266 STATE BOARD OF AGRICULTURE. 



free nitrogen from combined nitrogen, but that this liberation does not take 

 place through the agency of this germ very freely unless there is associated 

 with it another micro-organism which is known as the colon germ. 



These examples will be sufficient to meagerly illustrate the possibilities of 

 association in a world of micro-organisms. Farmers have doubtless recognized 

 that certain plants grow only in the presence of other plants, — again illustrating 

 in the higher world the effect of associative development. This may doubtless 

 be extended into the animal kingdom, and perhaps could be carried into regions 

 which we know nothing about at the present time. 



By the studies conducted in this laboratory, it has been possible to demon- 

 strate that when the lactic bacteria are associated with certain other, bacteria 

 the lactic germs are capable of producing a gi-eater amount of acid through this 

 association than when grown alone without the influence of any other germs; 

 that the milk in which the two germs are grown will lopper sometimes as 

 many as 72 hours earlier than the milk in which the lactic germs are grown 

 alone; that the number of lactic germs also increases much more rapidly when 

 under the influence of association than when alone. Allow A to stand for the 

 lactic bacteria, B to stand for the associated type, then the number of lactic 

 germs developing in single and combined culture may be represented as follows: 



A : A + B : : 27 : 1614 



It is also interesting to note that if we should allow the germs designated by 

 B to grow in milk for 48 hours, then kill them by sterilization, the milk in which 

 they have grown will give the same results as when the living germs B are grown 

 with the lactic germs. Products are formed by the growth of germs B in the 

 milk which do not yield to sterilization; in other words, they are stable. These 

 products have the same influence upon the lactic germs in influencing their 

 growth, in hastening the formation of acid, and in reducing the number of 

 hours necessary for the loppering of the milk as the living germs B. We may 

 conclude, therefore, that the products are probably the important influencing 

 agents. 



While it has been positively shown that certain micro-organisms may influence 

 the lactic bacteria in the souring of milk by hastening the process, and also that 

 these micro-organisms apparently exert their influence in the milk through the 

 formation of distinct products which in turn are capable of accomplishing in 

 the growth of lactic germs what the living germs have been demonstrated to 

 accomplish, there are also other factors entering into the study of this asso- 

 ciative action which must be carefully considered, otherwise erroneous conclu- 

 sions are likely to creep in. Among these factors the most important to the 

 mind of the writer is that of the possible variations in our cultures resulting 

 apparently from the differences existing in milks At first it was suspected that 

 by the use of dairy milks these differences in milks could be explained by the 

 formation of bacterial products through the rapid development of germs usually 

 pervading dairy milks. Studies conducted to determine whether this would lead 

 to the probable explanation resulted in finding some variation, for by taking 

 samples of milk from the dairy at different times it was discovered that when 

 tested the usual variation in acidity existed, but if subjected to heat the milk 

 did not always respond the same even when the acidities, measured by phenol- 

 phthalein, were identical. For instance, 20° sometimes loppered and sometimes 

 did not upon heating; 21° sometimes loppered and sometimes did not upon heat- 

 ing; 22° sometimes loppered and sometimes did not upon heating. If acidity 

 measures the time of loppering of milk, then we must conclude that the indi- 

 cator is not at all reliable; if the acidity is not the cause, we must seek another 

 explanation for the variation secured in this test. Going to the cows themselves 

 and securing milk that was perfectly fresh, it was found that the acidities, 

 measured by phenol-phthalein, were marked by great variations. To illustrate: 



Red Polled Pansy Belle gave 9° acidity. 



Grade 31 gave 18° acidity. 



Holstein College Houtje gave 5° acidity. 



Swiss College Becky gave 13° acidity. ^ ' 



Holstein College Belle gave 14° acidity. 



Grade 11 gave 17° acidity. 



Grade 17 gave 18° acidity. 



