146 MANUAL OF BACTERIOLOGY. 



Poisoning with milk, ice-cream or cheese is not rare, as 

 is well known. There are many records of whole compa- 

 nies of individuals having been taken violently ill after 

 having eaten one of these foods from the same source of 

 supply. The symptoms in such cases resemble those pro- 

 duced by irritant mineral poisons such as arsenic : nausea 

 and vomiting, vertigo, dryness of the mouth, sense of burn- 

 ing and constriction in the throat, difficulty in swallowing, 

 cramps and griping pain in the bowels, constipation or 

 diarrhea, general prostration or even collapse. Vaughan 

 isolated from poisonous cheese a ptomaine which he called 

 tyrotoxicon. It appears, however, that other toxins may 

 be present in cheese, and that tyrotoxicon is a somewhat 

 rare poison. Vaughan believes that bacteria of the colon 

 group play an important part in producing poisons in milk 

 and cheese. 



To prevent the alteration by bacteria of milk intended 

 to be the food of infants, the practice of sterilizing milk 

 has been largely in vogue. Unfortunately, during steriliza- 

 tion the milk undergoes some kind of alteration which 

 makes it disagree with certain infants. Furthermore, 

 among the organisms which would be likely to contam- 

 inate milk the bacilli of hay and potato, whose spores are 

 so excessively resistant, would be prominent, and they are 

 not killed by any process to which the milk intended for 

 an infant's consumption could possibly be subjected in the 

 household. Least of all can sterilization be expected to 

 purify milk in which bacterial poisons are already formed. 



The process called pasteurization is designed, not to ster- 

 ilize the milk completely, but to destroy the vegetative 

 forms of bacteria, and to destroy the ordinary pathogenic 

 bacteria with which the milk might possibly be contami- 

 nated. 1 The milk is subjected to a temperature of only 



1 See Journal of Experimental Medicine, Vol. IV., p. 217. "The Ther- 

 mal Death-point of Tubercle Bacilli in Milk," etc., by T. Smith. 



