1 86 Journal of Agricultural Research voi. xxn. no. 4 



absent in old meal or meal made from old and thoroughly dried corn. 

 Micrococci are constantly encountered in culture but have not been 

 typed. Aerobic spore formers of the mesentericus group are always 

 present, and in spore form they constitute the larger part of the living 

 bacteria in some meals after long storage. 



This was clearly demonstrated by a series of experiments upon the 

 possibility of producing a sterile meal with steam, dry heat, or both 

 (unpublished cultural results of Ruth B. Edmondson). The spores of 

 this group survived more heating than could be applied under practical 

 working conditions to the product. Aside, however, from meal so wet 

 as to be unmarketable, these experiments show no evidence of bacterial 

 activity. One sample of apparently sound yellow meal showed the 

 presence of Bacillus niger Migula in such extensive numbers that masses 

 of meal placed upon culture media were promptly overgrown and with 

 the agar turned bluish black with this species. The meal was contributed 

 by Dr. S. S. Adams, of Washington, D. C, who reported the feces of a 

 child apparently well to have been blue when fed this meal. 



When, however, com or meal is bottled and incubated at laboratory 

 temperature (20° to 30° C), those species capable of developing under 

 the conditions presented show active growth. In the authors' series 

 such growth was not detected by physical appearance in products carry- 

 ing less than 13 per cent of moisture. Certain stone-ground samples of 

 Winton's series (8) showed some evidence of mold activity below that 

 figure. Measurable changes in quality certainly occur in such meals 

 during storage. Some experimental results have suggested the possibility 

 that these changes in such meal are due to the distribution of infected 

 material throughout the mass by the grinding of infected corn. This 

 conflicts with the current trade belief that the natural enzyms of the 

 germinal area are the chief causes of such deterioration, but reflects the 

 findings of HofTer (5) and his coworkers that even selected seed com 

 may be extensively infected. Examinations of commercial samples in 

 the Microbiological Laboratory have shown extensive development of 

 molds within the grain itself in com of other than the higher grades. 



In samples carrying 14 to 15 per cent of water the formation of balls 

 and concretions in the meal begins to be evident. The principal agent 

 in their formation appears to be Aspergillus repens, although many diffi- 

 culties are encountered in fixing a minimum moisture percentage for 

 the activity of this species. Changes involving the development of 

 mold mycelium in the meal begin within the limit of 13 to 15 per cent 

 of moisture. Incubation at 20° to 30° C. merely accelerates changes 

 which would progress more slowly in colder places. Moist chamber 

 experiments with meal inside this range of water content show the 

 presence of active mycelia of more than a single species, but principally 

 Aspergillus repens. When the percentage of moisture reaches 16, sev- 

 eral species are clearly able to grow. Special studies with Aspergillus 



