XXII.] STRUCTURE OF THE KIDNEY. 233 



5. Cut similar sections through the outer part of 

 the medulla and observe the cross sections of 

 the tubes, and their membrana propria, with a 

 small amount of connective tissue between them; 

 sections of both the ascending and descending 

 limb of the loops of Henle will also be seen. 



6. Place a small piece of the cortex of a fresh 

 kidney in 5 p.c. neutral ammonium chromate, 

 tease out a fragment in the same fluid. 

 Observe the cells of the convoluted tubes, isolated 

 or in groups, shewing a very distinct striated 

 outer portion ; in some cells the outer part may 

 appear as a brush of ' rods/ 



7. Cut as thin a section as possible of the inner 

 part of the cortex of a fresh kidney, tease it out 

 in normal salt solution and observe the appear- 

 ance of the fresh cells in the isolated bits of 

 tubules. 



8. Take a piece of kidney which has been injected 

 from the renal artery, prepare sections like those 

 of ( 2), clear and mount in Canada balsam. 

 Observe 



a. The large arteries and veins in the upper part 

 of the intermediate layer. 



b. The small arteries and veins (arteriae et 

 venae rectae) given off from these, running 

 down between the medullary rays into the 

 medulla ; they break up almost immediately 

 into a brush of capillaries which enter the 



