70 PHARMACEUTICAL BACTERIOLOGY. 



II. Plate and Tube Cultures. (Lactose-litmus-agar.) 



1. Temperature diflEerential test. 



a. (20° C.) Colonies per c.c 



b. (38° C.) Colonies per c.c 



2. Color differential test. 



a. Pink and yellow colonies per c.c • ■ • 



c. Not pink or yellow colonies per c.c 



3. Colorless gelatin liquefying colonies per c.c. 



4. Neutral red reduction, + or — . 



5. Indol reaction, + or — . 



6. Gram stain behavior, + or — . 



7. Gas (hydrogen) formula. 



III. Agglutinating tests for Typhoid Germs. 



8. Staining Bacteria. 



Staining consists of the infiltration of the cell-substance with sdlutions of 

 various coloring materials obtained for the most part from the group of coal- 

 tar derivatives known as the aniline dyes. As is generally known, 'different 

 cells and different portions of one and the same cell react differently with 

 the various dyes used. This peculiar behavior brings out contrasts in 

 appearances which aid very materially in determining the morphological 

 characters. The prime object, therefore, in using stains is to aid in the study 

 of cell morphology. Different bacteria react differently with the several 

 stains used. Some species take certain stains very readily, while they are 

 quite indifferent to other stains. The vegetative cell stains much more 

 readily than do the spores. In fact, spores are stained with great difficulty; 

 however, after they are once thoroughly stained they hold the color 

 persistently. 



The dyes which may be used in bacteriologic work are of many kinds, 

 differing as to color and as to staining powers with different cells, cell-con- 

 tents, and cell-parts. They are usually classified as acid or basic. Eosin, 

 acid fuchsin, and picric acid are acid stains, and are said to be diffuse in 

 their effects, having no special af&nity for any special cell structure. Fuch- 

 sin, methylene blue, and gentian violet are basic, and appear to have special 

 attraction for bacteria and for plasmic and nuclear substances of cells gener- 

 ally, for which reasons they are most generally employed as bacterial stains. 

 Fuchsin is, in fact, about the only efiicient stain for endospores, while 

 gentian violet and methylene blue are excellent stains for the bacterial cell- 

 wall. 



It is known that certain substances possess the property of preparing the 

 bacterial cells in such a way as to induce them to take up the dye more 



