524 



THE HUMAN BODY 



capillary vessels called the glomerulus, from which ultimately 

 an efferent vessel proceeds. Where the wall of the capsule, w, 

 Fig. 141, is doubled in before the blood-vessels, its lining cells 

 continue as a covering, c, to the latter, closely adhering to the 

 vascular walls. A space, A, is left between the epithelial cells of 

 the 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 nec%, 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 (Fig. 140). 

 From these capillaries the blood is col- 

 lected 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 ef- 

 ferent veins. The capillary network in 

 FIG. 141. Diagram showing the pyramids is much less close than 



a kidney glomerulus and the ^ at in thp rortpY whirh ffivps reason to 

 commencement of an urinifer- tnat m tne jGX > Wni n 1Ves 



ous tubule, a, afferent blood- suspect that most of the secretory work 



vessel pushing ia the wall, w, .,,,., . , . . , 



of a Malpighian capsule and of the kidneys is done in the capsules and 



fr^hi^h^e^TLi^ convoluted tubules. The pyramidal 



c, involuted epithelium cover- blood flows only through one set of 



mg the vascular tuft; for the .* 



sake of distinctness it is rep- capillaries, there being no glomeruli in 



resented as a general wrapping ,, i ., j ,, 



for the whole tuft, but in na- the kidney medulla. 

 ^SS^S^JfSfSSi The Renal Excretion. The amount 



erulus; A, space in capsule into of this carried off from the Body in 



which liquid transuded from rt . , . . . 111 



the vessels of the glomerulus 24 hours is subject to considerable 



passes; d, neck of capsule pass- V o r j fl t; on hpincr psnppiallv diminished 



ing into commencement of first variation, I .ing especially 



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



unmferous tubule; o, granular . . 



epithelial cells; 6, basement tion, and increased by conditions, as 



cold to the surface, which diminish the 



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- 



