178 NORMAL HISTOLOGY. 



mounted in glycerin to which strong acetic acid has been 

 added in the proportion of i-ioo. 



Epithelium of the Air-vesicles. The lung of a freshly- 

 killed animal (a young cat is best) is filled with a solution 

 of silver nitrate 1-500, in the manner just described, and 

 after remaining for half an hour, the tube between the 

 funnel and the lungs should be lengthened to about six 

 or eight inches, so as to increase the pressure, and the 

 funnel filled with a mixture of equal parts of alcohol and 

 water. Under this increased pressure the silver solution 

 will be partially driven out through the pleura and re- 

 placed by the dilute alcohol. When this replacement is 

 partially accomplished the lung is placed entire in alcohol 

 of the same strength and exposed to the light. After a 

 few hours it may be cut into pieces and preserved in 

 strong alcohol. Sections are made from the surfaces 

 which have become brown, and mounted in glycerin 

 tinged with eosin. 



Injected Lung. From bits of human lung whose blood- 

 vessels have been injected with the blue gelatin mixture 

 through the pulmonary artery, sections, which need not 

 be very thin, are made, stained with eosin and mounted 

 in balsam. 



