GLANDS. 431 



nuclei. (See Plate LX. fig. 3.) Mr. Bowman considered 

 that epithelium was not constantly present in these bodies ; 

 and that, when it was so 3 it only lined that portion of them in 

 connection with the tubes. This statement arose in a mis- 

 apprehension of the real structure of the Malpighian body. 



Vascular Apparatus. 



The vessels of the kidney consist of the renal artery and 

 vein, also of a vein which may be called portal : we will first 

 trace the course of the artery. 



Renal Artery. The renal artery, after its entrance into the 

 substance of the kidney, divides into numerous branches, 

 some of them pass between the medullary cones, others tra- 

 verse these in sets : arrived at the cortical part of the kidney, 

 many undergo a further subdivision, and some, passing to- 

 wards the Malpighian dilatations, form in part, upon its ex- 

 ternal surface, the Malpighian tuft or plexus of vessels (see 

 Plate LIX.^s. 1. 5.) ; others continue onwards to the surface 

 of the kidney, and there terminate in capillaries. (See Plate 

 LIX. ficj. 2.) Such is a brief sketch of the course of the 

 renal artery. 



The branches of the renal artery take, through the cortical 

 part of the kidney, a straight and parallel course ; some of 

 these branches give off lesser vessels on each side, which pass 

 towards, and are expended upon the Malpighian dilatations, 

 as also is, ultimately, the terminations of the main vessels from 

 which the lesser ones proceeded. Others, again, of the larger 

 and parallel branches, in like manner give off Malpighian 

 twigs ; but their terminations, in place of being exhausted 

 upon the Malpighian dilatations, reach the surface, and there 

 form, with the branches of the renal vein, an interlobular 

 plexus. It is seldom that a branch of the artery reaches 

 the surface of the kidney, without first communicating with 

 the Malpighian dilatations. 



Renal Vein. The renal vein has two origins: one in the 

 capillaries on the surface of the kidney ; these capillaries, 

 uniting with those of the renal artery, form the plexus, which 



M M 



