564 PATHOGENIC MICROORGANISMS 



Trincas, and quoted from the First Volume of the Kolle and Wasser- 

 man Handbook. 



Toluidin blue 0.25 gram 



Alcohol 5 c.e. 



Two per cent acetic acid 100 c.c. 



Staining with this for one minute gives very much the same picture 

 as Loeffler's alkalin-methylene-blue, but rather a clearer contrast 

 between polar bodies and cytoplasm, and makes an eminently satis- 

 factory stain. 



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 8 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 ae'robe. Its preference for 

 oxygen is marked, but it will grow in anaerobic environment in the pres- 

 ence 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. Tem- 

 peratures 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 one minute. Low temperatures, and even freezing, are well 

 borne. Desiccation and exposure to light are not so fatal to this organ- 

 ism as to most of the other pathogenic bacteria. Sternberg 9 has found 

 it alive in dried bits of the pseudomembrane after fourteen weeks. It is 



8 Escherich, ' ' Aetologie, etc., d. Diphth., ' ' Wien, 1894. 

 Sternberg, " Manual Bac., p. 455- 



