264 THE AMERICAN MONTHLY [Sept. 



It is possible to isolate the epithelial cells, as follows : 

 Cut open, through the middle, a frog's kidney which has 

 been macerating for 24 hours in weak iodised serum. 

 With scissors remove a piece and agitate it in a drop of 

 picro-carmine. A crowd of perfectly isolated cells may 

 be thus obtained. 



Endotheliu'))!, of Boioinmi''s Capsule. — To demonstrate 

 this, impregnation by silver nitrate must be resorted to. 

 A rabbit is killed by cutting the medulla ; the belly is 

 opened and the artery and the emulgent vein with the 

 ureter are carefully isolated. Into the artery inject ar- 

 tificial serum (physiological solution of salt, as follows: 

 Water, 1000; common salt, 7 grms. 5), to expel the blood 

 without changing epithelium. We know that epithelium 

 and, in general, otlier parts, will live for sometime inar- 

 tificial serum. When the liquid, injected very gently, 

 returns colorless through the veiu, substitute for the se- 

 rum a stream of distilled water. The salt is rapidly ex- 

 pelled and, if we act with sufficient celerity, the water 

 will not change the epithelium. Then pass through the 

 kidney a stream of silver nitrate, 1 to 500. The organ 

 at once whitens at points ; a few minutes are enough for 



a sufficient impregnation End the operation 



by passing another stream of distilled water, tie the ar- 

 tery, vein and ureter ; suspend the kidney by the ureter 

 in about 300 grms. of alcohol at 90 °c. The alcohol rap- 

 idly coagulates the surface of the kidney ; the 



injected vessels, the capsule of Bowman, the cortical por- 

 tions of the systems of convoluted tubes no longer con- 

 tract, and the hardening progresses so regularly that in 

 24 hours thin regular sections may be cut of the medu- 

 lary and of the cortical substance. The sections 

 mounted in glycerine or in balsam show the vessels, the 

 glomerules. Bowman's capsules and the origin of the 

 convoluted tubes at once impregnated with the silver, 

 and distended as if they had been inflated. 



