246 The Bacteriology of Foods 



always be treated with the greatest care to prevent such contamina- 

 tion, as saprophytic bacteria produce chemical changes in the milk, 

 such as acidity and coagulation, which destroy its usefulness or 

 render it dangerous as food for infants and invalids. Where the 

 necessary precautions are not or cannot be taken, Pasteurization of 

 the milk as soon after its reception as possible may act as a safeguard. 



The student interested in the sanitary relations of milk cannot 

 do better than refer to Bulletin No. 35 of the Hygienic Laboratory, 

 Washington, D. C, 1907, "Upon the Origin and Prevalence of 

 Typhoid Fever in the District of Columbia," and to Bulletin No. 41 

 of the same laboratory, upon " Milk and its Relation to the Public 

 Health" (1908); also to the "Bacteriology of Milk," by Swithinbank 

 and Neuman, New York, E. P. Button & Co., 1903. 



Meat from tuberculous animals might cause disease if eaten raw 

 or but partially cooked. As cooking suffices to kill the organisms, 

 the danger under ordinary conditions is not great. Moreover, 

 tuberculosis rarely affects the muscles, the parts usually eaten. 



Butter made from cream derived from tuberculous milk may also 

 contain tubercle bacilli, as has been shown by the researches of 

 Rabinowitsch. * 



Foods may become polluted with bacteria in a variety of ways 

 that will suggest themselves to the reader. The common source is 

 dust, which is more or less rich in bacteria according to the soil from 

 which it arises. The readiness with which raw foods, such as meats, 

 milk, etc., can be thus contaminated in the barnyard, dairy, slaughter- 

 house, and shop, teaches but one lesson — that the greatest cleanli- 

 ness should prevail for the sake of the dealer, whose goods may be 

 spoiled by carelessness, and the consumer, who may be injured by 

 the food. 



Any food may carry infectious organisms upon its surface, such 

 organisms being derived from the hands of the dealer, from dust, 

 from water, as when green vegetables are sprinkled with impure 

 water to keep them fresh, or from other sources. 



The cleanliness of the merchant and the protection from contami- 

 nation that he bestows upon his goods should be taken into consid- 

 eration by his customers. 



Shell-fish, especially oysters, seem to be common carriers of infec- 

 tion, especially of typhoid fever. The oysters seem to be contami- 

 nated with infected sewage carried to their beds. It is not yet 

 satisfactorily determined whether typhoid bacilli multiply in the 

 juices in the shells of the oysters or not, but a number of epidemics 

 of typhoid fever have been very conclusively traced to the consump- 

 tion of certain oysters at a definite time and place. As cooking the 

 oysters will kill the contained bacilli, the prophylaxis of disease in 

 this case is very simple. 



* "Deutsche med. Wochenschrift," 1900, No. 26; abstract in the "Centralbl. 

 f. Bakt.," etc., 1901, xxix, p. 309. 



