194 TECHNOLOGY OF BACTERIA. 



hours : distilled water 100 c. c., saturated alcoholic 

 solution of methyl blue 20 ID. c., formic acid 10 

 minims. 



According to Koch the bacillus of leprosy has 

 the same color reaction as the tubercle-bacillus, 

 while all other bacteria known to him differ from 

 these in that the color imparted by one of the 

 aniline dyes is discharged by visuvin and by nitric 

 acid, used as above directed. 



The tubercle-bacilli stained by any of the meth- 

 ods given are likely to fade after a time, especially 

 when mounted in fluid, e. g., glycerine or water. 



4. PHOTOGRAPHING BACTERIA. Bacteria are 

 prepared for photography as above directed ; that 

 is, a thin film of the material containing them is 

 attached to a cover-glass by drying, stained, and 

 mounted over a shallow cell containing fluid, or in 

 balsam. For the larger forms methyl-violet is a 

 suitable stain for this purpose; but a color less 

 transparent for the actinic rays, such as aniline- 

 brown or visuvin, will be required for the smaller 

 species. 



The writer has given an account of the technique 

 of photo-micrography in another work, to which 

 the reader desiring fuller information is referred. 1 



It is but fair to say that satisfactory results can 

 only be obtained by the expenditure of a consid- 

 erable amount of time and money, as the work 



1 Photo-Micrographs and How to make them. James R. Osgood & 

 Co., Boston, 1883. 



