AEROBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 275 



the sporulating organisms by the use of carbohydrates. The 

 result of this work was not entirely satisfactory because of the 

 difficulty of estabUshing the fundamental species from which to 

 build up our system of classification. During the past few years, 

 however, a number of very valuable papers on spore-bearing 

 bacteria have appeared in the literature and have cleared up 

 some of the most difficult points. Of especial importance is the 

 work of Meyer (1903) and his collaborators, Gottheil (1901) 

 and Neide (1904) in Germany, and the work of Chester (1903) 

 in this country. As a result of the efforts of these authors we 

 now have accurate descriptions and definite means of identi- 

 fication of a small number of our most common spore-bearing 

 species. 



Some four years ago a large number of spore-bearing bacteria 

 was obtained from raw milk and from milk heated to various 

 temperatures from 60° to 100° and so much difficulty was en- 

 countered in their identification that it seemed as if the time was 

 ripe for a more extensive investigation of the subject, based 

 upon the work above referred to. The problem was first under- 

 taken by Mr. Lawrence and myself with the organisms from 

 milk. After a working basis had been obtained for the classi- 

 fication of these species a study of the spore-bearing bacteria of 

 water was undertaken by Dr. Laubach, and of the soil by Dr. 

 Laubach and Mr. Rice with the object of testing the classifi- 

 cation already adopted for milk bacteria and of adding to it such 

 species as had not previously been encountered in our work. 

 Finally stock cultures of well-known species were obtained from 

 the Krai collection in Vienna, the Winslow collection in the 

 American Museum in New York, from the laboratories of 

 hygiene of the University of Pennsylvania, and of the University 

 of Chicago, and the bacteriological laboratory of the Sheffield 

 Scientific School, and our cultures were compared with them. 

 From the start of the work however, our object has been to 

 establish clearly the different types of spore-bearing organisms 

 in our own laboratory and then to link these types up with types 

 already established by other observers. Altogether over 1700 

 cultures have been studied from various sources, milk, soil, dust, 



