BACILLUS DIPHTHERIA 515 



The cover-slip preparation, after having been fixed, is stained with so- 

 lution No. 1 for one to three seconds. It is then washed in water and 

 immersed for from three to five seconds in solution No. 2. With this 

 stain the bodies of the bacilli appear brown, the polar granules blue. 



Another method which has been extensively used is that of Roux. 

 The solutions required for this are: 



1. Dahlia violet 1 gram. 



Alcohol, 90 per cent 10 c.c. 



Aq. dest ad 100 " 



2. Methyl green ' 1 gram. 



Alcohol, 90 per cent 10 c.c. 



Aq. dest ad 100 " 



The two solutions are mixed, one part of 1 being added to three parts 

 of 2. Preparations are stained in this mixture for two minutes. The 

 polar bodies appear a dark violet. Other methods for the staining of 

 polar bodies have been recommended. 



The significance of the polar bodies is not well understood. Their 

 discoverer, Ernst, regarded them as bodies analogous to the spores of 

 other organisms. The ease with which they are stained, however, and 

 the low temperatures to which the bacteria succumb make this appear 

 very unlikely. A more probable interpretation seems to be that of 

 Escherich * who regards them as chromatic granules. 



Stained by Gram's method, the diphtheria bacilli retain the gentian- 

 violet. 



In stained smears from the throat or from cultures a characteristic 

 grouping of the bacilli has been observed. They lie usually in small 

 clusters, four or five together, parallel to each other, or at sharp angles. 

 Two organisms may often be seen attached to each other by their cor- 

 responding ends while their bodies diverge to form a " V" or " Y" shape. 



Biological Characteristics. The diphtheria bacillus is a non-motile, 

 non-flagellated, non-spore-forming aerobe. Its preference for oxygen 

 is marked, but it will grow in anaerobic environment in the presence of 

 suitable carbohydrates. It does not liquefy gelatin. The bacillus grows 

 at temperatures varying between 19 C. and 42 C., the most favorable 

 temperature -for its development being 37.5 C. Temperatures above 

 37.5, while not entirely stopping its growth, impede the development 

 of its toxin. 



Resistance. The thermal death point of this organism is 58 C. for 

 ten minutes, according to Welch and Abbott. Boiling kills it in about 



1 Escherich, "Aetologie, etc., d. Diphth.," Wien, 1894. 



