RAPID PREPARATION OF SECTIONS FOR DIAGNOSIS. 431 



that are inevitable cause the glycerin to make its way between the 

 glass and cement, loosening the latter. 



A better medium than glycerin for sections that cannot be sub- 

 jected to the action of alcohol for the purpose of dehydration is 

 glycerin-jelly. This is prepared by soaking the best French gelatin 

 in cold water until it has imbibed all it will readily take up, then 

 melting the gelatin, after pouring off the excess of water, and 

 adding an equal bulk of glycerin. A little carbolic acid may be 

 added to the mixture to preserve it. The manipulations for mount- 

 ing are similar to those given above, the sections being transferred 

 from water to the slide. The glycerin-jelly may be melted and a 

 drop placed upon the section, or a little lump of the solid jelly may 

 be placed upon a cover-glass, melted by gentle heat, and the cover- 

 glass then inverted over the section on the slide. After the jelly 

 has dried at the edges of the cover-glass they may be painted with 

 xylol balsam, dammar, or some cement. 



The Rapid Preparation of Sections for Diagnosis. 



The most expeditious means of obtaining sections of fresh tis- 

 sues is to cut them without preliminary treatment with reagents, 

 either free hand with a razor, or with the aid of a freezing mi- 

 crotome (page 415). Such sections may be stained with methylene- 

 blue (aqueous solution, page 423), or they may be examined in 

 neutral salt solution. If they are to be stained, spread them out 

 on a slide, pour a few drops of the methylene-blue solution over 

 them, and, after a few moments, wash off the dye with water and 

 cover the section. If such rapid work is not necessary, the sections 

 can be fixed in formalin (page 416), and, after washing out that 

 reagent, stained. Such sections may be hardened and dehydrated, 

 by placing them in dishes of increasingly strong alcohols, and 

 finally mounted in dammar ; but the results are by no means so 

 good as when fixation and hardening are done before sections are cut. 



When time is not pressing the following method will give good 

 results : 



1 . Fix and harden pieces not over \ inch thick in absolute alcohol 

 on quick-lime over night (page 407). 



2. Dip the specimen in thick collodion and embed it on a glass 

 block by the rapid method (page 412). When the block has been in 

 80 per cent, alcohol for three or four hours it may be cut ; but it is 

 better to let the collodion harden for twenty-four hours. 



