4iO 



VESSELS OF THE KIDNEY. 



[sect. 188. 



branches (o"o6'" to 0"i"'), which run directly outwards between the 

 cortical fasciculi, and may be most fitly called arterice interlobulares 

 (fig. lb"], a). It is these which support the Malpighian corpuscles, 

 and, apart from some twigs which pass to the envelope of the 

 organ, are entirely consumed in the formation of their vascular 

 coils. That is to say, each interlobular artery gives off, in its entire 

 length, and in two, three, or four directions, a large number of 

 fine twigs of arterial structure, with a diameter of o"Oo8'" to 0'02" ; 

 and these, after a short course, penetrate the envelope of a Mal- 

 pighian corpuscle, either directly or in several divisions, and 

 appear as the vasa afferentia of its vascular coil. Each of these 

 Fig. 170. vascular coils (figs. 169,170) 



consists of a dense convolution 

 of fine vessels, of o"oo4'" to 

 o - oo8" in diameter, having 

 the ordinary structure of ca- 

 pillaries (with structureless 

 wall and nuclei), and are pro- 

 vided with an efferent vessel 

 besides the entering artery. 

 The manner in which these 

 two vessels are connected with 

 each other is not that which 

 occurs between arteries and 

 veins, but resembles that which 

 is found in the so-called rete 

 mirabile, the vas afferens di- 

 viding, immediately after its 

 entrance, into five to eight 

 branches, and each of these, 

 again, into a tuft of capillaries. 

 These are twisted and wound 

 together in various ways, aud 

 pursue their course without 

 forming anastomoses. They at last re-unite to form a trunk, in 

 exactly the same manner as they themselves were formed. As a 

 rule, the two trunks of the glomerulus enter and pass out near to 

 each other, and opposite the origin of the tubule ; the finest vessels 

 of the coil (0-003'" to O'oo^."' in diameter) are invariably found 

 exactly at the spot where the urinary tubule commences. In 

 birds, amphibia, and fish, each glomerulus consists of one single 

 tortuous vessel. 



f 





From the human kidney, after Bowman, a. 

 Termination of an art. interlobularis ; 6. arterial 

 afferentes ; c. naked glomerulus ; d. vas effertns ; 

 e. glomeruli enveloped by the Malpighian cap- 

 sules; /. uriniferous tubules arising from the 

 same. Magnified 45 times. 



