THE MICROSCOPE. 101 



of the rabbit or pig may be injected with little trouble from the 

 renal artery. Prussian blue or carmine will give good results if 

 only the injection be continued for some time in order that all the 

 capillaries of the glomeruli may be completely filled. The vein 

 may be injected at the same time. After the injection the organ 

 should be cut into eight or ten pieces, placed in Mtiller's fluid, and 

 in two or three weeks transferred to alcohol, to complete the 

 hardening. The sections should be cleared in oil of cloves, and 

 mounted in dammar. If desired, they can be slightly stained in 

 haematoxylin before clearing. 



It is quite difficult to inject the kidney from the ureter, and if 

 the injection be a success, the specimen will not show to any great 

 advantage; for owing to the convoluted course of the canals and 

 their dense arrangement, it is quite impossible to trace the course 

 of one tube for any considerable extent. The tubes may be sepa- 

 rated by teasing, if the interstitial connective tissue be previously 

 destroyed. 



This may be accomplished in a measure by boiling in acids, or 

 by macerating the section for 12 to 14 hours in muriatic acid, to 

 which has been added water till the acid has ceased to smoke. It 

 is then washed and placed in distilled water for a day, when the 

 tubes may be isolated by careful teasing. For isolating the tubes 

 the following method of Henle's is quite successful: Sections of 

 fresh kidney are placed in a flask partly filled with a mixture of 

 eight parts of common alcohol and two parts hydrochloric acid. 

 The cork of the flask is pierced with a long glass tube. The speci- 

 men is boiled in this mixture for several hours, when the fluid is 

 poured off and distilled water added. After seven or ten days, the 

 pieces can be carefully teased with needles. 



The epithelium of the tubes is best studied in the kidney of the 

 mature foetus. Small pieces are placed in a one per cent, solution 

 of potassic bichromate for two weeks. Thin sections are washed in 

 water, and slowly stained with carmine. 



LIVER. 



The usual methods are followed in studying this organ, viz.: 

 injecting, hardening and staining. To examine the uninjected 

 liver, small pieces are placed at once in Muller fluid and allowed 

 to remain there for two weeks, at least. A large amount of the 



