XXVIII.] KIDNEY. 3 1 i 



tween the straight tubules of the medulla. The medulla is not so 

 vascular as the cortex, and it has no glomeruli. 



5. Injected and Stained T.S. Kidney. A not too thin injected 

 section say injected with a blue mass may be stained with picro- 

 carraine, which makes the tubular structures more distinct by 

 staining their nuclei. 



6. Fresh Kidney Glomeruli and Basement Membranes of 

 Tubules. Expose a fresh kidney to the air for a day or two 

 according to the temperature. Cover it to prevent evaporation. 

 Tease part of the medulla and cortex in normal saline. 



(a.) (H) Observe the long, partly empty, structureless, basement 

 membranes of the tubules, often exhibiting folds ; 

 also isolated cells of the tubules. 



(b.) Isolated glomeruli, consisting of several 

 tufts of capillaries. The nuclei of their cells are 

 revealed by dilute acetic acid. 



(c.) Narrow tubules, not unlike blood-capil- 

 laries, but they possess a wall lined by a layer of 

 squames, the nucleated part of .the squames alter- 

 nating on opposite sides of the tubule. These are 

 the descending part of the looped tubule (fig. FIG. 3 oo. Part of De- 



scending Looped 

 n T i j. i /* n * ^ -^'0- , m -L , Tubule of Heule. 



7. Isolated Cells of the Different Tubules. 



Place very small pieces (size of a -split-pea) 24-48 hours in a 5 per 

 cent, solution of neutral ammonium chromate. Wash in water, and 

 tease small fragments in a 50 per cent, solution of potassic acetate, 

 or, without washing, tease a fragment in the 

 chromate solution. 



(a.) (H) Note specially the cells of the con- 

 voluted tubules and those of the ascending limb 

 of Henle's loop. They show the " rodded " char- 

 acter of the outer part of the protoplasm. Ad- 

 joining cells tend to interlock with each other 



(% 3 0- FIG. ooi.- Isolated 



8. Isolated Tubules. Place small pieces (size ceils from COM vo- 



c \ n ,i i j n . , ^ luted Tubules, i. 



or a pea) 01 the kidney ot a mouse, tortoise, or on the flat with 

 guinea-pig (3-4 hours) in pure hydrochloric acid cesses- C 2 "on e^ige 

 or 40 per cent, nitric acid (2-4 hours), wash in and '" i-odded." 

 water and leave them in water for 18-24 hours. ^ ui 

 They swell up, and their constituents readily fall 

 asunder. Place a fragment in water slightly tinged with iodine and 

 gently tap the glass slide, or stain with dilute acid-fuchsin. This 

 is sufficient to cause the tubules to fall asunder. 



(L and H) In a part from the cortex search for a convoluted 

 tubule still connected with its capsule, the twists on the tube itself, 



