192 



DIFCO MANUAL 



3. Only when two or more specimens have been cultured 

 can any reliability or prediction be obtained. 



4. The clinician must study enough cases by use of periodic 

 laboratory data to establish in his own mind the value or 

 significance for the purpose intended. 



Snyder^ tabulated the correlation between the Snyder colorimetric test and 

 Lactobacillus counts on specimens of saliva collected routinely: 



Colorimetric Change (hours) 



To rehydrate the medium, suspend 65 grams Bacto-Snyder test Agar in 1000 

 ml. cold distilled water and heat to boiling to dissolve the medium completely. 

 Distribute in tubes and sterilize in the autoclave for 15 minutes at 15 pounds 

 pressure (121°C.). Final reaction of the medium will be pH 4.8. 



One pound of Bacto-Snyder Test Agar will make 7 liters of medium. 



1 J. Dental Res., 19:349:1940. * Grossman: Root Canal Therapy, and Edition: 



3 J. Ana. Dental Assoc, 28:44:1941. 273:1946. 



8 Dental Items Int., 49:589:1937. ^ Personal Communication, 1948. 



BACTO 



LITMUS MILK 



DEHYDRATED 



(B107) 



Bacto-Skim Milk 100 g. 



Bacto-Litmus 0.75 g. 



Bacto-Litmus Milk is recommended for propagating and carrying stock cul- 

 tures of the lactic acid bacteria associated with dairy products, and also for 

 determining the action of bacteria, upon milk. 



Milk has been used for the propagation and study of microorganisms since 

 the beginning of bacteriology. In addition to its being an excellent substrate for 

 propagating the lactic acid bacteria commonly associated with dairy products, 

 milk may be employed as a differential medium for bacteria on the basis of 

 lactose fermentation, caseolysis, and casein coagulating properties. 



The usefulness of milk in the study of bacteria is increased by the addition of 

 suitable indicators. Among the many indicators employed litmus has perhaps 

 enjoyed the widest usage. Litmus has the advantage of being readily reduced by 

 certain bacteria. This reduction of the litmus is useful as a differential aid. 



To rehydrate the medium, dissolve 105 grams of Bacto-Litmus Milk in 1000 

 ml. of distilled water. Distribute in tubes or flasks as desired and sterilize by auto- 

 claving for 15 minutes at 15 pounds pressure (121°C.). During the sterilization 

 period the litmus is reduced to the colorless leuco base, taking on color as the 



