STREPTOCOCCI 



147 



the surface usually produces the necessary conditions. The 

 method of Savage ^° is the most suitable with regard to the 

 quantities of the sample to be tested. He suggests using ten 

 tubes and placing 2 c.cms. in each tube, but this quantity may 

 of course be varied in accordance with the nature of the sample. 

 It is decidedly preferable to use a number of tubes containing 

 small amounts of milk than only a few tubes containing larger 

 amounts {vide supra). After two days incubation the tubes are 

 examined for the ^' enteritidis change '' which is indicated by a 

 complete separation of the curd and the production of acid, 

 the latter being easily detected by litmus solution. As other 

 organisms, such as B. butyricus, give this reaction, it is not to be 

 entirely relied upon, but these organisms are mainly non- 

 pathogenic and may be differentiated by injecting 1 c.cm. of 

 the whey subcutaneously into a guinea pig. 



Using ten tubes containing 2 c.cms. each, the most probable 

 number of spores present in 100 c.cms. of sample for each pos- 

 sible result is given in the Table LVIII, which is adapted from 

 McCrady's results.^ 



Table LVIII 



3. Streptococci. Cow manure contains 100,000 to 10,000-, 

 000,000 streptococci per gram, and the estimation of these 



