is situated within the pelvic cavity, and 

 when full projecting into the abdomen. It consists of a fundus, 

 or body, and a neck. The fundus when full is ovoid, and turned 

 forwards, having a cicatrix, which marks the site of the urachus. 

 The neck is turned backwards, and is continuous with the urethra. 

 The bladder is related above with the vesiculaB seminales and 

 rectum in the male, in the female with the vagina and uterus, 

 which are interposed between it and the rectum ; below with the 

 floor, and laterally with the walls of the pelvis. 



The bladder consists of three coats ; mucous, muscular, and 

 serous ; the latter is only a partial covering, being a continuation 

 of the peritoneum, clothing the anterior part of the organ it 

 becomes reflected from it in several places, constituting the false 

 ligaments of the bladder. The muscular coat consists of two 

 layers of smooth muscular fibres ; an external longitudinal one, the 

 detrusor urince, and an inner circular layer, thinly scattered over 

 the body, but denser at the neck, forming the sphincter vesicce. 

 The sphincter vesica3 is less developed in quadrupeds than in 

 man. There are also two bands of oblique fibres passing from 

 the posterior aspect of the ureters to the back of the prostate 

 gland. 



The internal mucous coat is pale, smooth, roseate, and loosely 

 attached to the muscular l.ayer by cellular tissue, which some 

 consider a fourth coat. It is thrown into rugce when the bladder 

 is empty, and provided with mucous follicles, most abundant at 

 the neck ; it is covered by stratified epithelium. Upon the 

 internal surface, between the openings of the ureters and com- 

 mencement of the urethra, is a smooth triangular space, the 

 trigonus vesicce, which is pale, sensitive, intimately attached to 



