146 



THE FROG 



Of.V 



A thin section shows the whole kidney to be made up of 

 a tangled mass of microscopic tubes (Fig. 46, ur. tu), so 



twisted together that 

 any section cuts them 

 in various planes, some 

 transversely, when they 

 appear as circles, others 

 longitudinally or ob- 

 liquely. Amongst these 

 urinary tubules or ne- 

 phridia, as they may be 

 called, are seen globu- 

 lar sacs, the Malpighian 

 capsules (;;/. cp), each 

 having in its interior a 

 little rounded bunch, 

 known as the glomerulus 

 (gl\ Very accurate ex- 

 amination of numerous 

 sections, as well as of 

 teased-out specimens, 



shows that each Mal- 

 '/- 



FIG. ^.-Diagram of a single urinary tubule pighian CapSUk (Fig. 47 , 



with its blood-vessels to illustrate the /;/> c p\ J s connected with 

 structure 01 the trog s kidney. f '' 



afv. afferent vessel I of glomerulus ; C p capil- a ur i na ry tubule (ur. tll\ 

 l.irv network nf kirinev ! cf. 71. efferent J 



to which it forms a 

 blind, bulb-like end. 

 The tubule itself winds 

 through the substance of 

 the kidney, is joined by 

 other tubules, and finally discharges into the ureter (ur). 

 The tubules are lined with somewhat cubical cells of 

 glandular epithelium, which, in some parts (ur. tu, ur. tu"\ 



lary network or kidney; ef.v. enetent 

 vessel of glomerulus ; gl. glomerulus ; 

 in. cp. Malpighian capsule, showing epi- 

 thelium (which in reality also covers the 

 glomerulus) ; nst. ciliated nephrostome ; 

 r. a. renal artery; r. pt. v. renal portal 

 vein ; r. v. renal vein ; ur. ureter ; ur. tu., 

 ur. tu'., ur. tu.", ur. tu.'", different por- 

 tions of urinary tubule, showing epithelium 



and cilia. 



