CLASS AMPHIBIA 



491 



the bladder (10), where it is stored until expelled from the body- 

 through the anus. The kidney is composed of connective tissue 

 containing a large number of uriniferous tubules (Fig. 417, T), 

 each of which begins in a Mai pig/nan body (M), consisting of a 

 coiled mass of blood-vessels, the glomerulus, and an enclosing 

 membrane called Bowman's capsule. The excretions are carried 

 by the uriniferous tubules to a collecting tubule (C) and thence 

 into the ureter (U). Ciliated funnels, called nephrostomes (TV"), 

 occur in the ventral portion; these are in the young frog con- 

 nected with the renal tubules, but open into branches of the 



Fig. 417. — Diagram of a cross-section of the kidney of the frog. B, Bidder's 

 canal; C, collecting tubule; D, dorsal surface of kidney; L, lateral edge of 

 kidney; M, Malpighian body; N, nephrostome; T, uriniferous tubules; 

 U, ureter; V, renal portal vein. (From Holmes.) 



renal vein in the adult. Renal arteries (Fig. 414, re) and the 

 renal portal vein (Fig. 415, rti.pt; Fig. 417, V) bring blood into 

 the kidney. Blood leaves the kidney by way of the renal veins 



(Fig. 415, *»)■ 



The Reproductive System. — The sexes are separate. The 

 male can be distinguished from the female by the greater thick- 

 ness of the inner digit of his fore legs. The spermatozoa of the 

 male arise in the testes, pass through the vasa ejferentia (Fig. 

 416, A, 3) into the kidneys, then by way of Bidder's canal 

 (Fig. 417, B) to the ureter (Fig. 416, A, 6); and thence out 

 through the anus. 



Tie eggs arise in the ovaries of the female (Fig. 416, B, 5), 

 brea c out into the body-cavity, make their way into the coiled 



