SECT. 188.] 



VESSELS OF THE KIDNEY. 



4 II 



The vasa ejferentia, although arising from capillaries, are still not 

 veins, but have the signification, and, in part, the structure, of small 

 arteries. These, in their further course, break up into the capillary 

 network of the kidney, both in the cortex and pyramids, presenting 

 a somewhat different character at the two places. In the cortex 

 (fig. 167,^), the vasa ejferentia, 0-004'" to o - oo8'" in thickness, 

 break up, after a short course, into a very close network of capil- 

 laries (o , o02'", O'oo^" to o - oo6"' in diameter, with roundish, an- 

 gular meshes, 0005'" to 0-015'" wide), which surrounds the tortuous 

 tubules on all sides, and ma) r be regarded as continuous throughout 

 the whole cortical substance. It is only the efferent vessels of 

 those glomeruli which border inime- Fig. 171. 



diately upon the Malpighian pyramids 

 which form an exception to this con- 

 dition. These are not distributed to 

 the cortex, but to the pyramid; they 

 are uniformlv characterised bv their 

 more considerable diameter (o - oi'" to 

 00 1 6'"), their extended course, and the 

 scanty amount of their ramification. 

 These, which, with Arnold, I will call 

 arteriolce recta, penetrate into the whole 

 circumference of the pyramids, directly 

 between the Bellinian tubules, run 

 downwards towards the papilla?, at the 

 same time dividing repeatedly at acute 

 angles, and gradually become attenuated 

 to 0-004'" t° O'Oi'" in diameter. At 

 last, these straight arteries pass into 

 capillaries (o"003'" to 0-004"'), both in 

 the papillae and in the interior of the 

 pyramids. These capillaries are con- 

 tinuous with those of the cortex at the 

 margin of the pyramids, but are dis- 

 tinguished from them by their smaller 

 numbers and the elongated form of 

 their meshes. The renal veins commence at two places, viz., at 

 the surface of the organ and at the apices of the papillae. The 

 former are the veins of the cortex, and begin by small venous 

 radicles, collecting the blood from the outermost portion of the 

 capillary network. These small veins surround each separate 



Glomerulus, from the innermost 

 part of the cortex of the kidney of the 

 horse, after Bowman, a. art. inter- 

 lobularis; af. vas afferens; mm. glo- 

 merulus ; ef. vas efferens sive arte- 

 riola recta • b. division of the same in 

 the medullary substance. Magnified 

 70 times. 



cortical fasciculus in a 



regular 



manner, and unite in a stellate 



