THE KIDNEY 179 



Into the summit of each capsule, a small vessel (Figs. 52 

 and 53, v.a), one of the ultimate branches of the renal 

 artery, which reaches the kidney at the concave side, 

 with the ureters, and divides into branches which pass in 

 between the pyramids (Fig. 51, RA), enters (driving the 

 thin wall of the capsule before it), and immediately breaks 

 up into a bunch of looped capillaries, called a glomer- 

 ulus (Fig. 52 gl), which nearly fills the cavity of the 

 capsule. The blood is carried away from this glomerulus 



Fig. 52.— a Malpighian Capsule (highi.y magnified). 



v.a, small branch of renal artery entering the capsule, breaking up into 

 the glomerulus, r/.l, and finally joining again to form the vein, t:e. 



c, the tubule ; n, the epitheUum over the glomerulus ; b, the epi- 

 thelium lining the ciipsule. 



by a small vein or vessel (re), which does not, at once, 

 join with other veins into a larger venous trunk, but opens 

 into the network of capillaries (Fig. 53) which surrounds 

 the tubule, thus repeating the portal circulation on a 

 small scale. 



The course of the tubules is devious and peculiar. 

 After leaving the capsule each tubule becomes twisted 

 and is spoken of as convoluted (Fig. 54, II.). Passing 

 towards the medulla, at first in a slightly spiral course, 

 it proceeds straight down into the pyramid, where it bends 



N 2 



