284 L. D. BUSHNELL 



canned foods. He states that in commercial canned foods gi%ang 

 no evidence of spoilage, microorganisms were found in 179 out of 

 a total of 782 cans, or in 23 per cent of the cans. The spore- 

 bearers were practically the only organisms present, due to their 

 superior resistance to the sterihzing process. Viable spores were 

 found in 19.2 per cent of the non-leaking cans. Of the types of 

 bacteria isolated, B. mesentericus predominated, with B. subtilis 

 next. This author concludes that the living spores in commercial 

 canned foods are unable to grow, due to the absence of oxygen, 

 and that the vacuum is essential to the preservation of canned 

 foods under the present method of processing. 



Chejmey, in 1919, reported B. mesentericus in apparently 

 perfect cans, which were given a standard processing. 



Hunter and Thom, in 1919, made an examination of 530 cans 

 of canned salmon and found 237 unsterilized. 234 of these cans 

 contained the same organism of the B. mesentericus group, either 

 in pure culture or in connection with other species. Only 13 

 showed active spoilage. 



From the above it is evident that the aerobic spore-bearing 

 types predominating in unspoiled canned foods belong to the 

 B. mesentericus and B. subtilis groups of bacteria. 



We may consider three reasons why these organisms predomi- 

 nate in foods under such conditions : 



1. Spores of certain types predominate on the product as it 

 goes into the container. 



2. Spores of certain types are more resistant to heat than 

 spores of other types. 



3. The spores of certain types are not all destroyed during the 

 processing period and those remaining are able to grow under 

 conditions as they exist in the container. 



From the results obtained in this laboratory, it is evident that 

 B. mesentericus predominates, with B. subtilis second in number 

 among the aerobic spore-bearing types. We have no idea of 

 the number of each type upon the raw product as it went into 

 the jars, so that it is not possible to consider this point except 

 in so far as we may apply the work of Bruett (1919) upon the 

 death of bacteria. She concluded that the death rate followed 



