108 STUDY AND IDENTIFICATION OF BACTERIA 



growth and the development of phenol and various putrefactive sub- 

 stances. The probable importance of the colon bacillus in protecting 

 the organism is shown by the fact that where numerous colonies of patho- 

 genic organisms may be cultivated from fseces we may find a diminu- 

 tion in number or absence of the colon bacillus. This condition may be- 

 observed in infections with the organisms of dysentery, cholera, typhoid, 

 and paratyphoid. While its normal function is probably protective, 

 yet the B. coli is an important pathogenic agent, it being frequently the 

 organism isolated from purulent conditions within the abdominal cav- 

 ity, especially in appendicitis and lesions about the bile ducts. It is 

 particularly prone to cause lesions of the bladder and pelvis of the kid- 

 ney. In the treatment of colon cystitis by vaccines of dead colon 

 bacilli, the most brilliant results in opsonic therapy have been obtained. 



Sir A. Wright thinks that certain cases of mucous colitis may be due 

 to colon infection and that vaccination may cure them. The colon 

 bacillus is fully considered under the bacteriology of water. 



B. CLOACA was isolated first from sewage by Jordan. It is, as a rule, 

 a rapid liquefier of gelatin, and in its reactions with sugars and litmus 

 milk resembles the colon bacillus. 



Where the gelatin liquefaction is slow or slight it may be distinguished 

 from B. coli by its gas formula which is about three times as much CO 2 

 as H, just the reverse of that of the colon bacillus. B. lactis aerogenes 

 is often found in sewage. It is one of the causes of the souring of milk. 



B. ACIDOPHILUS, B. BlFIDUS, B. BULGARICUS. 



These are often termed the long rod group of lactic acid bacteria 

 in contradistinction to certain other Gram positive bacilli which 

 are short and oval and which are confused with the so-called milk 

 streptococci. 



The long rod group often forms chains and often shows metachromatic granules 

 which stain with Neisser's method. They are'readily distinguished from Gram nega- 

 tive lactic acid producers, of which the type is B. lactis aerogenes, by their Gram 

 positive staining. B. acidophilus often give the impression of a diphtheroid in a 

 Gram stained faeces smear. It is nonmotile and often shows polar granules. Grows 

 only at temperatures above 22 C., op. 37 C. It grows better anaerobically than 

 aerobically and then shows the clubbed involution characteristics of B. bifidus; 

 so that some consider these organisms the same, the morphology of B. bifidus being 

 the result of anaerobiosis. Original cultures are best made in i% glucose and i% 

 acetic acid bouillon. Some authorities consider B. bifidus the most important 



