BACTERIA 



however, it quickly dies. Does not resist drying or chemicals, 

 except carbolic acid, towards which it exhibits a tolerance. Sun- 

 light kills it in an hour. 



Habitat. It never exists in nature, except where water or soil 

 has been contaminated by feces or urine. It may multiply in po- 

 table waters, in milk, and the juices of oysters. 



Chemical Activities. Does not produce proteolytic enzymes; 

 forms H 2 S. but will not ferment the sugars with gas formation. 

 Does not yield indol or nitrites. Produces levorotatory lactic acid. 



FIG. 50. Seventy-two hour old culture of typhoid bacillus on gelatine. (Kolle 

 and Wassermann.) 



Its toxin is all contained within the bacterial cell (endo-toxins) 

 and is not water soluble. This toxin is manifested by injecting 

 washed and killed bacilli into animals, or by freezing the bacilli 

 with liquid air, and then crushing them. This injected into 

 guinea pigs causes diarrhoea, mydriasis and death. 



Oxygen Requirements. It is a facultative aerobe. 



Cultural Characteristics. It grows upon all media at the tem- 

 perature of the body, 37 C. and more slowly at 20 C. On gela- 

 tine plate it produces at first small colonies, yellowish and punctate, 

 which become whitish, delicately notched and ridged. (Fig. 50.) 



