1876 



HUMAN ANATOMY. 



the divisions in a more or less marked degree, the renal lobules of the aquatic mammals being 

 unusually distinct. In some mammals (rodents, insectivora) the entire kidney corresponds to a 

 single papilla, while in others (elephant, horse) no distinct papillae exist. 



Fig. 1597. 



On making a longitudinal section of the fresh kidney, from its convex border 

 through the sinus, the papillae will be seen to form the free apices of conical masses, 



the renal pyramids, the bases of which lie embedded within 

 the darker surrounding kidney-substance composing the outer 

 third of the organ. This peripheral zone, which appears darker 

 and granular in contrast to the lighter and striated renal pyra- 

 mids, constitutes the cortex; the medulla includes the conical 

 areas formed by the pyramids and partially occupies the inner 

 two-thirds of the thickness of the organ. The cortex contrib- 

 utes the bulk of the kidney, alone forming the entire surface, 

 including the lips of the hilum, and receiving and surrounding 

 the bases of the pyramids. The cortical tissue further pene- 

 trates for a variable distance between the pyramids, separating 

 the latter and in places gaining the sinus. These interpy- 

 ramidal extensions are the renal columns, or columns of Be? tin, 

 and consist of typical cortical substance. Since the branches 

 of the renal blood-vessels lie within the interlobular connective 

 tissue separating the primary divisions of the fcetal organ, these vessels never enter 

 the kidney by passing into the papillae, but always enter at the side of these. They 

 therefore sink into the renal substance within the areas occupied by the renal columns, 

 the surfaces of which directed towards the sinus are pitted by the vascular foramina. 

 Within the sinus the blood-vessels surround the calyces with coarse net-works, enter- 

 ing and emerging from the renal substance through the orifices encircling the papillae. 

 On close inspection, preferably with the aid of a hand-glass, it will be seen that 

 the cortex, including that within the renal columns, is not uniform, but is subdivided 

 by narrow striated bands, wedge-shaped 



Right kidney of new- 

 bom child, showing lobula- 

 tion of surface. 



in outline and lighter in color, mto 

 radially disjSosed darker and lighter 

 areas. The latter, consisting of groups 

 of parallel tubules, are known as the 

 medullary rays (pars radiata), since 

 they are apparently due to prolonga- 

 tions of the medullary tissue. The 

 darker tracts intervening between the 

 medullary rays form the labyriiith (pars 

 convoluta), and appear granular, owing 

 to the tortuous character of the com- 

 ponent tubules. The labyrinth is 

 studded with bright red points mark- 

 ing the position of the vascular tufts 

 or glomertdi, which are never present 

 within the medullary rays or the renal 

 pyramids, although found within the 

 columns of Bertin. 



On sectioning minutely injected 

 organs, it will be observed that the 

 larger radially coursing interlobular ar- 

 teries, on gaining the boundary zone 

 between the cortex and medulla, break 

 up into smaller branches, some of which 



Fig. 1598. 



Cortex 



Interlobar 



blood-vessel 



Medulla 



Column of 

 Bertin 



Calyx, 

 cut across 



Renal papilla 

 Renal pelvis 



—Calyx 



\ — Portion of 

 sinus 



Renal 

 papilla 



Ureter 



Longitudinal section of right kidney, showing relations of 

 pelvis and its divisions to renal substance and to sinus. 



pass directly towards the surface, while others change their direction and assume an 

 arched horizontal course, thus producing the impression of " arcades" at the base of 

 dhe pyramids. The terminal twigs — " end-arteries," since anastomoses are wanting 

 — run generally perpendicular to the exterior of the kidney and occupy the centre 

 of the tracts separating the medullary rays. The latter, therefore, are the axes of 



