102 THE KIDNEYS, BY C. LUDWIG. 



occurs in a radial manner, forming the venae stellatas. The 

 common trunk proceeding from the centre of a star runs into 

 that portion of the cortical region which contains glomeruli and 

 medullary rays, and there becomes applied to an arteria inter- 

 lobularis. The several veins thus originating run towards the 

 boundary of the medulla and cortex, receiving numerous and 

 variously sized branches which originate in the capillaries of 

 the cortical plexus. The veins are always so imbedded in the 

 cortex, that even when empty their orifices remain open. 



BLOODVESSELS OF THE MEDULLARY PORTION. The blood 

 flowing to the medullary portion of the kidney is, with but 

 slight exception, conveyed by long vessels termed the arterice 

 rectce, which collectively enter the medulla from the side of the 

 cortex (fig. 150, ar and ar'). The term arteries, in the fullest 

 sense of the word, is only applicable to a portion of them ; the 

 remainder, indeed, transmit their blood into the capillaries of 

 the medulla, but do not present either the structure of the 

 walls or the mode of distribution of arterial vessels. 



Those arteriolae rectce that from their structure and mode 

 of origin are clearly arterial in character, proceed from the 

 branches of the renal arteries, that also give off the arterias 

 interlobulares towards the cortex. The other portion of the 

 arteriolse rectse, that have no circular muscles in their wall, are 

 nothing but the very elongated vasa efferentia of those glome- 

 ruli which are in immediate proximity to the medulla. 



The whole of the arteriolse rectse, whatever may be their 

 origin, immediately run towards the fissure-like spaces in the 

 marginal portion of the medulla between the fasciculi of urinary 

 tubules. 



Many of the little trunklets, even before their entrance into 

 these spaces, divide into several branches, and having reached 

 them, continue to divide whilst pursuing their course towards 

 the papillae. In this manner a brush of parallel vessels arises 

 from the trunk of each arteriola recta ; and when the vessels 

 of this brush come into contact with the converging bundles 

 of the urinary tubules, they break up into capillaries that form 

 looped plexuses around the tubules. And as, on account of the 

 progressive narrowing of the fissure, one artery after another 



