MICROANALYTICAL AND BACTERIOLOGICAL LABORATORY 427 



Wrigth's and Giemsa's. (Consult some modern work on Bacteriology or 

 Parasitology as to the methods for preparing any of the desired«stains). 



2. Balsam Momits. — Canada balsam, suitably diltued with xylol, 

 benzol, oil of cloves, ether, etc., is used for making permanent mounts. 

 The balsam should be diluted to the consistence of thin syrup, or rather 

 thin oil. In fact it should be thin enough so that when a droplet is placed 

 near the edge of a cover glass upon a slide, capillarity should draw it under 

 and spread it evenly. Xylol is one of the best diluents for Canada 

 balsam. Oil of cloves is objectionable because it destroys more or less 

 of the color of the stained mounts. Otherwise it is excellent. 



The thing of special importance is to remember that all substances 

 which are to be mounted in Canada balsam must be entirely free from 

 moisture: if any considerable moisture is present the mounts become 

 worthless, because the water will not mix with the balsam, forming opaque 

 emulsions. All substances which contain moisture may be dehydrated 

 by placing them in alcohol for a short time, untU the water has become 

 diffused into the alcohol and evaporated. After dehydrating, the material 

 should be placed into xylol (or the same substance in which the balsam is 

 dissolved) for a few seconds and then mounted in the balsam. Balsam 

 mounts are of course permanent. 



3. Glycerine Mounts. — Glycerine, or equal parts of glycerine and 

 water, makes an excellent mounting medium and has the advantage over 

 balsam in that moisture and water does not interfere with its use. Such 

 mounts will keep for months and even for longer periods of time, but 

 require careful handling, as they are easily removed from the slides. If 

 care is observed in mounting (using just enough of the mounting medium) 

 and placing the cover glass carefully) and the mounts are placed m suit- 

 able slide boxes, they may be kept indefinitely. The glycerine does not 

 evaporate, or if it does vanish partially with time, more may readily 



be added. 



Balsam mounts as well as glycerine mounts require the use of cover 

 glasses. The operator should bear in mind the effects produced by the 

 mounting processes. Heating and dehydrating causes a reduction m 

 size and some slight distortion in form. The reduction in size may be 

 considerable, a fact which must be kept in mind when comparing one and 

 the same organic substance examined in the fresh state and m the per- 

 manent mpunts. . , i„<.„i„ 



A cabinet may be perfect in arrangement and it may be completely 

 stocked and each and every article contained therein may be fuUy^and 

 fccuratelv labeled, and yet such a cabinet would be oHittle Pr-tif ^^^^^^ 

 is there is no way of locating the articles therem contamed Just as it 

 sLuld be made a criminal offence to write a book (especially a book of 



