330 THE AMERICAN MONTHLY TNov 



moved at pleasure. Every pains must in any case be 

 taken to exclude insects. 



For simple microscopic examination it will be found 

 convenient to first wet the material with alcohol on the 

 slide, then with a weak solution of potassic hydrate, to 

 cause the spores and other structures to assume proper 

 plumpness. A little glycerine may be added or run un- 

 der the cover if it is desired to preserve the material for 

 further or prolonged study. For permanent mounting 

 nothing in most cases is better than glycerine jelly. As 

 a preparation, the material should lie for some time in 

 Hantsch's fluid, opportunity being given for evaporation 

 of the alcohol and water. When the material shows the 

 proper clearness and fullness, it may be mounted in jelly 

 in the usual way. Kaiser's formula gives beautiful re- 

 sults. After mounting, the preparation should be sealed 

 with some good cement, as Hollis's glue. 



Preparation of Certain Special Media. 



V. A. MOORE. 



In studying the properties of bacteria it is desirable 

 to cultivate them on a number of different media. Bouil- 

 lon, agar, and gelatin are most commonly used, but others 

 are necessary in determining the cultural peculiarities 

 and important biochemic properties of the organism in 

 question. The cultivation of bacteria upon these media 

 may be regarded somewhat as a test, to determine the 

 presence or absence of certain properties. Thus, for ex- 

 ample, will the species in hand coagulate the casein in 

 milk, produce gas in media containing saccharose, grow 

 on potato, etc.? The number of these tests which have 

 been used and called important is large. A few species 

 of bacteria require a particular kind or kinds of media 

 for their diagnostic or most differential growth. Among 

 these are those of glanders, diphtheria and tuberculosis. 



