THE EXAMINATION OF MILK 323 



other two samples, which were more virulent, came from 

 dairies where there was more than one suspected cow, 

 and where the udders of some of the animals were visibly 

 tuberculous. 



Affected milk may not, under ordinary circumstances, 

 induce tuberculosis, owing to its not containing a sufficient 

 number of organisms to constitute a ' toxic dose,' but in the 

 case of persons rendered susceptible owing to disease or 

 weak health, or who have a constitutional predisposition to 

 consumption, the use of tuberculous milk constitutes a very 

 grave danger to health. 



Many other diseases are conveyed by the agency of milk. 

 According to Dr. Ernest Hart, fourteen epidemics of scarlet 

 fever and seven of diphtheria have been traced in this 

 country to the use of infected milk, as have also a number of 

 epidemics of typhoid fever and cholera. As already shown 

 (see p. 149) the typhoid bacillus and the cholera spirillum are 

 capable of rapid multiplication in milk, without 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. 



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 

 was caused by a microbe, which, however, he was unable 

 to cultivate owing to the imperfect bacteriological methods 



