EXCRETION. 



465 



Blood-Vessels. 



Blood-supply. In connection with the general distribution of blood- 

 vessels to the kidney, the Malpighian Corpuscles must be further con- 

 sidered. They (fig. 293) are found only in the cortical part of the kid- 

 ney, and are confined to the central 

 part, which, however, makes up about 

 seven -eighths of the whole cortex. 

 On a section of the organ, some of 

 them are just visible to the naked 

 eye as minute red points; others are 

 too small to be thus seen. Their 

 average diameter is about -j^-g- of an 

 inch (-J- mm.). Each of them is com- 

 posed, as we have seen above, of the 

 dilated extremity of an uriniferous 

 tube, or Malpighian capsule, which 

 encloses a tuft of blood-vessels. 



The renal artery divides into sev- 

 eral branches, which, passing in at 

 the hilus of the kidney, and covered 

 by a fine sheath of areolar tissue de- 

 rived from the capsule, enter the sub- 

 stance of the organ chiefly in the in- 

 tervals between the papillae, and at the 

 junction between the cortex and the 

 boundary layer. The main branches 

 then pass almost horizontally, form- 

 ing more or less complete arches and 

 giving off branches upward to the 

 cortex and downward to the medulla. 

 The former are for the most part 

 straight; they pass almost vertically 



tViP kirlnpv <n* vino- 

 ttie Kidney, giving 



i,,4.^n11-r T i-n Q ll rHrcmfirmc Inno-or 

 , laterally in ail directions longer 



x;/, capillaries of medulla; g, venous ^ l irkr f aT . hranohpi whioh nlH. 

 ; 7i, straight veins of medulla; j, vena stel- and Shorter DranCI .68, WHJ 



mately supply the Malpighian bodies. 

 The small afferent artery (figs. 293 and 294) which enters the Malpig- 

 hian corpuscle, breaks up in the interior as before mentioned into a 

 dense convoluted and looped capillary plexus, which is ultimately gath- 

 ered up again into several small efferent vessels, comparable to minute 

 veins, which leave the capsule at one or more places near the point at 

 3 



/ 



Fig. 292.~Vascular supply of kidney, o, , XT,, onyfo^o 

 part of arterial arch; 6, interlbbular artery ; c, to the SUrlaCC 

 glomerulus; d, efferent vessels passing to the 

 medulla as false arteria recta; e, capillaries of 

 cortex 

 arch 

 lula; z, inteiiobular vein. (Cadiat.) 



