42 Comparative Studies 



The colonies on agar plates of cultures 13, 20, 26, 27 

 and 29 were somewhat more dense than those of the Loffler 

 bacillus, and they were also slightly yellowish in color ; 

 otherwise they resembled those of the Loffler bacillus. 

 The colonies of the other cultures resembled those of the 

 L6ffler bacillus quite closely. 



The cultures were studied for some time with regard to 

 the effect of Neisser's differential stain. They were grown 

 on Loffler's blood serum at a temperature of 34 C. for from 

 ten to twenty hours, and were then examined. Cultures 

 5, 1 8, 20, 21, 23, 26 and 29 showed more than the usual 

 number of bacilli with deeply-stained polar granules ; all 

 the other cultures, except 13, showed only an occasional 

 bacillus with the polar granules stained. Culture 13 

 seemed to show the granules stained as uniformly as the 

 cultures of the Loffler bacillus, though the morphological 

 characters of this bacillus are different from those of the 

 Loffler bacillus. These results coincide with the state- 

 ments of Neisser that the cultures of the pseudo-diphtheria 

 bacillus show only an occasional bacillus with the polar 

 granules stained. Control cultures of the Loffler bacillus 

 grown under the same conditions always showed most of 

 the bacilli with the polar granules stained, or even with 

 three, four or more granules in each bacillus. 



Experiments were made with a large number of different 

 aniline stains, in watery solutions, with and without de- 

 colorizing agents, with the hope of discovering additional 

 methods of differentiation between these groups of organ- 

 isms. No very satisfactory results were obtained, though 

 the following stains served to differentiate between the 

 pseudo-diphtheria bacilli and the Loffler bacilli ; but the 

 differentiation was in no case more definite than by Neis- 

 ser's method : 



i. Loffler's alkaline methylene blue, one minute, wash 



in water. 

 Lugol's solution, one minute, wash in water. 



