168 The Philippine Journal of Science im 



strains here used (G and H) ferment it. To these should be 

 added strain J, which was obtained after this phase of the work 

 was completed, but which shows acid production in other glycerin 

 media. The reaction with dextrin may be due to traces of 

 dextrose ; at any rate, being less than 0.5 per cent, it is so slight 

 as to seem negligible. 



With regard to the second group it is interesting to note that 

 in spite of the constantly negative results in the litmus media 

 with all of these but maltose, and the negative serum water and 

 irregular agar reactions even with this sugar, their bouillons 

 show a constant, regular acidification ranging from 0.6 to 1.9 

 per cent. 



While there is no distinction between American and Philippine 

 strains, there will be noted in the averages slight variations in 

 the total acid production by the different strains. Thus the old 

 New Orleans rat strain (A) and one of the Bureau of Science 

 strains (/) cause considerably higher acidification than the 

 others, while one of the Philippine strains in particular (strain 

 G) shows a constantly comparatively low acid tolerance. 



INFLUENCE OP SUGAR AND MEDIUM ON MORPHOLOGY 



The morphology of B. pestis has been so often and so exhaus- 

 tively described that but a few points in connection with the in- 

 fluence of the different sugars used merit brief notice. 



Three-day sugar-agar cultures. — All smears examined were 

 stained with Loeffler's blue. On dextrose, mannite, and levulose, 

 in which media fermentation begins promptly, smears uniformly 

 show much degeneration and involution. When acid production 

 appears late, the degeneration and involution occur to a less 

 degree. The cultures on sugars not acidified give well-stained 

 organisms, though variation in morphology in different instances 

 is marked. The same sugar, however, seems in the majority of 

 instances to produce somewhat similar effects in the different 

 strains. Salicin, for instance, usually produces long, often 

 thready and at times almost filamentous organisms (B. proteus 

 type) , not at all recognizable as B. pestis. Dextrin and arabinose 

 also show this tendency. On the other hand, glycerin induces 

 fairly constantly the formation of short, chunky, deeply staining 

 bacilli, often showing the typical bipolar appearance of B. pestis 

 in exudates. In a very few instances there were encountered 

 long pale organisms with deeply stained polar bodies, indistin- 

 guishable from B. diphtherise under the blue stain. 



Ten-day sugar-bouillon cultures. — The morphology in dextrose 

 and mannite bouillons differs as widely from that on the similar 



