THE ADRENAL BODIES 477 



Here the mucous membrane is closely attached and does not form folds. From 

 each ureteral orifice (Orificium ureteris) a fold of mucous meml^rane (Plica ureter- 

 ica) passes backwartl and inward, uniting with its fellow to form a median crest 

 (Crista urethralis) in the first part of the urethra. The ureteral orifices are a little 

 more than one inch (ca. 3 cm.) apart. The terminal part of the ureter, after pierc- 

 ing the muscular coat of the blatlder, passes for a distance of about an inch (ca. 

 2 to 3 cm.) Jjetween the muscular and mucous coats before piercing the latter; this 

 arrangement constitutes a valve which prevents al)Solutely the return of the urine 

 from the bladder into the ureter. The internal urethral orifice (Orificium urethrge 

 internum) lies at the apex of the trigonum, and is about an inch and a half (ca. 

 4 cm.) behind the ureteral orifices. The mucous membrane is covered with transi- 

 tional epithelium like that of the ureter and renal pelvis. It contains lymph 

 nodules. 



Blood-supply. — This is derived chiefly from the vesico-prostatic branch of 

 the internal pudic artery. It is also supjjlied by small twigs from the obturator 

 and umbilical arteries. The veins terminate chiefly in the internal pudic veins. 

 They form plexuses posteriorly. 



Lymph Vessels. — These form plexuses on both surfaces of the muscular coat. 

 They go to the internal iliac and lumbar glands. 



Nerves. — The nerves are derived from the pelvic plexus (sympathetic and 

 ventral branches of third and fourth sacral nerves). They form a plexus in the 

 submucosa which presents microscopic ganglia. 



In the foetus and now-born animal the bladder is situated chiefly in the alxlomen. It is 

 long, narrow, and fusiform. Its abdominal end lies at the umbilicus, through which it is con- 

 tinued by the urachus to the extra-embryonic part of the allantois. As the pelvis increases in 

 size and the large intestine grows, the bladder retracts into the pelvis and changes its form. 



The urethra will be described with the genital organs. 



THE ADRENAL BODIES 



The adrenal bodies or suprarenal glands (Glandulse suprarenales)^ are two 

 small, flattened organs, which lie in contact with the anterior part of the inner 

 border of the kidneys (Figs. 376, 377). They are ductless. 



In the horse they are red-brown in color, about three and a half to foiu- inches 

 (ca. 9 to 10 cm.) long, one to one and a half inches (ca. 3 to 4 cm.) wide, and about 

 half an inch or more (ca. 1 to 5 cm.) in thickness. The weight varies from one to two 

 ounces (ca. 28 to 5G gm.). 



The right adrenal is related internally to the posterior vena cava, to which it is 

 adherent. Its anterior part curves dorsally around the inner l)order of the right 

 kidney. Its posterior part is flattened and is related ventrally to the pancreas 

 and cificum, dorsally, to the right renal vessels. The anterior extremity is con- 

 cealed in the renal impression of the liver; the posterior is related to the ureter. 



The left adrenal is a little shorter than the right one, and its extremities are 

 rounded; it is usually curved, so that its internal border partly embraces the 

 anterior mesenteric artery. Its dorsal surface is related to the kidney, the renal 

 artery, the aorta, and the left coeliaco-mesenteric ganglion. The ventral surface 

 is in relation with the left extremity of the pancreas and the root of the great 

 mesentery. The posterior extremit\' often curves inward behind the anterior 

 mesenteric artery; it is related behind to the left renal vein. 



When hardened iyi situ the adrenals present several features not evident in the soft organs. 

 The anterior part of the right adrenal is twisted upward and outward over the inner margin of 

 the kidney, so that this part is prismatic and has three surfaces; of these, the concave outer one 

 is applied to the kidney, the dorsal one is related to the right crus of the diaphragm and the liver, 



'From the standpoint of comparative anatomy the term "adrenal" seems decidedly 

 preferable to "suprarenal." 



