242 PUBLIC HEALTH BACTERIOLOGY 



capsulatus ; bacillus of rhinoscleroma. Both these 

 bacilli differ only in not fermenting dextrose. 



B, Lactis Aerogenes Is a widely distributed organism, 

 and was isolated by Escherich in 1885 from the faeces of 

 infants. It is almost constantly present in milk, faeces, 

 sewage, and water. It differs from B. coli, which is found 

 in like circumstances, in being non-motile and non- 

 flagellar, in possessing a capsule in milk cultures, in 

 fermenting saccharose and starch but not dulcite ; and 

 in not forming indol. 



Cultures. It grows readily on all media. 



In broth, it forms a pellicle, and causes general clouding. 



On agar and gelatin, it forms a heavy white growth. 



In gelatin stab, it gives a nail-head growth. 



On potato, it grows well and forms gas from the starch. 



In Milk, acid formation and coagulation are rapid. The 

 clot is not digested by the bacillus, and in ordinary souring 

 of milk the germs present which produce proteolytic 

 ferments have their growth restrained by the large amount 

 of lactic acid formed by the more rapid action of B. 

 lactis aerogenes. It is scarcely pathogenic, though 

 flatulence in infants has been attributed to its action, 

 and a cystitis in which gas was formed in the bladder, 

 associated with an acid urine. For animals, its patho- 

 genicity is not properly established, the reports being 

 contradictory. It is an aerobe, but a facultative anaerobe. 

 Optimum temperature, 25 to 30 C. B. lactis aerogenes 

 is distinguished from Friedlaender's bacillus by its invari- 

 able and rapid curdling of milk; but some authorities 

 consider it to be identical with that organism. 



BACILLUS ACIDI LACTICI (HUEPPE), 



This bacillus is present in milk, which it curdles and 

 acidifies. It does not ferment saccharose or dulcite. 



B. acidi lactici (Leichmann) is believed to be really a 

 streptococcus, the Streptococcus lacticus (Kruse), which 

 Heinemann states is a variety of the Streptococcus pyo- 

 genes. It is present on the cow's hide, in cow dung, and 

 in milk from the first stage of milking. 



