PHYSIOLOGICAL ANATOMY OF THE KIDNEYS. 



359 



fibrous tissue, interlaced with small elastic fibres. This coat is thin and 

 smooth and may be 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. 



The kidney in a vertical section presents a cavity at the hilum, which is 

 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 cylinders, 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 re- 

 ceive 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, 

 or pelvis. The substance of the kid- 

 ney is composed of two distinctly 

 marked portions, called the cortical 

 substance, and the medullary, or py- 

 ramidal substance. 



The cortical substance is reddish 

 and granular, rather softer than the 

 pyramidal substance, and is about one- 

 sixth of an inch (4*2 mm.) in thick- 

 ness. This occupies the exterior of 

 the kidney and sends little prolonga- 

 tions, called the columns of Bertin, be- 

 tween the pyramids. The surface of 

 the kidney is marked by little, poly- 

 gonal divisions, giving it a lobulated 

 appearance. This, however, is mainly 

 due to the arrangement of the super- 

 ficial blood-vessels. The medullary 

 substance is arranged in the form of 

 pyramids, sometimes called the pyra- 

 mids of Malpighi, twelve, fifteen or 

 eighteen in number, their bases pre- 



3 * 



sen ting toward the cortical substance, i, i, 2, 2, 3, 3, 3, 4, 4, 4, 4, pyramids of 



and their apices being received into 



the calices, at the pelvis. Ferrein sub- 



divided the pyramids of Malpighi into 



smaller pyramids, called the pyramids of Ferrein, each formed by about one 



hundred tubes radiating from the openings at the summit of the pyramids, 



toward their bases. The tubes composing these pyramids pass into the cor- 



tical 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, which take a nearly 



FIG. 113. Vertical section of the kidney (Sappey). 



8 ' upper extremi ' 



