408 



J. RUSSELL ESTY 



Vegetative cultures of Clostridium Welchii isolated from the 

 feces of man, cow and horse were more resistant than those 

 isolated from milk. In all cases, cultures from feces survived 

 59° for fifteen minutes while cultures from milk survived only 

 56°. Cultures from cow feces were the most resistant, 28 per 

 cent surviving 62°C. Pasteurization at 63°, however, killed all 

 the vegetative forms of Clostridium Welchii. 



TABLE 8 



Thermal death points. Table showing numbers of cultures from different sources 



surviving temperatures vs. 56° to 63°C; numbers surviving boiling in spore stage 



Milk. 



Human. 



Cow 



Horse , 



Combined. 



TIME SINCE ISOLATION 



4 months 

 3 months 

 1^ months 

 2 weeks 



2 weeks 

 Freshly isolated 



Freshly isolated 

 Freshly isolated 



TOTAL 

 NUM- 

 BER 

 CUL- 

 TURES 



20 



24 



6 



25 



19 

 36 



18 



18 



166 



TEMPERATURE °C. 



56 57 58 59 60 61 62 63 



Vegetative eight hours growth 



13 



16 



3 



10 





 



Conclusions. The thermal death point of vegetative forms of 

 Clostridium Welchii varies from 56° to 63° for fifteen minutes 

 and is not significant in the differentiation of the members of 

 the Clostridium Welchii group. 



The thermal death point of spores shows two distinct groups; 

 one whose thermal death point is 87° to 90°, and the other above 

 100°. Some strains from market milk survive 100° for thirty 

 and forty minutes, while spores from human feces do not survive 

 100° for fifteen minutes. 



There is no correlation between spores and vegetative forms 

 in corresponding cultures, nor is there any relationship between 

 the fermentative reactions and the thermal death points. 



