244 ANATOMY OF THE RABBIT 



(d) The fibrous coat (tunica fibrosa) of the kidney may be 

 stripped from the surface. 



In the rabbit the kidney is not lobulated. Hence there is a single 

 renal papilla, and the division of the kidney substance into renal 

 pyramids is imperfectly expressed. The medullary substance, how- 

 ever, possesses a slightly divided margin. 



The cortical substance is of darker coloration than the medullary 

 in the natural condition, but in embalmed animals the colour relations 

 are usually reversed. 



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

 terior 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 dorsolateral surface of 

 the rectum in the male and from the vagina in the female, 

 to the bladder, and after investing the latter passes to the 

 ventral abdominal wall. The peritoneum dorsal to the 

 bladder forms in the mak a paired retrovesical fold (plica 

 recto vesicalis), and in the female a similar vesicouterine 

 fold, the ureter in each case running in the edge of the fold 

 and a recess of considerable extent (rectovesical or vesi- 

 couterine pouch) being left between the adjacent structures. 

 The ventral peritoneum forms a broad median vertical 

 sheet, the middle umbilical fold (plica umbilicalis media) 

 between the bladder and the ventral abdominal wall. The 

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

 bladder to the umbilicus, contains a slender cord, the 

 middle umbilical ligament (lig. umbilicale medium). The 

 latter marks the position of the peripheral portions of the 

 umbilical arteries in the foetus, where they run beyond the 

 bladder into the umbilical cord to reach the placenta (Fig. 

 65) . The middle umbilical fold is often heavily laden with fat. 



