414 MICROBIOLOGY OF SPECIAL INDUSTRIES. 



engaging or continuing in occupations concerned with the immediate 

 preparation of food for consumption, particularly such occupations as 

 market-dairying, cooking, and serving food. Numerous serious epi- 

 demics have been traced to such sources in recent years. 



FOOD POISONING DUE TO THE GROWTH OF SAPROPHYTIC BACTERIA TN 



THE FOOD. 



Most food poisonings are due to food derived from perfectly healthy 

 and wholesome animals or plants, which has subsequently undergone 

 some bacterial decomposition giving rise to poisonous products. Our 

 knowledge of the specific causes of the poisonous changes is, however, very 

 incomplete, and on account of the difficult nature of investigation in this 

 field, some of the conclusions reached by careful men are still open to 

 question. The bacteria which have been most frequently identified with 

 various epidemics of food poisoning are the following: B. enteritidis in meat 

 poisoning; B. botulinus in meat and in sausage poisoning; B. paratyphosus 

 in poisoning with meat, chicken, shell-fish, and vegetables; B. coli in cheese 

 poisoning and in milk poisoning; B. vulgaris in meat and in vegetable food 

 poisonings. Doubtless other microorganisms, as yet unrecognized, play 

 an important part in many food poisonings, and there is reason to believe 

 that some of these important unknown forms are anaerobic bacteria. 



POISONOUS MEAT AND SAUSAGE. The flesh of a healthy animal is 

 ordinarily free from bacteria at the time of slaughter, and bacterial changes 

 must begin at the surfaces of the pieces of meat and gradually extend in- 

 ward . In diseased animals, b acteria more frequently circulate in the blood, 

 and the flesh may be contaminated throughout when the animal dies of the 

 disease or when it is slaughtered, not only with the specific germs of the 

 disease but also with bacteria derived from the intestinal tract of the ani- 

 mal. It is a matter of observation that the flesh of diseased animals is 

 more liable to undergo early putrefactive and poisonous changes than that 

 derived from healthy animals. Hashed meat is, of course, much more 

 prone to bacterial decomposition, because in it the bacteria have become 

 well distributed throughout the mass, and ideal conditions are provided 

 for the development of anaerobic as well as aerobic bacteria. Minced 

 chicken and chicken pie appear to be very frequent sources of acute 

 poisoning in the United States, and epidemics of sausage poisoning have 

 repeatedly occurred, especially in Germany. The bacteria found to be 

 concerned in these instances have been B. enteritidis, B. paratyphosus, 



