AEROBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 277 



SPORE-BEARING BACTERIA IN MILK 

 BY J. S. LAWRENCE AND W. W. FORD 



It has been pointed out by a number of observers (Fliigge, 

 1904; Ford and Pry or, 1904) that milk heated to any tempera- 

 ture above 60°C, if kept in a warm place, shows an excessive 

 development of spore-bearing bacteria which are ordinarily 

 inhibited by the lactic acid bacteria universally present. Hueppe 

 (1884) was possibly the first to call attention to the presence of 

 aerobic spore-bearing forms in milk but it is impossible to say 

 now what his Bacillus butyricus (an aerobe) really was. Sub- 

 sequently Loeffler (1887) described an organism from boiled 

 milk which had been allowed to clot, under the name Bacillus 

 lactis albus, now known as Bacillus albolactus Migula. Con- 

 siderably later Flugge (1894) took up the question at some length 

 and described eleven different species found in boiled milk and 

 to them he ascribed an etiological role in the summer diarrhoea 

 of infants. Several of the organisms described by Flugge are 

 now considered identical with such common saprophytes as 

 Bacillus viigatus and Bacillus mesentericus while others can be 

 identified with diflSculty or not at all, as their originals have been 

 lost. During the past three years we have worked out the 

 morphological and cultural reactions of 250 spore-bearing 

 bacteria obtained from raw milk and from milk subjected to 

 various temperatures. The two most common species proved 

 to be Bacillus cereus of Frankland and Bacillus subtilis of Cohn. 

 In this differentiation we follow Chester who has given us a 

 definite and clear conception of Cohn's species and has taken up 

 at length the somewhat involved discussion concerning the two 

 organisms. As a result of his work Chester decided that the 

 real Bacillus subtilis of Cohn is one of the smallest of the spore- 

 bearing species, forms central or slightly excentric spores which 

 have a characteristic appearance and gives definite cultural 

 reactions. The reactions as outlined by Chester we are able to 

 confirm in the main but we disagree absolutely from him in his 

 contention that this species is identical with Bacillus vulgatus, 

 {B. mesentericus vulgatus) the old fashioned "potato bacillus." 



