352 THE KIDNEYS AND THEIR SECRETION. 



are seen to be of much smaller calibre than the straight ones, 

 which are passing down to open through the papillse. 



The Malpighian bodies are found only in the cortical part of 

 the kidney. 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 T ^ a of 

 an inch. Each of them is composed of the dilated extremity 

 of a urinary tube, or Malpighian capsule, inclosing a tuft of 

 bloodvessels. 



In connection with these little bodies the general distribu- 

 tion of bloodvessels to the kidney may be here considered. 



The renal artery divides into several branches, which, pass- 

 ing in at the hilus of the kidney, and covered by a fine sheath 

 of areolar tissue derived from the capsule, enter the substance 

 of the organ chiefly in the intervals between the papillse, and 

 penetrate the cortical substance, where this dips down between 

 the bases of the pyramids. Here they form a tolerably dense 



FIG. 123. 



Transverse section of a renal papilla (from Kolhker) -y^- a, larger tubes or papil- 

 lary ducts ; b, smaller tubes of Henle ; c, bloodvessels, distinguished by their natter 

 epithelium , d, nuclei of the stroma. 



plexus of an arched form, and from this are given off smaller 

 arteries which ultimately supply the Malpighian bodies. 



The small afferent artery (Fig. 124), which enters the Mal- 

 pighian body by perforating the capsule, breaks up in the in- 

 terior into a dense and convoluted and looped capillary plexus, 

 which is ultimately gathered up again into a single small effer- 



