124 



From an inspection of the foregoing table it is evident that, as a 

 rule, under the conditions named, Ps. hyacinthi reduced litmus only 

 ver}^ slowly. In litmus milk its first visible effect was a deeper bluing 

 of the milk, which persisted for some time; the casein was then thrown 

 down slowly, and a partial or complete reduction of the litmus usuallj^ 

 followed. Upon reoxidation, the litmus was again blue. Addition of 

 methyl alcohol led to no acid reaction. Addition of ethyl alcohol 

 caused the development of a slight quantity of acid, which inhibited 

 further growth, but did not immediateh^ destroy the organisms. This 

 acid is volatile and the boiling culture smells like acetic acid. Glycerin 

 retarded growth, no acid was formed, and the casein did not separate. 

 Addition of other substances to the litmus milk — e. g.,mannit, galac- 

 tose, cane sugar, grape sugar — led (during the first few weeks) either 

 to the formation of no acid or to the production of so slight a quantity 

 that it was easily obscured by the alkali. 



Ps. cmnpestris and Ps. 2>haseoli were also tested in litmus milk and 

 other litmus cultures. In general, their behavior was like that of Ps. 

 hyacint?ti. The milk first became deeper blue, the casein was then 

 thrown down slowl}'^, and the litmus was reduced. In some cases, at 

 least, the litmus was reduced more rapidly by these two organisms than 

 by Ps. liyacmtJii. On reoxidation the litmus was blue. 



The relative rapidity of the reduction of litmus is worth noting. 

 For instance, in some broths tinctured with this substance and inocu- 

 lated with Ps. hyacinthi^ all of the litmus color disappeared except in the 

 uppermost layers in contact with the air, but this reduction took place 

 slowly, requiring several weeks, where Bacillus cloacm consumed only 

 as many days. 



In a litmus cauliflower broth inoculated with Ps. hyacinthi reduc- 

 tion was first visible toward the end of the second week and was not 

 complete until after the third week. In the same broth inoculated 

 wHh Ps. phaseoli reduction began to appear at the end of the first 

 week and was complete at the end of the second week. In the same 

 broth inoculated with an undescribed organism belonging to the B. 

 cloacm group ^ there was partial reduction of the litmus in 20 hours 

 and complete reduction in 48 hours. 



Ps. stewarti cultivated in the same litmus milk behaved differentl}^ 

 It grew well, but the casein was not thrown down and a slight amount 

 of acid was formed. This is usually not observable the first week and 

 it is often obscured for a long time by the reducing action of the organ- 

 ism. The action of this germ on litmus milk is shown in the following 

 table: 



^ Isolated from rotting potato tubers received from Florida and designated in the 

 writer's notes as "The Florida gas-forming wet rot." 



