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Life and Health 



J 308, Minute Structure of the Kidneys. The pelvis of the 

 kidney is surrounded by reddish cones, about twelve in 

 number, projecting into it, called the pyramids of Malpighi. 



The apices of these cones, 

 known as the papillce, are 

 crowded with minute open- 

 ings, the mouths of the urinif- 

 erous tubules, which form the 

 substance of the kidney, and 

 which end at last in dilated 

 closed sacs called Malpighian 

 capsules. 



v ' 309. Function of the Kid- 

 neys. The Malpighian cap- 

 sules are really the beginning 

 of the tubules, for here the 

 work of excretion begins. 

 The thin wall of the capil- 

 laries within each capsule 

 separates the blood from the 

 cavity of the tubule. The 

 blood pressure on the deli- 

 cate capillary walls causes 

 the exudation of the -watery 



FIG. 109. 



Vertical Section of the 

 Kidney. 



A, pyramids of Malpighi ; B, apices, or 

 papilhe, of the pyramids, surrounded 

 by subdivisions of the pelvis known 

 as cups, or calices ; C, pelvis of the 

 kidney; D, upper end of ureter. 



portions of the blood through 

 the cell walls into the cap- 

 sule. The epithelial cell membrane allows the water of 

 the blood with certain salts in solution to pass, but rejects 

 the albumin. 



From the capsules the excretion passes through the 

 tubules into the pelvis of the kidneys, and on through the 

 ureters to the bladder. But the delicate epithelial walls 

 of the tubules through which it passes permit the inflow 



