90 THE TYPES OF MILK BACTERIA. 



uct, is not as yet known. There is no necessity for further 

 reference to them here, because they never make themselves 

 apparent in dairy processes, and probably play no part in 

 general dairying. It is well to remember, however, that they 

 are commonly present in abundance and 

 that they may have some relation to the 

 cf^cP power of milk bacteria to produce diar- 

 oW* rheal diseases. 



Otfn 00 There are some other types of bac- 

 ff teria present with more or less con- 



Bactena with no effect * 



on milk, a, a bacterium ; stancy, but which, under ordinary cir- 

 B th cumstances, appear to be of no sig- 

 nificance. (i) There are present in 

 milk, apparently in all cases, certain species that are strictly 

 anaerobic and grow only in the absence of oxygen. These 

 organisms are not usually found by ordinary bacteriological 

 study, because they require special methods and special 

 apparatus for their detection. There is no reason for think- 

 ing that they grow in the milk under ordinary circumstances ; 

 certainly they do not produce any of the usual changes which 

 occur in milk. If they produce any action upon normal milk 

 we are not acquainted with the fact at the present time. It 

 is possible that they are associated with the intestinal troubles 

 attributed to milk, but this is purely hypothetical. It has 

 been thought that they may have something to do with the 

 changes that take place in butter, causing it to become 

 rancid, but this has been rendered doubtful in recent years. 

 Some of them undoubtedly produce butyric acid from milk 

 if they get an opportunity to grow sufficiently. So far as 

 known, these anaerobic organisms are of little significance in 

 the dairy since they grow slowly and rarely make themselves 

 evident. (2) A type of milk bacteria of which we know 

 little has the character of growing -only at high temperatures. 

 These are bacteria that will grow only .when the milk is 

 warmed to a temperature of about I4OF. Where they come 



