202 



MANUAL OF HISTOLOGY. 



amount of blood in the kidney ; they are the MalpigJiian 

 bodies, or glomeruli (Fig. 89, E). 



The boundary layer ' is characterized by numerous blood- 

 vessels, some of which, unite to form an arcade (Fig. 89, C), 

 which is parallel to the convex surface of the kidney, and from 

 which branches are given off to the cortical substance proper. 



The renal artery, before it enters the 

 hilum of the kidney, divides into 

 branches, which pierce the medulla 

 between the pyramids and ascend 

 toward the cortical substance until 

 they reach the boundary layer. Here 

 they divide obliquely or at right 

 angles to give off smaller branches, 

 which have the direction and arched 

 ppearance above referred to (Fig. 

 89, C). These arched vessels then 

 send off the branches already men- 

 tioned, which traversing the centres 

 of the cortical substance proper, at 

 right angles to the parent stem (Fig. 

 89, D), extend almost to the capsule 

 of the kidney. On their way they in 

 turn give off smaller twigs, each of 

 which bears a glomerulus upon its 

 extremity (Fig. 89, E). In this way 

 there is an alternate arrangement of 

 pyramidal prolongation and cortical 

 substance proper (Fig. 90). Though 

 he pyramidal prolongations almost 

 reach the capsule of the kidney, 

 they never quite touch it, being sep- 

 arated by the interposition of some cortical substance proper 

 (Fig. 89). 



Specimens for study should be made from a fresh kidney, 

 in which the renal artery has been injected with carmine-gela- 

 tine, the whole organ having been subsequently immersed in 

 alcohol of 50 per cent, strength. When in that fluid it is to be 

 divided into four or more parts, allowed to remain therein for 



FIG. 89. Human kidney. Vertical 

 section through cortical and medullary 

 substances : A, branch of renal artery ; 

 B, vein, immediately beneath former, but 

 hardly visible in the figure; C, arched 

 arterial branches in the boundary layer ; 



D, artery of the cortical substance proper ; 



E, Malpighian bodies or glomeruli : F, 

 medullary rays or pyramidal prolonga- 

 tions ; G, vessels of the medulla, the vasa 

 recta, x 10. 



1 Henle: Grenzschicht, Eingeweidelehre. 



