THE VBINARY APPARATUS. 



571 



which enter with them into the organ. (Some authors— among them Leyh— 

 describe, in addition to this capsula propria, a thin layer formed by the condensed 

 areolar matrix of the kidney, from which it can be easily torn.) 



Proper Tissue. — The glandular tissue of the kidneys {areola parmchijma, or 

 matrix) has, "externally, a reddish-brown colour, more or less deep in different 

 individuals. It is dense and friable, and easily torn when deprived of its fibrous 

 capsule. Its substance is not everywhere homogeneous : very dark-coloured 

 externally, where it forms the cortical layer, it becomes whiter around the pelvis, 

 where it constitutes the medullary layer ; where the latter comes in contact with 

 the former, and sometimes even near the pelvis, it assumes a tint like that of 

 wine. 



These two portions are not well defined, but penetrate each other reciprocally, 

 so as to compose, at their point of junction, irregular festoons, very readily per- 

 ceived in a horizontal section of the kidney (Fig. 339). 



The cortical is also distinguished from the medullary substance by its granular 



Fig. 339. 



HORIZONTAL LOXGITUDINAL SECTIOX OF THE HORSE'S KIDNEY. 



a. Cortical (or vascular) portion ; b, medullary (or tubular) portion ; c, peripheral portion of the 

 latter ; d, interior of the pelvis ; d', d', arms of the pelvis ; e, border of the crest ; /, infundi- 

 bulum : a, ureter. 



aspect, and the presence of minute, reddish spheres, readily visible to the naked 

 eye, and named Malpighian corpuscles ; while the medullary substance appears to 

 be composed of radiating fibres. 



In the Horse, the tissue of the kidney cannot be divided into lobules or 

 pyramids ; to the naked eye it appears to be composed of fibres that start from 

 every part of its exterior, and converge towards the crest of the pelvis. A micro- 

 scopical examination demonstrates these fibres to be canals or tubes ; hence they 

 are designated tuhuU uriniferi, or Bellini's tubes. A delicate connective tissue — a 

 kind of stroma, which is very rare in the cortical, but more abundant in the 

 medullary substance, especially in the vicinity of the pelvis — sustains the vessels 

 and nerves, and unites the tubuh uriniferi to each other. 



The tuhuli uriniferi are constituted by a proper amorphous membrane, very 



