PREPARING AND MOUNTING BACTERIA. 199 
some decided colour select that which seems to show it best. It 
may be a fancy, but I think any one who will take the trouble to 
experiment a little in this matter, will feel repaid by the improved 
appearance of the objects and the greater comfort in studying them. 
—American Society of Microscopists. 
PREPARING AND MOUNTING BACTERIA. 
By Prof. f. J.) BURRILL,» Phe Di) ERE: 
N my work I have not attempted to compare the results of the 
J. various new staining materials, many of which I have not seen, 
but what follows is some account of ordinary laboratory manipula- 
tion with common analine colours, such as can be obtained at any 
drug store for the colouring agents. Want of sufficient chemical 
knowledge has made it impossible for me to prosecute any syste- 
matic experimentation for the accomplishment of new results, and 
the pressure of other duties has been too great for the record of 
such achievements as should be presented in a paper of this kind. 
I can, therefore, only beg the indulgence of my fellow-workers 
whose practice has been more considerable and whose attainments 
are much more commanding than my own. A full account of my 
attempts to properly stain bacteria would be the record of more 
failures than successes, judged from my own estimate of what the 
latter should be, and this, not only at the outset of experimentation 
on several species, but more or less throughout the work. It is 
true there are species that may be very readily stained with scarcely 
a failure, by the use of common aniline, violet ink and other dyes, 
and this, too, without after-washing, leaving the material in which 
the organisms are imbedded too deeply coloured ; but what seems 
altogether satisfactory for temporary examination in these cases 
does by no means answer for all purposes nor with all organisms. 
The stain is not effective, or not suitable, or not permanent, or 
defective in one or more of several other particulars. 
I enumerate some elements of successful staining, as follows : 
1. The organisms should be decidedly and conspicuously 
coloured. 2. The general mass of imbedding material should be 
left unstained, or so different in colour that the organisms can be 
distinctly seen. 3. There should be no granular or other precipi- 
tations from the staining material, nor should any portion of the 
latter remain as a coating on the glass. 4. The colour should be 
suitable for the purposes required, and permanent, if the object is 
to be mounted for the cabinet. 5. The process should be as simple 
as possible and free from manipulative difficulties. 
