244 THE MICROSCOPE. 



branches of the portal vein or in the capillaries, must ne- 

 cessarily compress the ducts and the secreting structure of 

 the liver which fill up the intervals between them. The 

 result of such a pressure would be to drive the bile towards 

 the large ducts and to promote its escape. Tepid water 

 was, therefore, injected into the portal vein. The liver 

 became greatly distended, and bile with much ductal 

 epithelium flowed by drops from the divided extremity of 

 the duct. The bile soon became thinner, owing to its 

 dilution with water, which permeated the intervening mem- 

 brane, and entered the ducts. These long, narrow, highly- 

 tortuous channels were thus effectually washed out from 

 the point where they commenced as tubes not more than 

 1 -300th of an inch in diameter, to their termination in the 

 common duct, and much of the thick layer of epithelium 

 lining their interior was washed out at the same time. 

 The water was removed by placing the liver in cloths with 

 sponges under pressure for twenty-four hours or longer. 

 All the vessels and the duct were then perfectly empty 

 and in a very favourable state for receiving injection. The 

 duct was first injected with a coloured material. Freshly 

 precipitated chromate of lead, white lead, vermilion, or 

 other colouring matter may be used, but for many reasons 

 to which I have alluded, the Prussian blue injection is the 

 one best adapted for this purpose. It is the only material 

 which furnishes good results when the injected prepara- 

 tions are required to be submitted to high magnifying 

 powers. Preparations injected in this manner should be 

 examined as transparent objects." 1 



Of Preparing Portions of Injected Preparations for Mi- 

 croscopical Examination. — When thin tissues, such as the 

 mucous membrane of the intestines or other parts, have 

 been injected, it is necessary to lay them perfectly flat 

 and wash the mucus and epithelium from the free sur- 

 face, either by forcing a current of water from the wash- 

 bottle, or by placing them in water and brushing the 

 surface gently with a camel's hair brush. Pieces of a 

 convenient size may then be removed and mounted in 

 a solution of naphtha and creosote, In. dilute alcohol, in 



(1) Dr. L. Beale, "On the Anatomy of the Liver of Man and Vertebrate 

 Animals." 



