190 STUDENTS HISTOLOGY 



selected containing considerable blood, and the corpuscular ele- 

 ments have their color preserved [as in bichromate hardening] , the 

 vessels will be easily demonstrated.) 



5. Ascending limb of Henle's loops in the cortical labyrinths. 

 (The general course of these tubules is confined to the pyramids 

 of Malpighi and Ferrein; but occasionally one of them may be 

 seen passing in a tortuous course toward the outer cortex, running 

 between the proximal convoluted elements. They are easily recog- 

 nized by their small size and relatively large lumen. They are 

 lined with short columnar or cuboid cells, which stain deeply 

 blue with the haematoxylin . ) 



G. The pyramids of Ferrein. 



a. Collecting tubes. (These will generally be 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 like pavement epithelium when they 

 are seen from above or below. Endeavor to find a tube split 

 through the center longitudinally, and note the typical columnar 

 cells, as they project inward from the membrana propria toward 

 the now open lumen.) 



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

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

 color. The cells, however, plainly columnar, are large and hexag- 

 onal in transverse section. The lumen is small.) 



c. Ascending limbs of Henle's loop. (These are small tubes, 

 and have already been described. ) 



d. The intertubular capillaries. (Inasmuch as, in the speci- 

 men under consideration, the vessels of the pyramids are mostly in 

 tran verse section, they are not readily made out, especially if the 

 blood-corpuscles have become decolorized. 



7. Elements of the medullary portion. Fig. 120. 



a. Collecting tubes. (These tubes constitute a large propor- 

 tion of the medulla of the organ. They have already been 

 described. As the apex of the Malpighian pyramid is approached, 

 and the straight tubules unite to form the principal collecting 

 tubes, these again uniting to form the papillary ducts, the lining 

 cells will be seen to get shorter and the lumina larger. ) 



6 Spiral tubes. (These can, in many instances, be followed 

 down from the pyramids of Ferrein; and examples are frequently 

 seen very near the pelvis of the kidney in the cortical columns.) 



c. Descending limbs of Henle's loop. (These tubes are the 



