236 



STATE BOARD OF AGRICULTURE. 



cent aqueous methylene blue solution, destained to a light blue color in 

 alcohol and dried. Duplicate smears were always made for each sample. 

 The counting was done under a compound microscope in the same manner 

 as in the Breed method. In this work an E. Leitz 1-12 oil immersion ob- 

 jective was used with a No. 1 ocular and the draw tube adjusted to 152 mm. 

 There was also used a special ocular micrometer marked into quadrants 

 with cross-hairs and a circle 8 mm. in diameter. This combination gives 

 a factor of 650,000 for every bacterium seen in one field. From 10 to 40 

 fields were counted and averaged per sample. The following results were 

 secured (see table) : 



"In every case when the cream was first pasteurized the results by 

 the microscopic group count were higher than by the plating method, 

 which is not surprising since the dead cells would stain as well as the 

 living ones. But where raw cream was used the results by the plating 

 method are higher than the microscopic group count. This is opposed to 

 all experience with the microscopic technique when applied to milk, 

 where one usually gets results from 2 to 5 times as large with the mi- 

 croscope as with the petri plate. The reason for this is not' clear though 

 our experience with sample No. 10 suggests a partial explanation. Repre- 

 sentative colonies on the plates were fished, grown in milk, and stained. 

 It was found that the bacteria took the stain very poorly. Various stains 

 were tried but with little better success except with Giemsa's stain which 

 differentiated the bacteria and the casein of the milk very well, when 

 the culture was grown in milk. But when this stain was applied to the 

 butter smears it did not stain the bacteria more successfully than other 

 stains. Another possible cause for overlooking bacteria in counting the 

 smears is the small size of the usual flora of butter, which consists prin- 

 cipally of Bacterium lactis acidi. Neither of these suggestions seems to fully 

 explain the discrepant results and further search is being made for the 

 reason. In two of the experiments the non-aqueous portion was examined 

 for bacteria but none were found. It is realized that the foregoing dis- 

 cussion is based on very few data. The main reason for presenting it at 

 the present time is in the hope that some suggestion may be received that 

 will help to solve the difficulties encountered." 



Miss Northrup reports on her Adams project in the following words: 

 "Succeeding the entrance of 1st Lieut. J. F. Morgan into the Medical 

 department of the army, I was placed in charge of the soil work in- 

 cluding experiments already started. After a year's work, I am able to 

 give the following report of progress. 



