THE PREPARATION OF MICROSCOPICAL OBJECTS 7 



preparations it is better to use glycerine jelly ; a drop of this 

 should be melted on the slide, and the object transferred to it 

 from glycerine : ring with cement as before. 



3. Canada Balsam is the most generally useful medium for 

 permanent preparations, as requiring no cement. Specimens 

 that are to be mounted in balsam must first be deprived of all 

 water they may contain by placing for an hour or so in absolute 

 alcohol, and should then, before mounting, be soaked for a few 

 minutes in oil of cloves or turpentine in order to clear them, 

 i.e., render them permeable by the balsam. Canada balsam, if 

 too ,thick, may be diluted with chloroform, turpentine, or 

 benzole. 



B. Teasing. 



The object of teasing is to separate the several parts of a 

 tissue or organ from one another in order to show their minute 

 structure. 



The fragment to be teased should be placed on a slide in a 

 drop of the medium in which it is to be mounted, and then 

 torn up into shreds by means of a couple of needles held one 

 in each hand. The process is often greatly facilitated by 

 placing the slide on a piece of black paper, which renders the 

 particles easier to see. When torn up as finely as possible, a 

 cover-glass is placed on as before. The two rules to be borne 

 in mind in teasing are the following : 



1. Take a very small fragment to commence with ; hold it 

 with one needle, and tear it with the other. 



2. Tease it as finely as you can. Your object is to separate 

 the component parts from one another. 



C. Maceration. 



The process of teasing is in many cases facilitated by pre- 

 viously macerating the specimen, i.e., soaking it in some fluid, 

 which, while preserving the individual cells, tends to loosen 

 them from one another. The most important macerating fluids 

 are as follows : 



1. Ranvier's Alcohol ; a mixture of one part of strong spirit 

 with two parts of water. The specimen should be put fresh 

 into the mixture and allowed to remain twenty-four hours or 

 more. 



