CHAP. XVI.] 



ELIMINATION. 



183 



papilla of the pyramids into the pelvis of the kidney. (Vide 

 Fig. 109.) 



The tubules are composed of basement membrane, lined 

 throughout by epithelium 

 cells. The cells vary in 

 the different parts of a 

 tubule, some being more 

 especially adapted to secre- 

 tory purposes than others. 



The blood-supply of the 

 kidney. For its size, the 

 kidney is abundantly sup- 

 plied with blood. The 

 renal artery, coming di- 

 rectly from the aorta, 

 divides as it enters the 

 hilus of the kidney into 

 branches, which, slipping 

 around the pelvis, pass 

 inwards between the pyra- 

 mids. On reaching the 

 boundary line between the 

 cortex and the medulla, 

 the branches divide lat- 

 erally to form more or 

 less complete arches, (the 

 veins also divide in a 

 similar manner to form 

 venous arches). From the 

 arterial arches, vessels pass 

 upwards through the cor- 

 tex, giving off at intervals . 



p . (Cadiat.) a, part of arterial arch; b, arterial 



tiny arteries, each of which branch passing upwards through the cortex; 



^ t h (lilnrpfl pom- c, gloraerul us; <Z, efferent vessel; f, raeshwork 



of capillaries; /, straight arterial vessels of 

 meilCement or capsule of medulla; g, venous arch; h, straight veins of 



a uriniferous tubule. medulla - 



These tiny arteries, entering the capsule, are spoken of as 

 afferent vessels. They push the thin walls of the capsule 

 before them, break up into a knot of capillary vessels, called a 

 glomerulus, and finally issue from the capsule as efferent ves- 



FIG. 107. VASCULAR SUPPLY OF KIDNEY. 



