THE EXAMINATION OF MILK 415 



out perceptibly changing it, but they are both destroyed 

 when the lactic acid fermentation sets up. In addition to 

 the contamination with various pathogenic organisms which 

 may give rise to disease in man, milk is liable to attacks 

 of certain non-pathogenic bacteria which are the cause of 

 certain milk-diseases known as ' blue milk,' ' red milk,' 

 ' yellow milk,' ' bitter milk,' ' stringy milk,' ' slimy milk, 

 ' soapy milk,' and a number of others. 



The peptonising organisms were minutely investigated 

 and classified by Fliigge (Zeitschr. f. Hyg., xvii., pp. 272, 

 342). In general, they require many hours' boiling for 

 their destruction ; boiling for an hour, for instance, being 

 sufficient to destroy the lactic acid and butyric acid bac- 

 teria, but not the peptonising organism to which those of 

 bitter milk belong. Their development is greatly favoured 

 by warmth, so that they multiply with great rapidity at 

 room-temperature in summer time. It is not easy to 

 detect their action on milk with the eye, the commence- 

 ment of the peptonising giving at the utmost a thin, clear 

 layer under the cream. Experimentally, several of these 

 organisms have been shown to produce serious intoxica- 

 tion, and it is some organisms of this group which are 

 responsible for infantile diarrhoea. Their significance is 

 probably even greater than this fact implies, because, if 

 not sufficient to produce acute specific disease in adults, 

 they or their decomposition products in milk are liable to 

 set up digestive derangements which render the consumer 

 more accessible to other diseases of intestinal origin. 



Blue Milk. — This is a common disease of milk, and 

 consists of the formation of blue patches on the surface of 

 the milk, which condition may be produced in from twenty- 

 four to seventy hours, according to the temperature. 

 Steinhoff, as early as 1838, showed this disease of milk to 

 be infectious, and Fuchs, in 1841, stated that the disease 



