SOURCi:S OF liACTERIA I\ MILK 



ti3 



spores. It is not difticult to destroy the sporeless cell by heat, 

 but the spores are \-er}- re>i.>tant to unfavorable Conditions. 

 The spore-bearing bacteria are difficult to kill; b(jilinLJ- for a short 

 time will not destroy them. Hammer is satisfied that thev are 

 destroyed by prolongerl boiling. Another method is to heat the 

 milk to destroy all the organisms in the vegetatiAX- stage, then 

 cool it to a temperature fa\Tjrable to growth and allow the spores 

 to develop into the vegetatiA'e stage, anrl again apply heat. In 

 this way milk can be rendered entirelv sterile. A sinele heating 



Fig. II. — The wrong and the right kind of a milli-pail. .4, the ordinar\- t>pe of 

 pail showing sharp angle Ijetween side> and b(jttom; B. the same pr(jperl\- 

 flushed with solder so as to facilitate thomugh cleaning. The lower figure 

 represents a joint a> ordinarily nade in tinware. The depression a affords 

 a place of refuge for bacteria from which thc\' are not readily dislodged. This 

 open joint bhould be filled completely with solder. (F'rom Bui. 62, Wis.) 



under pressure (fifteen minutes at 15 prjunds pressure) kills them 

 at once. 



It has been demonstrated by se\'eral in\-estigators that freshly 

 drawn milk is not a good medium for bacteria to de^"elop in. 

 In fact, seA'eral experiments seem tcj indicate that milk acts as a 

 germicide to certain \-arieties of bacteria. For instance, the 

 cholera germ is to some extent destroyed in fresh milk, but it is not 

 known to what extent. Organisms producing lactic acid check 

 the multipHcations of these pathogenic bacteria. This gemiicidal 

 property is said to be more or less common to all the animal 

 secretions. 



