196 Anatomy of the Rabbit. 



3. The urinary bladder (vesica urinaria) lies in the ventral 

 posterior portion of the abdominal cavity. It is a muscular sac, 

 capable of a considerable amount of distension, but usually found 

 in preserved animals in a greatly contracted condition. Its rounded 

 anterior end, the vertex, projects forward into the abdominal 

 cavity, while its posterior portion or fundus, narrows to a canal, 

 the urethra, which receives on its dorsal wall the apertures of the 

 genital ducts and those of the related glands. The connections 

 may be made out as follows : 



(a) The peritoneum is reflected from the ventral surface of the 

 rectum in the male and from the uterus in the female, to the 

 bladder, and aftier investing the latter passes to the ventral 

 abdominal wall. The dorsal peritoneum forms in the male 

 a double rectovesical fold (plica rectovesicalis) , and in the 

 female a similar vesicouterine fold, a recess of considerable 

 extent (rectovesical or vesicouterine pouch) being left 

 becween the adjacent structures. 



The ventral peritoneum forms a broad median vertical 

 sheet, the middle umbilical fold (plica umbilicalis media). 

 The free edge of this fold, extending from the vertex of the 

 bladder to the umbilicus, contains a slender cord, the middle 

 umbilical ligament (Hg. umbilicale medium) . The latter 

 marks the position of the peripheral portions of the um- 

 bilical arteries in the foetus. 



(b) The umbilical artery (a. umbilicalis) , a branch of the hypo- 

 gastric, passes along the side of the bladder to the vertex. 

 From the base of the artery branches are given off to the 

 ureter (a. urecerica) and related porcions of the genital ducts. 



B. The Male Genital Organs. 



I. Continue the median ventral incision of the skin backward 

 along the symphysis to the penis. Reflect the skin on both sides 

 to clear the attachments of the penis to the ischium, and on the left 

 to a point beyond the scrotum. Note the cremaster muscle 

 (m. cremaster), a thin layer of muscle fibres forming the outer 

 layer of the sac of the testis. It is continuous with the internal 

 oblique muscle of the abdominal wall, and also contains fibres 



