THE RABBIT 



445 



owing to the elasticity of the lungs as soon as the muscles 

 of inspiration relax, but this movement can be aided by 

 the contraction of certain other muscles, notably those of 

 the belly, which press the viscera against the diaphragm 

 from behind. 



The kidneys of the rabbit are a pair of dark-red bodies, 

 convex on the outer side and concave on the inner, which 

 lie on the dorsal wall of the peritoneal cavity, that on 



v.eff. 



FlG. 326. — Diagrams of the male genital and urinary 



apparatus of : 



A, The frog ; B, the dogfish ; C, the rabbit. 



bl., Bladder ; cl., cloaca ; k., kidney ; k'. t k". t anterior and posterior 

 regions of the same. In the dogfish these remain continuous 

 and are known as the " mesonephros " and " metanephros." In 

 the rabbit, regions roughly corresponding to those of the dogfish 

 become in the adult the "epididymis" and "kidney" respec- 

 tively. A, Testis (that of the rabbit is not lettered); ur., 

 ureter ; v.d., vas deferens (Wolffian duct) ; v.ejf., vasa efiferentia. 



The animal is lying on its back, the organs of the right side are 

 shown, and the bladder is turned to the left. 



the left side farther back than that on the right. Like 

 those of the dogfish and frog they consist of 

 Excretory and tubules, but they have no nephrostomes. It 

 Organs" will be recalled that, whereas the kidney of the 



frog has no distinction of regions, and dis- 

 charges solely by the Wolffian duct, that of the dogfish 

 (like that of the newt) has a narrow anterior region, which 

 takes little part in the secretion of the urine, and a larger- 

 hinder region, which is the main urinary organ and in the 

 male possesses a duct of its own, the ureter. In the 



