ANATOMY OF THE KIDNEYS. 145 



aptly compared to a bean ; and the concavity, the deep, cen- 

 tral portion of which is called the hilum, looks inward 

 toward the spinal column. The weight of each kidney is 

 from four to six ounces, usually about half an ounce less in 

 the female than in the male. The left kidney is nearly 

 always a little heavier than the right. 



Outside of the proper coat of the kidney is a certain 

 amount of fatty tissue enclosed in a loose fibrous structure. 

 This is sometimes called the adipose capsule ; but the proper 

 coat consists of a close net- work of the ordinary white fibrous 

 tissue, interlaced with numerous small fibres of the elastic 

 variety. This coat is thin, smooth, and readily removed 

 from the surface of the organ. At the hilum it is continued 

 inward to line the pelvis of the kidney, covering the calices 

 and blood-vessels. This coat, however, is not continued into 

 the substance of the kidney. 



On making a longitudinal section of the kidney, it pre- 

 sents a cavity at the hilum, bounded internally by the dilated 

 origin of the ureter. This is called the pelvis. It is lined 

 by a smooth membrane, which is simply a continuation of 

 the proper coat of the kidney, and which forms little cylin- 

 ders, called calices, into which the apices of the pyramids are 

 received. Some of the calices receive the apex of a single 

 pyramid, while others are larger, and receive two or three. 

 The calices unite into three short, funnel-shaped tubes, called 

 infundibula, corresponding respectively to the superior, mid- 

 dle, and inferior portions of the kidney. These finally open 

 into the common cavity, or pelvis. The substance of the 

 kidney is composed of two distinctly-marked portions called 

 the cortical, and the medullary, or pyramidal. 



The cortical substance is reddish and granular, rather 

 softer than the pyramidal substance, and is about one-sixth 

 of an inch in thickness. This occupies the exterior of the 

 kidney, and sends little prolongations (columns of Bertin l ) 



1 BERTIK, Memoire pour servir d Fhistoire des reins. Memoires de F Academic 

 Royale des Sciences, annee, 1744, Paris, 1748, p. 77. 

 10 



