to modify greatly the acid producing characteristics of the diphtheria 

 group of organisms. 



The present paper is a report of the results of an investigation upon 

 the variation and carbohydrate metabolism of the bacilli of the P r o t e u s 

 group. In view of the fact that this group of organisms is found widely 

 distributed under varied conditions in nature, it offers a promising field 

 for investigation. 



Historical. 



The members of this group of micro-organisms were first isolated 

 by Hauser (9) who regarded them as the chief bacteria concerned in 

 the process of putrefaction. He isolated three forms which he originally 

 regarded as distinct species, but his later observations led him to believe 

 that all three forms are but varieties of the same species. Since then, 

 they have been isolated many times from sewage by many different in- 

 vestigators. Schnitzer (10) isolated a nember of the Proteus group 

 from a case of cystitis. Flexner (11) found it in a case of peritonitis, 

 and Reed (12) found aProteus organism associated with the P n e u m o - 

 coccus in a case of croupous pneumonia. Levy (13) isolated aProteus 

 form from a sample of beer yeast. Wyss (14) obtained B. vulgaris 

 from dead fish. Silberschmidt (15), Gluckman (16), and others 

 have isolated members of the group from infected meat. 



Ward (18) studied a number of organisms of this group which he 

 isolated from the Thames and came to the conclusion that Hauser's 

 three species of Proteus, together with several others isolated by 

 himself, are merely variations of one species. He considers them similar 

 in size and form, mode of growth, formation of zooglea, etc., but as 

 varying in detail as to rapidity of growth and liquefaction, and consequent 

 differences in the extent and appearance of the colony, and as to the 

 intensity of pigmentation. Fuller and Johnson (19) regard all non- 

 fluorescent, non-chromogenic gelatin liquefying bacteria forming proteus- 

 like colonies on gelatin, as belonging to the Proteus group. Ford 

 (20) includes under the Proteus group all organisms which liquefy 

 blood serum, casein, and gelatin, produce cloudiness in broth but no 

 scum, render milk acid, then alkaline, and which ferment dextrose with 

 gas formation. J o r d a n (21) includes under the P r o t e u s group, organisms 

 which ferment sucrose and dextrose, rarely lactose, which are for the 

 most part vigorously proteolytic, rapidly liquefying gelatin and blood 

 serum and precipitating and then dissolving casein. 



All of the above authors seem to lay special stress on the proteolytic 

 and fermentative properties of this group. It becomes essential, therefore, 

 to endeavour to establish the factors which may influence either one of 

 these characteristics. 



Source of cultures. 



The organisms used in this investigation were obtained from the 

 laboratories of the University of Michigan, University of Pennsylvania, 

 University of Illinois, University of Chicago, the laboratory of the Public 

 Health and Marine Hospital Service, Washington and from Krai's 

 laboratory. 



All cultures were rejuvenated according to the method of Fuller 

 and Johnson. Transfers were made from the gelatin plates to slant 

 agar. These were incubated for 24 hours and used to inoculate all the 



