676 MAMMALIA. 



which these open. The kidneys and their ducts are formed 

 from the metanephros and metanephric ducts of the em- 

 bryo. The bladder arises as a diverticulum from the hind 

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

 bryonic 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 dif- 

 ference 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 sacs. 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 col- 

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

 which arises from the cauda epididymis, ascends to the 

 abdomen, extends round to the dorsal surface of the neck of 



