THE KIDNEY. 



203 



twenty-four hours, afterward transferred to stronger alcohol, 

 then to absolute alcohol, and finally mounted in dammar or 

 balsam. Vertical sections show the arrangement represented 

 in Figs. 89 and 90 ; transverse sections, the appearance of 

 Fig. 92. 



The substance of the kidney is composed of secreting and 

 collecting tubules, vessels, and a stroma, which fills the inter- 



Fro. 90. Human kidney. Vertical section through cortical portion : A, pyramidal prolongation ; B, 

 cortical substance proper ; C, artery ; D, glomerulus. x 64. 



spaces between the tubules, and is more abundant in the med- 

 ullary than in the cortical substance. In human adults this 

 connective material is found in small quantity and is a sort of 

 colloid substance. In the lower animals it is more abundant, 

 and assumes the character of real connective tissue. In young 

 infants there is said to be a greater proportionate amount of 

 this tissue than in subsequent life. 



The renal tubules. The tubules are found both in the corti- 



