DISTRIBUTION AND HABITAT OF THE BACTERIA, 717 



favourable for a multiplication of facultative parasites ; 

 further, the nutrient substrata could scarcely be better 

 even if they were prepared for the artificial cultivations 

 of the pathogenic bacteria ; again, many articles of food 

 are solid, and thus it is not so easy for the saprophytes 

 to overgrow these bacteria. Milk, broth, and meat are 

 excellent nutrient substrata for typhoid and cholera bacilli, 

 and we cannot but suppose that these and similar patho- 

 genic agents, when they once reach the food, the vessels, 

 or washing-cloths, &c., either through the air, or from 

 the earth, or by contact, very readily multiply to such a 

 marked extent that the greatest dangers may result from 

 the use of such food. 



Not only the facultative parasites, which find here Obligatory 

 conditions particularly favourable for their development, P arasites - 

 but also the obligatory parasites can be carried to man 

 by the food, and especially those which (like the tubercle 

 bacilli) are infective for animals as well as for man, and 

 are at times introduced by the use of meat. 



The dangers on the side of articles of food can be 

 almost completely avoided by the mode of preparation 

 by sufficient boiling and roasting and by avoiding the 

 use of food which has been kept for a considerable time 

 after being cooked. But as we know, in all nations and 

 in all classes of the people part of the food is eaten in a 

 raw state, or after it has been kept for a long time, and 

 thus it contains numerous bacteria. The proportion of Local differ- 

 the whole food which is employed in such a dangerous 



condition is very variable, and differs according to the bacteria in 



, , i mi ^ i .-, the food. 



customs and manners of each people. Thus while in 

 Southern lands there is the greatest carelessness as 

 regards the food, even the larger portion of it being 

 used in a raw or half decayed condition, in other 

 regions there is such great care in the selection, treat- 

 ment, and preparation of articles of food that the danger 

 of this mode of infection is reduced to a minimum. 



Hence the number of bacteria in articles of food, and 

 the danger of infection resulting therefrom, is evidently 

 subject to marked local differences, and seasonal varia- 

 tions can also occur with equal frequency. Thus, in 



