192 STUDENTS HISTOLOGY 



taining blood for capillaries. The human kidney is rarely abso- 

 lutely normal; and blood is frequently found outside the proper 

 channels. The vessels will be differentiated by the histology of 

 their walls. Quite a number of venules will be seen running in 

 groups in the medulla the venulce rectce. 



8. The same elements as in 7 (shown in a transverse section 

 of the middle of a Malpighian pyramid, Fig. 121). 



FIG. 121. TRANSVERSE SECTION OF PYRAMID OF MALPIGHI. SAME TISSUE AS 

 SHOWN IN FIG. 118. STAINED WITH H^EMATOXYLIN AND EOSIN (X400). 



A. Group of intertubular blood-vessels. 



B. Collecting straight tubules. 



C. Descending limb of Henle's loop. 



D. Ascending limb of Henle's loop. 



E. Principal collecting tubule. 



F. Principal tubule. Lower portion near the papillary duct. 



The ring of cells will be seen detached from the membrana propria in some instances. This 

 is due to contraction of the tissue during the hardening. 



In amphibians the epithelial cells at the neck of the capsule of 

 Bowman are ciliated. In man and the mammals the epithelial cells 

 of the convoluted, spiral, and irregular tubules and the ascending 

 limb of Henle's loop have distinct, vertical striations close to the 

 basement membrane. The cells of the convoluted tubules show 



