LABORATORY AND GREENHOUSE STUDIES. 77 



ism. As much work has been done by various investigators toward 

 ascert^aining a ready means of identifying Bacillus coli, it has been 

 deemed advisable to consider these special means of identification 

 before taking up the many miscellaneous biological features com- 

 monly discussed in this sort of work. 



Special Test Reactions for the Identification of the Organism. 



Various bacteriologists, working in connection with public boards 

 of health or independently, have adopted routine methods for dcter- 

 minmg the presence of Bacillus coli in drinking water or elsewhere. 

 In some cases these methods are considered by their users as sufhcient 

 to ascertain definitely the presence or absence of this organism. In 

 other cases the probabilities are that the organism in question is 

 Bacillus coli or some closely allied form. The tests made consist of 

 only one or two or of several reactions. The adoption of the special 

 methods here will be of service, not only in characterizing the coconut 

 organism, but also in ascertaining any differences that there may be 

 between it and Bacillus coli. 



Of those reactions described in the following pages Dr. Theobald 

 Smith ^ claimed that the production of gas to the amount of 40 to 70 

 per cent in dextrose media demonstrated the presence of the colon 

 group of bacteria, the hog cholera group. Bacillus lactis aerogenes, and 

 Friedlander's bacillus. In order to determine from among these 

 various bacteria the ti'ue Bacillus coli, Dr. Smith suggested^ that the 

 following reactions were sufhcient: Growth on gelatin in the form of 

 delicate bluish or more opaque whitish expansions with irregular 

 margins; actively motile when examined in a hanging drop from 

 young surface colonies taken from the gelatin plates ; coagulation 

 of milk within a few days ; growth upon potato either a rich, pale 

 or brownish yellow deposit, or merely glistening, barely recognizable ; 

 also gives a distinct indol reaction. 



Behavior of the organism in the fermentation tube must conform 

 to the following scheme: 



Variety A: One per cent dextrose bouillon at 37° C. Total gas about one-half the 



volume of the closed arm. Proportion of hydrogen to carbon dioxide 



about 2:1. Reaction strongly acid. 

 One per cent lactose bouillon. As in dextrose bouillon with slight 



variations. 

 One per cent saccharose bouillon. Gas production slower than in the 



preceding. Total gas finally about two-thirds. Proportion of H to 



CO2 nearly 3 to 2. The final reaction in the bulb may be slightly acid 



or alkaline according to the rate of gas produced. 

 Variety B: The same as variety A, except that in saccharose bouillon neither gas 



nor acid is formed . 



1 Smith, Theobald. The Fermentation Tube. The Wilder Quarter-Century Book, 1S93, p. 229. 



2 Smith, Theobald. Notes on Bacillus Coli Communis and Related Form.s. American Journal of 

 Medical Science, vol. 110, 1895, pp. 283-302. 



228 



