44 NORMAL HISTOLOGY. 



cised, all pulling or stretching of the part being avoided, 

 since this distorts the cells. It is now immersed in a 

 small quantity of one-half-per-cent. solution of gold 

 chloride. Here it remains for half an hour, when it is 

 removed, washed with pure water, and put into a few 

 cubic centimetres of the following mixture, known as the 

 reducing fluid : 



Amyl alcohol ..... I 

 Formic acid .... I 



Water ...... 100 



After remaining for twenty-four hours in the reducing 

 fluid, the specimen will probably have assumed a rich 

 violet color ; if not, it should be kept for twenty-four 

 hours longer in a fresh portion of the fluid. When the 

 requisite color has been obtained, the specimen is hard- 

 ened for a day in alcohol, embedded in hardened liver 

 or wax, and thin cross-sections made from it. The 

 sections are now stained lightly with haematoxylin, and 

 mounted in glycerin. They should be kept as much as 

 possible from the light, which, after a time, destroys 

 gold preparations. This method of staining with gold is 

 known as Pritchard's method. 



The epithelium on both the anterior and posterior 

 surfaces is now scraped off, and with a little care the 

 part may be divided into several thin layers by means 

 of fine forceps. These layers are lightly stained with 

 hsematoxylin and mounted in glycerin. 



In a specimen thus prepared, the basement substance 

 looks homogeneous or delicately striated ; fine nerve- 

 fibres are seen stretching across the specimen in various 



