EXCRETION AND THE EXCRETORY ORGANS 469 



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 ef- 



ferent vein, carrying blood away from 



the glomerulus, breaks up into a close 



capillary network around the neighbor- 



ing 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 capillaries; one found in the 



capsules, and the second formed by the 



breaking up of their efferent veins. The 



capillary network in the pyramids is 



much less close than that in the cortex, Fl( Ti7o.-Diagram showing 



which gives reason tO SUSpect that most a kidney glomerulus and the 



. commencement of an unmfer- 



of the secretory work of the kidneys is ous tubule, a, afferent blood- 

 done in the capsules and convoluted Tflla&n c'ap'sulf an"d 

 tubules. The pyramidal blood flows ^Vfch the "5n ^e" 

 only through one set of capillaries, there c, involuted epithelium cover- 



. . ,. . ., , . , ing the vascular tuft; for the 



being no glomeruli in the kidney me- sa ke of distinctness it is rep- 



j ]] resented as a general wrapping 



for the whole tuft, but in na- 



The Renal Excretion. The amount ture it forms a close investment 



...-'- , . around each vessel of the glom- 



Of this Carried off from the Body in erulus; A, space in capsule into 



24 hours is subject to considerable 

 variation, being especially diminished 

 by anything which promotes perspira- convoluted portion, ff, of an 



, . , . ,.,. uriniferous tubule; o, granular 



tlOn, and increased by conditions, as epithelial cells; b, basement 



cold to the surface, which diminish the membrane - 

 skin excretion. Its average daily quantity varies from 1,200 

 to 1,750 cub. cent. (40 to 60 fluid ounces). The urine is a clear 

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

 ity is about 1,022, being higher when the total quantity excreted 

 is small than when it is greater, since the amount of solids dis- 

 solved 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. 



