vi] THE BACTERIA OF MILK 113 



effective, as to render them also unsuited. fc All 

 authorities, however, unite in condemning the use of 

 preservatives for milk. 



( a ) The diseases which may be directly transmitted from the cow 

 to man are in addition to tuberculosis scarlet fever, diphtheria, 

 and foot and mouth disease. ( 6 ) A few dairy bacteria are occasionally 

 known to have pathological characters. Four of these are Bacillus 

 coli communis, Staphylococcus albus, Staphylococcus pyogenes aureus, 

 and Streptococcus pyogenes aureus. ( c ) It should be pointed out that 

 the actual number of bacteria in milk is of little significance. The 

 most wide variations have been found in the same milk under 

 different conditions. ( d ) Gessard has quite recently obtained several 

 distinct varieties of this organism by cultivating it under different 

 conditions. These varieties differed widely in the type of pigment 

 they produced. ( e ) Gessard's work, above referred to, seems to in- 

 dicate that, in order to produce the typical blue colour, the acid 

 must be lactic acid. ( f ) It is somewhat misleading to speak of red 

 milk and violet milk in the same category as blue milk. Blue 

 milk is a dairy infection which attacks the milk rapidly, and pro- 

 duces in a short time a very prominent pigment. In the case of 

 the other types mentioned the pigment is slow in appearing, some- 

 times a few days, and sometimes several weeks elapsing before it 

 makes its appearance to any appreciable extent. ( r ) Freudenreich 

 has recently disproved this theory of Hueppe's. He has succeeded 

 in separating the bitter-tasting material in a partially free condi- 

 tion, and finds it is not a peptone. (*) Up to the present time con- 

 siderably over 200 dairy bacteria have been described. (*) Up to 

 the present time about a dozen organisms are known to produce this 

 kind of fermentation. There are many other kinds of fermentation 

 in which butyric acid is produced as a by-product. ( / ) Alcoholic 

 fermentation of milk is so well recognised now that it has been 

 suggested to use whey for the formation of alcohol, by inoculating 

 it with the proper species of bacteria. (*) Recently it has been dis- 

 covered that potassium bichromate exerts a very important anti- 

 septic influence on milk, from '3 to '4 of a gramme per 500 cc. of 

 milk, it is stated, being sufficient. Quite recently also, formalin, 

 viz. a 40 per cent solution of formaldehyde, has been used with 

 great success as a preservative. 



