526 



MANUAL OF HISTOLOGY. 



to ascertain the length of this very tortuous passage through which the 



urine must now. and, from the 

 calculations of Sclnceigger-Sei- 

 del, it would appear that, from 

 Bowman's capsule to the tip of 

 the papilla is about 26 mm. in 

 the Guinea pig, 35-40 in the 

 cat, and about 52 mm. in man. 

 Turning now to the susten- 

 tacular substance of these very 

 intricate glandular passages, we 

 find that it consists of a small 

 but by no means unvarying 

 amount of fibrous stroma 

 throughout the whole organ. 

 In the cortex it consists of par- 

 titions composed of connective- 

 tissue elements, with homoge- 

 neous or streaky intercellular 

 matter, which is somewhat more 

 abundant in the neighbour- 

 hood of the adventitial lamina 

 of the larger blood-vessels and 

 Bowman's capsules. At the 

 surface of the organ, also, this 

 stroma presents itself as loose 

 areolar tissue, and is continuous 

 here with the capsule of the 

 kidney. The sustentacular sub- 

 stance is somewhat firmer in 

 the medullary rays than else- 

 where. It appears to attain its 

 highest degree of development, 

 though this is always but of a 

 very low order, in the medul- 

 lary substance (fig. 521, e). It 

 may be well seen in sections of 

 kidneys hardened in alcohol or 

 chromic acid, the sections hav- 

 ing been well brushed out, and 

 by the aid of maceration in 

 hydrochloric acid the stellate 

 connective-tissue cells may be 

 isolated very clearly, as has 

 been shown by Schiceigger- 

 Seidd. 



Fig. 522. Plan of the circulation of the kidney (much 

 shortened). 1. External portion of cortex. 2. Cortex. 

 3. Boundary layer. 4. Medulla. 5. Apex of papilla, 

 a, arterial twig ; 6, vein ; c, vas afferens ; d, vas efferens ; 

 e, vas efferens and /, capillary network of the surface ; 

 g, the was efferens of a deeper-seated glomerulus; h, 

 arteriola recta ; t, venous radicle of the surface ; k, capil- 

 laries of the medullary process; I, of the convoluted 

 tubes; m, venul-ce rectos; n, medullary capillaries; o, 

 network around the openings of the uriniferous tubes. 



273. 



We have now to consider 

 the blood-vessels of the organ, 

 which exhibit considerable 

 peculiarity of arrangement. 

 As a rule both arterial and veinous trunks enter the human kidney at 



