PHYSIOLOGICAL ANATOMY OF THE KIDNEYS 



323 



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, middle and inferior portions of the kidney. 

 These finally open into the common cavity, the pelvis. The substance 

 of the kidney is composed of two distinct portions, called respectively 

 the cortical substance and the medullary, or pyramidal substance. 



The cortical substance is reddish 

 and granular, rather softer than the 

 pyramidal substance, and is about 

 one-sixth of an inch (4.2 millimeters) 

 in thickness. This occupies the ex- 

 terior of the kidney and sends little 

 prolongations, called the columns 

 of Bertin, between the pyramids. 

 The surface of the kidney is marked 

 by little polygonal divisions, giving 

 it a lobulated appearance. This, 

 however, is due mainly to the ar- 

 rangement of the superficial blood- 

 vessels. The medullary substance 

 is arranged in the form of pyramids, 

 sometimes called the pyramids of 

 Malpighi, twelve, fifteen or eighteen 

 in number, their bases presenting 

 toward the cortical substance and 

 their apices being received into the 



i . .-, , . -r^ . , Fig. 70. Longitudinal section of the kidney 



calices, at the pelvis. Ferrem sub- (Sa Ppey ). 



divided the pyramids of Malpighi i, i, 2| 2, 3 , 3 , 3 , 4l 4> 4 , 4t pyramids of Mai- 



into smaller pyramids, called the pighi , : ** s-s,s,s, apices of the pyramids, sur- 



"> rounded by the calices; 6, 6, columns of Berlin; 



pyramids of Ferrein, each Contain- 7, P elvis of the kidney ; 8, u PP er extremity of the 



ing about one hundred tubes radiat- 

 ing from the openings at the apices of the pyramids toward their bases. 

 The tubes composing these pyramids pass into the cortical substance, 

 forming corresponding pyramids of convoluted tubes, thus dividing this 

 portion of the kidney into lobules more or less distinct. 



The medullary substance is firm, of a darker red color than the 

 cortical substance, and is marked by tolerably distinct striae that take 

 a nearly straight course from the bases to the apices of the pyramids. 

 As these striae indicate the direction of the tubes that constitute the 

 greatest part of the medullary substance, this is sometimes called the 

 tubular portion of the kidney. 



