lactici. 



GuELPH Methods. 

 The Guelph Methods. One-half or one gram of cheese was taken and 

 pulverized in a sterile mortar, with ten grams ot powdered glas. thorough y 

 t ilized; and 50 cc. o^f sterilized warm water (37 degrees C.) was gra^^^^^^^^^ 

 added with constant stirring, to make a fine emulsion. And ye think that by 

 taking cheese in considerable quantity from different parts of the interior of 

 the plug and pulverizing the samples with sterilized powdered glass, using ten 

 <xrams of powdered glass for each gram of cheese, more accurate results were 

 obtained than could be secured by the methods followed in former investiga- 

 tions. When these larger amounts of cheese were used, the quantity of the 

 diluting fluid had to be considerably increased, and the labor of preparing the 

 samples was much greater; but undoubtedly the results obtained were more 

 accurate and gave a more reliable estimate of the bacterial content of the cheese 

 For the larger number of the Guelph analyses, one gram of cheese was used. 

 In a few insta,nces five grams were used. 



From the first dilution, one or two cc. were transferred to a measured 

 amount of sterile water in a sterilized flask. After thorough shaking, a meas- 

 ured quantity was again transferred to a measured amount of sterile water m 

 another sterilized flask; and, after further shaking, various quantities of this 

 third dilution were added to the culture media. For transferring portions of 

 the mixture from one dilution to another, straight-.sided (Mohr) pipettes were 

 used, and great care was taken to keep the liquid in the pipette in motion; for 

 if not kept in motion, the particles in suspension would settle in a short time 

 at the bottom of the pipette and thus interfere with the accuracy of the results. 

 The amount of dilution varied with the age of the cheese from 750,000 to 

 100,000 parts of sterile water to one part of -cheese. The plates were levelled 

 on a nivellating apparatus, cooled with ice, and subsequently placed in a cool 

 incubator at 20 degrees €., where they remained till all development had ceased. 

 The colonies were counted by means of a Jeffets counter; and computations 

 were made therefrom. 



De Freudenreich's method of obtaining liquefying germs by making surface 

 •cultures from the last dilution was occasionally used. 



As previous work upon the bacterial flora of cheese had failed to show any 

 obligate anaerobes, no anaerobic methods of culture were used. 



Bacteria Found. 

 The bacteria found in the cheese at Guelph are divided into four classes: 



