THE KIDNEY 427 



the organ the capsule is continuous with the connective tissue which 

 envelops the renal pelvis, infundibula, and calyces, and which^m the 

 intervals between adjacent calyces, comes into relation with the cortical 

 substances of the renal columns. 



This connective tissue of the hilujn is of the^areolar variety and 

 contains much adiposQissue. It supports the large__arteries and veins 

 as they pass along the surface of the renal pelvis on their way to and 

 from the renal columns, where they enter or leave the parenchyma. 

 Sympathetic nerve fibers and a few small ganglia are also found in this 

 region. 



The connectj_ve_tissue of the interior of the organ, interstitial 

 is ver^jiscjyity, and in most parts consists only of isolated fibrils which 

 invest the blood-vessels and the renal tubules. It forms a very delicate 

 reticulumjjv which the walls of the uriniferous tubules are loosely ur'^ted 

 11 the epithelium of these tubules is removed, a ^ delicate fibrous network 

 remains pEhisnetwork incloses a homogeneous basement membrane upon 

 which the lining epithelium ordinarily rests. Elastic fibers scarcely 

 occur arn_ojijhejubules_ oj^ the kidney. The interstitial tissue is slightly 

 increased in amount afyout the larger blood-vessels, the renal corpuscles 

 of the cortex, and the femall blood-vessels of the boundary zone of the 

 medulla. At the apex ojf the renal pyramid it invests the large papillary 

 ducts in considerable quantity. 



THE URINIFEROUS OR EENAL TUBULES 



The urinif erous tubules begin in the cortical labyrinth as the capsules 

 pprpnsnTps. Assuming a tubular form they then pursue a 



tortuous course through the pars convoluta and filially enter the boundary 

 zone~ot~the medulla, where, much reduced in size, they form the loop of 

 Henle, which consists of a short, descending, thin limb, a U-shaped loofi, 

 ancTa long, ascending or thick limb. This last division, after recrossing 

 the boundary zone of the medulla, enters a pars radiata and returns 

 to the region of its origin, where it becomes again convoluted. A short 

 arched lultuJe connects this convoluted portion witli a straight collect UK/ 

 tubule of the cortical ray. The collecting tubules traverse the whole 

 length of the ray, uniting with their fellows and receiving other arched 

 tubules along their entire course. They then cross, the boundary zone 

 of the medulla, and finally, in the papillary zone, having meanwhile 

 received numerous accessions of straight collecting tubules, form the 



