596 SPECIAL HISTOLOGY. 



ting parenchyma. To the former belong the adipose capsule, as it is 

 termed (capsula s. tunica adiposa), constituted of lax connective tissue 

 abounding in fat cells, scarcely deserving the name of a special mem- 

 brane, and the fibrous tunic (tunica propria s. albuginea), a thin but strong 

 coat, of a whitish color, composed of common connective tissue and 

 numerous fine elastic networks, which closely invests the kidney, and, at 

 the hilus, is in apposition with the pelvis of the gland and the vessels, 

 but does not penetrate into the interior of the organ. 



The secreting parenchyma, which is abruptly defined from the fibrous 

 membrane, consists, as seen by the naked eye, of two portions, the 

 medullary and the cortical substance, the former of which constitutes 8-15, 

 isolated, conical, masses converging towards the Jiilus, the pyramids of 

 Malpighi ; whilst the latter forms the entire cortical part of the organ, 

 and moreover, sends processes between the separate pyramids which 

 extend as far as the Jiilus, the columnce Bertini, and is apparently 

 continuous throughout the gland. Examined microscopically, however, 

 the cortical substance is found to be divided into as many segments as 

 there are pyramids, and the kidneys, therefore, may be regarded as made 

 up of a certain number of large, though closely connected lobes. 



187. Composition of the Renal Substance. Both portions of the Idd- 

 neys consist, essentially, of the uriniferous canals (tubuli uriniferi), 

 cylindrical tubules, measuring, on the average, 0'016-0*025 of a line. 

 They commence in each renal lobe or segment, in those portions of the 

 pyramids which are surrounded by the calices renales, or on the renal 

 papillae, by, on the average, from 200 to 500 orifices, O'024-O'l of a line 

 wide, scattered over the surface of those processes ; they traverse the 

 pyramids in nearly a straight line and in close contiguity, whence they 

 are termed in that situation, tubuli recti (or Belliniani) (Fig. 245 k). 

 In this course, each of the straight canals divides repeatedly, most usually 

 under very acute angles and at first with a considerable diminution of 

 size, either into two (Fig. 245 ?), or more rarely into three or four, so that, 

 ultimately, a complete bundle of finer tubules is produced from them ; and 

 in this way the continued increase in breadth of the pyramids towards 

 the exterior is accounted for. At the same time, towards the base of 

 the pyramids, the connection of the ducts of Bellini is rendered less 

 close, by the interpolation between them, at regular distances, of large 

 vascular bundles (arteriolce and venulce rectce), and they become sepa- 

 rated on all sides from each other, so that, in perpendicular sec- 

 tions, the pyramids (the papilla? of course excepted) in the entire 

 circumference appear to spread out into numerous small bundles or 

 pencils the pyramids of Ferrein of authors but which, as sections 

 across them show, are only to be regarded as separate, sharply-defined 

 fasciculi. The tubuli uriniferi, even here, assume a slightly undulating 



