

4°4 



STRUCTURE OF THE KIDNEY. 



[sect, i 86. 



cortex is seen to divide into the same number of segments as 



there are pyramids present ; and the kidney, accordingly, may be 



Fig. 167. regarded as formed of a number of 



large lobes, intimately connected 



mSj together. 



§ 1 86. Composition of the Renal 

 Substance. Both portions of the 

 kidney consist essentially of the 

 urinary canaliculi, tubuli uriniferi, 

 cylindrical tubules, measuring, on an 

 average, o , oi6'" to 0*025'" * n di- 

 ameter. They commence in every 

 renal lobe or segment, at the renal 

 papillae, the part of the pyramids 

 enclosed by the calyces. Their open- 

 ings measure 0024'" to o'l"' in di- 

 ameter, and are scattered to the 

 number of from 200 to 500 upou the 

 surface of the papillae. Thence the 

 tubules extend into the pyramids, in a 

 direction mostly straight and paral- 

 lel, and are hence called tubuli recti 

 (or tubuli Belliniani) (fig. 166 k). 

 During this course, each of these 

 straight tubules repeatedly divides, 

 mostly at acute angles, .and, at first, 

 with considerable decrease in calibre. 

 The division is almost always into 

 two (fig. 166 I), more rarely into 

 three or four. In this manner, at 

 last, an entire fasciculus of fine tu- 

 bules arises from a 

 single main tubule, 

 and this explains the 

 constantly increasing 

 breadth of the pyra- 

 mids, as they are traced 

 from the papillae. At 

 the same time, the con- 

 nection of the straight 

 tubules becomes looser towards the bases of the pyramids, on 



Perpendicular section through a part of a pyramid, and of 

 the appertaining cortical substance of an injected kidney of a 

 rabbit. Half diagrammatical figure ; magnified 30 times. On 

 the left, the vessels ; on the right, the course of the urinary 

 tubules is represented, a. arteriss interlobulares with the 

 glomeruli Malpighiani, b. and their vasa afferenlia; c. vasa 

 effcrentia ; d. capillaries of the cortex ; e. vasa efferentia of the 

 outermost corpuscles passing into the capillaries of the surface of 

 the kidney ; /. vasa efferentia of the innermost glomeruli con- 

 tinuing in to the arteriolferectie, <7#<7 ; h. capillaries of the pyra- 

 mids forming from the latter ; i. a venula recta commencing 

 at the papilla; k. commencement of a straight urinary tubule 

 at the papilla; I. divisions of the same; m. convoluted tu- 

 bules in the cortex, not represented in their entire course ; 

 n. the same on the surface of the kidney ; o. continuation of 

 the same into the straight tubules of the cortex ; p. connection 

 of the same with the Malpighian capsules. 



