354 THE ANATOMY OF THE HOBSE. 



44). The inferior ligament is a mesial fold attaching the bladder to the 

 pubic symphysis, and to the middle line of the abdominal wall in front 

 of the pubic brim. The lateral ligaments pass between the sides of the 

 bladder and the lateral walls of the pelvis, and in the adult the free 

 (anterior) edge of each contains the cord-like remains of the umbilical 

 artery. 



Again, the peritoneum, in descending from the roof of the cavity to 

 envelop the first part of the rectum, forms a suspensory fold — the meso- 

 redum, which is continuous in front with the colic mesentery. 



On each side the ureter and the vas deferens project narrow bands of 

 peritoneum, and the right and left vasa deferentia where they lie above 

 the bladder are connected by a triangular serous fold which contains 

 between its layers the prostatic vesicle. 



In the mare there are formed in an analogous manner the uterine 

 ligaments described at page 312. 



Directions. — The pelvis should now be either laid on its side, or sus- 

 pended in the natural position, and at a convenient height. A side view 

 of its contents is to be exposed by the following steps : With the saw 

 cut through the shaft of the ilium close above the cotyloid cavity. Make 

 another section through the same bone immediately external to the sacro- 

 iliac articulation. Remove the intermediate piece of bone, at the same 

 time separating the peritoneum from its inner aspect. Find the internal 

 pudic artery in the position shown in Plate 16. It will be either internal 

 to the sacro-sciatic ligament or in its texture. Trace it forwards and 

 backwards. It is accompanied by a satellite vein, and where the two 

 vessels pass above the small saoro-soiatic foramen they are crossed out- 

 wardly by the internal pudic nerve. This having been found should 

 be followed upwards. Without injury to the nerve and vessels, the 

 sacro-sciatic ligament may then be removed, taking care of the com- 

 pressor ooccygis and retractor ani muscles, which lie internal to the pos- 

 terior part of the ligament. 



The Internal Pudic Artery (Plates 46 and 47) is a branch of the 

 internal iliac, arising at the last lumbar vertebra. Entering the pelvis, 

 it descends obliquely downwards and backwards across the side of the 

 cavity, lying on the inner surface of the sacro-sciatic ligament or within 

 its texture (Plate 16). At the small sacro-sciatic foramen it passes with 

 an inward and backward direction, terminating in a manner that varies 

 with the sex. 



In the male it turns round the ischial arch and reaches the perineum, 

 where it penetrates the urethral bulb. Besides slender hsemorrhoidal 

 and perineal branches, it gives off the vesico-prostatic artery. 



The vesico-prostatic artery arises about the neck of the bladder, and 

 supplies the prostate, the vesicula seminalis, the posterior part of the 

 bladder, and the terminal part of the vas deferens. 



