XXV] KIDNEY 197 



blood vessels and descending limbs of the loops in 

 the midst of collecting tubes amongst which are also 

 limbs of the loops, in (c) the outflow tubes with large 

 lumina. 



4. Cut freehand a thin section of the inner part of the 

 cortex of a fresh kidney, tease it out in normal salt solution and 

 observe the appearance of the fresh cells in the isolated bits of 

 tubules. The convoluted tubes generally appear granular, the 

 ascending limbs striated, the outflow tubes transparent ; an 

 opaque deposit is sometimes present in a few of the outflow 

 tubes. 



5. Tease a small piece of the cortex of a kidney which has 

 ^een kept in 5 p.c. neutral ammonium chromate for 3 to 6 days. 



Observe the secreting cells of the tubes, isolated or in 

 groups, showing a very distinct striated outer portion ; in some 

 cells the outer part may appear as a brush of 'rods.' 



6. Section of kidney (taken as in 2) which 

 has been injected from the renal artery. Mount in 

 balsam. Observe 



The large arteries and veins in the outer part of 

 the intermediate layer. 



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 medulla and form a network throughout it; 

 the meshes are elongated in the direction of the tubes, 

 especially near the summit of the papilla. 



The interlobular arteries and veins running from 

 the larger vessels outwards in the cortex between the 

 medullary rays ; the arteries give off on all sides (two 

 rows will probably be seen in the section) small afferent 



