432 THE HUMAN BODY. 



outside of the capsule and those involuted on the vessels, as 

 there would be in the interior of a rubber ball one side of 

 which was pushed in so as to nearly meet the other; this 

 cleft, into which any liquid transuded from the vessels must 

 enter, opens by a narrow neck, d, into the commencement of 

 the first contorted part of an uriniferous tubule. The effer- 

 ent vein, carrying blood away from the glomerulus, breaks 

 up into a close capillary network around the neighboring 



tubules of the cortex. From these 

 capillaries the blood is collected 

 into the renal vein. Most of the 

 blood flowing through the kidney 

 thus goes through two sets of capil- 

 laries; one found in the capsules, 

 and the second formed by the 

 breaking up of their efferent veins. 

 The capillary network in the pyra- 

 mids is much less close than that 

 in the cortex, which gives reason to 

 suspect that most of the secretory 

 work of the kidneys is done in the 



FIG. 134. Diagram showing a capsules arid convoluted tubules. 

 n an Sdnffe^ The pyramidal blood flows only 



through one set of capillaries, there 

 **S no glomeruli in the kidney 



vein e issues; c, involuted epithe- rnprlnlla 

 Hum covering: the vascular tuft; " 



for the sake of distinctness it is The Renal Secretion. The 



represented as a general wrapping 



for the whole tuft, but in nature amount of this carried off from the 



it forms a close investment . 



around each vessel of the glo- Body in 24 hours IS SU Dject to CO11- 



merulus; A. space in capsule into . , , , ... , . ,, 



which liquid transuded from siderable variation, being especially 

 ng diminished by anything which pro- 

 : motes perspiration, and increased 

 " b y conditions, as cold to the sur- 

 brane - face, which diminish the skin ex- 



cretion. Its average daily quantity varies from 1200 to 1750 

 cub. cent. (40 to 60 fluid ounces). The urine is a clear 

 amber-colored liquid, of a slightly acid reaction; its specific 

 gravity is about 1022, being higher when the total quantity 

 excreted is small than when it is greater, since the amount of 

 solids dissolved in it remains nearly the same in health; the 

 changes in its bulk being dependent mainly on changes in 

 the amount of water separated from the blood by the kidneys. 



