STRUCTURE OF THE K1DXEY. 



443 



Fig. 123. 



some part of their course, or being continued from their 

 extremities at the bases of the pyramids, pass down loop- 

 wise in the pyramids for a longer or shorter distance, and 

 then, again turning up, end in the convoluted tubes whose 

 extremities are dilated into the Malpighian capsules before 

 referred to (fig. 122). On a transverse section of a pyramid 

 (fig. 123), these looped tubes are seen to be of much 

 smaller calibre than the straight ones, which are passing 

 down to open through the papilla. 



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 -j-^ of an inch. Each of them is com- 

 posed of the dilated extremity of an urinary tube, or 

 Malpighian capsule, enclosing a tuft of blood-vessels. 



In connection 

 with these little 

 bodies the gene- 

 ral distribution of 

 blood-vessels to 

 the kidney may be 

 here considered. 



The renal ar- 

 tery divides into 

 several branches, 

 which, passing 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 



* Fig. 123. Transverse section of a renal papilla (from Kolliker) ~. 

 a, larger tubes or papillary ducts ; 6, smaller tubes of Henle ; c, blood- 

 vessels, distinguished by their natter ^epithelium ; d, nuclei of the 

 stroma. 



