THE BIOLOGICAL CHARACTERS OF BA- 

 CILLUS TYPHOSUS (EBERTH) AND BAC- 

 TERIUM COLI COMMUNE (ESCHERICH). 



BACTERIOLOGY offers so many problems for the 

 consideration of investigators in allied sciences that 

 the remarkable growth of a considerable literature in con- 

 nection with this subject is easily understood. Questions 

 which ten years ago were prominent, such as the mono- 

 morphic or pleomorphic characters of bacteria, have to-day 

 an interest which is secondary to their physiological and 

 pathological behaviour. The study of any single micro- 

 organism tends to confirm the belief in the flexibility of 

 form which many saprophytic and parasitic bacteria may 

 exhibit, and consequently investigations into the nature of 

 the exchanges of material exhibited by bacteria appears in 

 many cases to afford a safer guide for the determination of 

 definite specific characters than a too rigid adherence to 

 purely morphological features. Such considerations are 

 especially evident in connection with the marked variability 

 of such pathogenic forms as spirillum cholerse, bacillus ty- 

 phosus or bacterium coli commune. The bacilli of cholera, 

 according to the researches of D. D. Cunningham (i), show 

 no fewer than eight distinct species which differ in form and 

 cultural growth. Even if the contention that these species 

 simply represent nutritive modifications of a single definite 

 form (2) is sustained, it is abundantly clear that great 

 morphological variation may occur. Friedrich (3) has 

 undertaken a detailed study of cholera vibrios and has 

 arrived at the conclusion that the species described by 

 Cunningham are only multiple varieties of Koch's spirillum, 

 which undergoes alterations in form which it is impossible 

 to control ; the most abnormal comma-bacilli may at any 

 time take on the character which may be considered typical, 

 that is the form originally described by Koch. A second 

 distinct type of cholera vibrio exhibits longer and more 

 delicate filaments which are frequently twisted into a spiral. 



