338 



THE URINARY SYSTEM 



portions, oT^labyrinth proper, which include that portion of the 

 labyrinth which invests the medullary rays, and which, in sections 

 cut parallel to these columns (longitudinal sections) appears as a 

 portion of cortex inserted between the adjacent medullary rays ; 

 3, a narrow boundary zone of the cortex, " cortex corticis" of Hyrtl, 

 which is included between the fibrous capsule of the organ and 



the tips of the medul- 

 lary rays, and in which 

 10 the Malpighian bodies, 

 though present, are rela- 

 tively few in number. 



The Renal Lobule. 

 In fetal and infantile life 

 the kidney is distinctly 

 lobulated. This condition 

 is permanent in some ani- 

 mals, each lobe consisting 

 of a Malpighian pyramid 

 with its related portion of 

 cortical substance. In man, 

 after the first year, the renal 

 lobes completely fuse and 

 eventually leave scarcely a 

 trace of the early lobar con- 

 dition. 



The term renal lobule or 



a \ \\\\\iiuiiiii///y reniculus, as applied to the 



adult human kidney, refers 

 to a still smaller subdivi- 

 sion of the organ, one which 

 includes a single medul- 

 lary ray together with that 



medulla ; c, cortex ; 1, apex of a Malpighian pyra- portion of the Cortical laby- 



mid ; #, capsule ; <?, tubules of the medulla ; 4, vasa pinth by which it IS im- 

 rectse; <5, vascular arcades; 6, a medullary ray; , . , . m , . 



7, labyrinth ; 8, interlobular artery ; 9, Malpighian mediately invested. This 



body ; 10, " cortex corticis." (After Testut.) lobule is the anatomical 



unit of the kidney and is 



thus comparable to the hepatic or pulmonary lobule. The tor- 

 tuous secreting portions of its uriniferous tubules are contained 

 in the labyrinth at the periphery of the lobule, while its straight 

 conducting portions lie in the medullary ray in the axis of the 



FIG. 279. DIAGRAM OF THE STRUCTURE OF THE 

 KIDNEY. 



a, papillary zone, and 5, boundary zone of the 



