132 PRACTICAL MICROSCOPY. 



(a) Collecting tubes. (These will be generally recognized by 

 their large size and the blue color of the staining. They are lined 

 with columnar cells, which are hexagonal in transverse section; and 

 this gives an appearance of pavement epithelium,, when they are seen 

 from above or below. Endeavor to find a tube split through the cen- 

 tre longitudinally and note the typical columnar cells, as they pro- 

 ject inward from the membrana propria, toward the now open lumen.) 



(V) The spiral tubules. (These resemble somewhat the convo- 

 luted tubules, especially as their cells take much the same dirty red 



Fio. 90. MEDULLARY PORTION OF SPECIMEN SHOWN IN FIG. 88. X 400. 



A. Collecting tubule in L. S. 



B. Collecting tubule from above, showing attached bases of lining cells. 



C. Collecting tubule presenting different appearance of lining cells, according to mode of 

 section. 



D. Ascending limb of Henle's loop. 



E. Same as last. The upper end of the tubule not sectioned. 



F. Descending limb of Henle's loop. Below may be seen the loop and ascending limb. 

 Gr. Oblique section of large collecting tubule. 



H. Basal, attached extremities of cells lining a large collecting tubule. 

 I. Intertubular capillaries. 



color. The cells however, plainly columnar, are large and hexagonal 

 in transverse section. The lumen is small.) 



