EXPERIMENT STATION BULLETINS. 361 



ASSOCIATE MICRO-ORGANISMS AND " INFANT MILK." 



These studies have tliis significance in connection with furuisliing pure 

 food to infants: \Miile we have not demonstrated that the products mth 

 which we have been concerned in our associational studies are identical 

 with the products which are instrumental as the cause of gastro-intestinal 

 disturbances of infants, we have shown how rapidly these products are 

 formed in milk and thus far are only detectable by means of association; 

 for there may be no other apparent change in the milk and no alteration 

 whatever which can be determined b\' any method available at the present 

 time. 



There is required the micro-organisms capable of growing in milk and 

 coping with its associate micro-organisms in order to produce definite dis- 

 astrous results. Again, the very associations maj'' result in certain reactions 

 which give origin to the substances causing intestinal trouble. A^Hiatever 

 may be the interpretation, it is patent that associate micro-organishis exert 

 no salutary influence in "Infant Milk" unless it is by curtailing possible 

 danger by hastening the souring. 



STATEMENTS. 



1. The sample of milk, the temperature, the number of bacteiia present 

 and other factors may change the results of combination, but an average 

 result ma}'' be secured by holding to constant conditions throughout. This 

 work is based upon one set of conditions only. 



2. Because of the extensiveness of this work, it has been impossible to 

 follow intensively any of the many questions which have been suggested, 

 or which have pressed hard for recognition. 



3. Much greater satisfaction would be ours had it been possible to work 

 over each combination several times, and under somewhat different condi- 

 tions. After once establishing what was regarded as a fair test controlled 

 by checks, it became necessary to pass on. Throughout the investigations, 

 two series of flasks were always conducted, one series being emploj^ed to 

 check against the other. 



CONCLUSIONS. 



1. Bacteria, ordinarily found in milk, may or may not facilitate the growth 

 of lactic micro-organisms. 



2. About fifty-seven per cent of the associate micro-organisms when grown in 

 combination with the specific lactic micro-organisms accelerate their gro^-th 

 and action. 



3. The relative number of each micro-organism introduced into the com- 

 bination may or may not have a decided influence upon the acceleration 

 of the groAA*th of the lactic micro-organisms of lactic fermentation. 



4. Acceleration ma}' occur at the beginning of the fermentation, or at 

 the end, or at any stage between. 



5. The means b}' which this acceleration of lactic fermentation is ))r()- 

 duced is not the same in all cases. It appears to be due to products manu- 

 factured by the associate micro-organisms, sometimes stable to heat, some 

 times unstable; sometimes under alkaline conditions, sometimes under acid 

 conditions; sometimes with apjjarcnt digestion, sometimes with no appar- 

 ent digestion. 



6. It is veiy doubtful Avbether these products combine with the inorganic 



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