656 MAMMALIA. 



kidneys, their ducts the ureters, and a reservoir or bladder, 

 into which these open. The kidneys and their ducts are 

 formed from the metanephros and metanephric ducts of the 

 embryo. The bladder arises as a diverticulum from the 

 hind end of the gut, being in fact a remnant of the intra- 

 embryonic part of the allantois. It loses its connection 

 with the gut, and the ureters which originally opened into 

 the rectum follow the bladder and open into it. 



The kidneys are dark red ovoid bodies lying on the dorsal 

 wall of the abdomen ; the one on the left is further down 

 than that on the right, because of the position of the stomach 

 on the left side. When a kidney is dissected, a marked 

 difference is seen between the superficial cortical part and 

 the deeper medullary substance. On papillae or pyramids 

 in the very centre the coiled excretory tubules open, and 

 empty the water and waste products into the " pelvis " or 

 mouth of the ureter. 



The ureters run backward along the dorsal wall of the 

 abdomen, and open into the bladder, a thin-walled sac lying 

 in front of the pelvic girdle. 



In front of each kidney lies a yellow suprarenal body of 

 doubtful physiological significance. 



Reproductive organs. — (a) Male. — The testes arise on 

 the dorsal abdominal wall near the kidney, but as the rabbit 

 becomes sexually mature, they are loosened from their 

 original attachment, and pass out on the ventral surface, as 

 if by a normal rupture, into the scrotal sac. A spermatic 

 cord, consisting of an artery, a vein, and a little connective 

 tissue, runs from the abdomen to the testis. 



The testis is attached to the base of the scrotal sac, and 

 is bordered by a mass of convoluted tubes — the epididymis 

 — consisting of the caput epididymis anteriorly, the larger 

 cauda epididymis posteriorly, and a narrow band between 

 them. The cauda epididymis is connected to the scrotal 

 sac by a short cord or gubernaculum. 



Through the tubes of the epididymis (the modified meso- 

 nephros) the spermatozoa developed in the testis are 

 collected into the vas deferens (the modified Wolffian duct), 

 which arises from the cauda epididymis, ascends to the 

 abdomen, loops round the ureter, and, passing dorsally to 

 the bladder, opens beside its fellow into a median sac 



