78 PATHOGENIC BACTERIA 



in the flame. After inoculation the culture tube is incubated 

 at 37 C, having been first capped to prevent any drying of the 

 medium. Incubation of the tube is essential, and without an in- 

 cubator the further investigation is preferably handed over to an 

 expert or to one of the Associations or Institutes where such 

 work is carried out. 



Culture tubes and swabs may be obtained, moreover, from 

 many such sources. After twenty-four hours' incubation the 

 growth of the diphtheria bacillus appears as small hemispherical, 

 greyish, shining colonies; where such have arisen so closely as to 

 coalesce the circular outline is wanting. As a rule, colonies of 

 other bacteria develop concurrently, such, e. g., as staphylococcns 

 pyogenes aureus, staphylococcus pyogenes albus, streptococcus 

 pyogenes, sarcina lutea, or forms of yeasts. The colonies of the 

 diphtheria bacillus cannot be distinguished with any certainty 

 by their macroscopic characters, though yellow colonies may be 

 ignored. If no suspicious colonies appear for individual exam- 

 ination, the 6se is swept over the culture and the material trans- 

 ferred to cover-glasses, on each of which a drop of distilled water 

 has been previously placed, the examination being made in the 

 dried state, by the technique fully described in Part I. 



Labor may be saved by using a single, long cover-glass on 

 which a series of such preparations may be made and stained, in 

 place of separate circles or squares. 



The films having been allowed to dry, they may be stained 

 with carbol fuchsine or by Gram's method, but as satisfactorily 

 and simply with Loffler's methylene blue as with any other 

 dye: 



Concentrated Alcoholic solution I Solution of Potash (1-10,000) 



of Methylene Blue 30 parts | 100 parts 



The stain is allowed to act for five minutes and washed off 



