1923] 



JENNISON— POTATO BLACKLEG 



33 



TABLE III— (Continued) 



MILK 





REACTION 20 





INCUBATED AT 28° C 







Plain milk 





Litmus milk 



Culture! 



Coagulation 

 begins 



Reaction 



Peptonization 

 begins 



Reduction 





6 days 



1 8 days 



of litmus t 





days 





days 



days 



160.1 



2 



+23 1 



+47 f 



3 



7-8 



170.3 



2 



+33 



+52 



3 1 



7-8 



180.2 



2 



+36 



+46 



3 



7-8 



183.2 



2 



+34 



+50 



3 



7-8 



187B . 1 



2 



+39 



+49 



3 



7-8 



191. 



None 



- 8 



+24 



None 



None 



194. 



2 







3 



1 7-8 



195. 



2 



+32 



+53 



3 



I 7-8 



196. 



2 



+34 



+52 



* 3 



| 7-8 



197. 



2 



+29 



+39 



3 



8-9 



198. 



2 



+10 



+35 



3 



12 



201. 



2 



+35 



+51 



3 1 



7-8 



* None of the strains changed the color of the medium. 



f Figures represent increase or loss in degrees on Fuller's scale over controls 



titrated on same day. 



X The indicator had very little, if any, effect on the growth. 



Cohn's solution. 



No growth. 



Indol production. — Negative. 



A survey of the published descriptions of the potato blackleg 



bacillus reveals the fact that half of the authors conclude that 



at an op- 

 were therefore taken by the 



this organism produces indol, while the others arrived 

 posite conclusion. Special pains 



of 



[•iter to determine th 

 Kligler ('14), Lewis 



and others have criticized th 



Salkowski-Kitasato method (cone. H 2 S0 4 and NaNO 



on 



f its unreliability. Kli 



(14) 



that this 



should be discarded, since a red coloration is frequently ob 



because the 



Ehrlich 



tained which is not due to indol; also 

 cultures which really produce indol is 

 method of testing for indol production was used by the writer 

 in his experiments. This test will detect indol in a dilution of 

 1:1,000,000. It has been shown that it is 10 times more delicate 

 than the older test mentioned above. In order to make his tests 

 even more searching, the writer employed both "Bacto" peptone 

 and Witte peptone in making the Dunham's solutions used as 



media 



f the blackleg bacillus 



fully tested, using controls inoculated with Bacillus 



blanks 



pink coloration did 



