PREPARING AND MOUNTING BACTERIA, 201 
zole, or oil of cloves, into balsam ; but in the case of bacteria dried 
on the cover-glass these preliminary immersions are unnecessary. 
The mounting is direct in pure balsam, care being taken that the 
prepared material is thoroughly dry. The colour stands under sub- 
jection to the heat necessary for hardening the balsam. In the case 
of sections containing organisms, clearing agents are required, and 
may be freely used with at least certain species of bacterla—e.g., 
those commonly found on the mucous surfaces of the human body. 
I have not noticed this difference in permanence of colour in the 
case of other anilines in glycerine ; neither do I esteem the solu- 
tions in the latter always better than those in water or in alcohol, 
but in all cases in which the glycerine solutions are as effective they 
are to be preferred to others on account of the ease of handling. 
The alcoholic dyes are much inclined to creep or run over or up 
the surfaces of the containing dishes, and he is an expert workman 
who can leave his practice with clean fingers, to say nothing of for- 
ceps, needles, and perhaps of the work-table. Besides this, the 
alcohol on exposure rapidly evaporates, and often precipitations 
and sedimentary deposits mark the results. I do not know how 
others avoid this escape of alcohol when either on account of the 
necessities of the stain or of other business it must be left many 
hours. I have nothing better than a nest of ordinary porcelain 
dishes, the edges of which when necessary are smeared with 
glycerine. Stoppered bottles are not convenient. For the aqueous 
solutions these dishes are all that can be desired, unless intense 
heat is to be applied, when watch glasses take their place ; but with 
the watery colours and much more so with the glycerine solu- 
tions, nothing is needed for a staining vessel. The dye is simply 
placed in a little pool on the prepared cover-glass, and the latter is 
held in pliers, or placed on a level surface, where, in the case of 
the glycerine, it may be left any Jength of time if protected from 
the dust. When ready it may be taken again in the pliers, washed 
by a stream from a wash-bottle with either water or alcohol, or both, 
without during the process losing account of the surface of the 
glass on which the material exists. Ifa second glycerine colour is 
to be applied, this can be done at once in the same way without 
stopping for drying or for other preliminaries. 
Suppose one wants to examine the organisms in his own or any 
other person’s mouth. He may proceed as follows: Secure a little 
mucus from the tongue or teeth, taking care to avoid the remnants 
of the last bread and butter enjoyed. Place the substance ona 
clean glass slip, and if necessary mix by stirring. Make a little 
spatula of wood a quarter of an inch wide and cut square at the 
end, with which smear a well-cleaned cover glass, after the manner 
of spreading blood by drawing the spatula with the material once 
or twice, side by side, over the desired surface, holding the instru- 
