THE KIDNEY AND URINARY PASSAGES. 



165 



of the tube which descends from the convoluted cortical por- 

 tion, and the side of the loop which passes off from this, the 

 name of the descending, and that portion which returns 

 towards the surface of the organ the name of the ascending 

 side. The former usually has the least, and the latter the 

 greatest diameter. The number of the looped canals in- 

 creases in proportion as we examine the cortical layer further 

 upwards towards the medullary layer. 



The terminal trunk of the efferent canal-work is invested 

 by the connective-tissue frame-work of the papillary apices, 

 and is without a membrana propria. The latter gradually 

 makes its appearance at the system of branches, and is more 

 distinct as well as more compact at the looped canals. Low 

 cylinder cells of 0.03 to 0.02 

 mm. border the transverse 

 section of the efferent canal 

 system (Fig. \$2,a). In the 

 further system of branches 

 the lining cells are still lower 

 (down to 0.016 mm.) 



Let us now, for an instant, 

 leave the efferent apparatus 

 and examine the secretory 

 portion of the kidney. 



We will now turn to the 

 cortical layer of our organ 

 and, first of all, examine more 

 closely the so-called cortical 



pyramids (Fig. 150, e). In their axis is seen a branch of the 

 renal artery, to which the glomeruli are attached by lateral 

 branches, like the berries on the stem of the grape (Fig. 

 150, e\ Fig. 155). 



A cortical pyramid, however — we repeat what was pre- 

 viously said — consists, for the rest, entirely of convoluted 

 uriniferous canals. They take their origin with a balloon- 

 shaped portion which surrounds the glomerules, as a bag does 

 a sponge. This is the Miiller's or Bowman's capsule. Its con- 



Fig. 152. — Transverse section through a re- 

 nal pyramid of the new-born child ; a, collec- 

 tive tubes with cylindrical epithelium ; b, de- 

 scending side of the looped canal with flat 

 cells ; c, returning side of the loop with granu- 

 lar celU ; d, transverse sections of vessels ; e, 

 connective-tissue frame-work substance. 



