EXPERIMENT STATION REPORTS. 145 



SAMPLE III. 



hrs 221,000 17° 



7 hrs 1,780,000 19° 



23 hrs 3,800,000 19° 



32 hrs 204,000,000 19° 



47 hrs 1,633,000,000 43° 



53 hrs 1,936,000,000 63 



71 hrs 853,000,000 72° 



SAMPLE IV. 



o 



hrs 22,000 15° 



81/2 hrs 58,000 15° 



24 hrs 988,000 15° 



32 hrs 2,090,000 15° 



48 hrs 24,000,000 14° 



56 hrs 478,000,000 16° 



72 hrs 789,000,000 20° 



80 hrs 914,000,000 34° 



96 hrs : 960,000,000 63° 



104 hrs 2,000,000,000 77 



o 



I submit the above tables to illustrate the fact that the number of 

 micro-orgauisms at the end of 24 hours is not necessarily a guide to 

 the number on the start or that, if the established time for counting 

 were at the end of twenty-four hours, would the results of the count 

 by determination of species be a necessarily true index of the germ 

 content. 



Still again, another point that was very forcibly illustrated in con- 

 nection with these studies, was the difficulty in securing satisfactory 

 and logical counts of some species of micro-organisms. Making every 

 effort to have these counts result in logical sequence from their re- 

 spective dilutions, it was found that it was practically impossible to 

 succeed. This, of course, was found only with certain micro-organisms; 

 other micro-organisms seemed to lend themselves freely to dilution with 

 excellent results. 



We attributed these experiments to one of these causes: 



1. Tenacious grouping of micro-organisms in which the adhesive walls 

 barred detachment of single cells. 



2. Overcrowded plates manifest associative influences which may be 

 antagonistic or favorable. 



In this connection I wish to speak of still another interesting matter 

 connected with our "Associative Studies" which at the time the work 

 was conducted appeared very significant, but the conclusion was re- 

 versed in the butter studies a little later. We found that whey agar 

 gave better conditions for growth of lactic acid bacteria than an ordin- 

 ary agar. Although it was not universally true so noticeable was it 

 at times, that development of lactic acid types seemed to depend entirely 

 upon the nutrient conditions furnished by the whey agar. 



In the butter studies as conducted by Mr. Sayer, Mr. Rahn, and Miss 

 Farrand, it was found that the lactic acid micro-organisms grow well 

 19 



