194 



EXCRETION BY THE KIDNEYS AND SKIN 



stance, it is found to be continued by three short canals, one 

 toward the upper, one toward the lower and one toward the 

 central portion of the organ. These are the three infun- 

 dibula. Each infundibulum, passing outward, subdivides 



Cortex. 



Boundary or 

 1 ^marginal 

 zone. 



^Papillary 



zone. 



FIG. 55- 



LS t of a pyramid of Malpighi; PF, pyramids of Ferrein; RA, branch of renal 

 artery with an interlobular artery; RV, lumen of a renal vein receiving an in- 

 terlobular vein; VR, vasa recta; PA, apex of a renal papilla; b, b, embrace the 

 bases of the lobules. (Stirling.) 



into two or three, or more, short cylinder-like canals which 

 receive the apices of the pyramids. These are the calyces, 

 each of which receives the apex of one or more pyramids. 

 The urine thus escaping from the pyramidal tubules passes 

 in succession through the calyces, infundibula, pelvis, and 

 thence into the ureter. 



