426 



EXCRETION 



vessels, the vasa recta, in the pyramids between the tubes. Some of these 

 are branches of the vasa efferentia from Malpighian bodies, and therefore 

 comparable to the venous plexus around the tubules in the cortical portion, 

 while others arise directly as small branches of the renal arteries. 



FIG. 290. Malpighian Capsule and Tuft of Capillaries, Injected through the Renal 

 Artery with Colored Gelatin, a, Glomerular vessels; b, capsule; c, anterior capsule; d, 

 glomerular artery; e, efferent veins;/, epithelium of tubes. (Cadiat.) 



FIG. 291. Diagrams Illustrating Stages in the Development of the Malpighian Cap- 

 sule. In i and 2 the developing blood vessel is approaching the blind end of the capsule. 

 In 3 the tubule is beginning to invaginate and enclose the capillary. In 4 and 5 later 

 stages are shown. The cells forming the two layers of the capsule grow very thin. (Bailey.) 



Renal Nerves. Vaso-constrictor and vaso-dilator nerves are sup- 

 plied to the blood vessels of the kidney, but no clearly denned secretory 

 nerves have yet been demonstrated for the organ. The vascular nerves 

 arise out of the anterior spinal roots (Bradford), chiefly the eleventh to the 



