508 BACTERIOLOGY. 



possibility of the presence of injurious metals, such as tin 

 or arsenic, should be conceded and a thorough examination 

 of a poisonous food should involve tests for the recognition 

 of such metals. On the other hand, the fact that a gram 

 or two of cheese, or a tea-spoonful of ice-cream, at -times, 

 causes pronounced illness would indicate that the poison 

 cannot belong to the group of metals. 



In the examination of poisonous meat and sausage the 

 possibility of the presence of trichinae should be clearly 

 borne in mind. A bacteriological examination will be of 

 no value unless the presence of these parasites is definitely 

 excluded. Repeated examinations should be made, and, if 

 possible, these should be controlled by the examination of 

 tissue known to contain trichinae. 



Having excluded the presence of metallic poisons and 

 the presence of animal parasites, as trichinae, then the 

 poison-producing bacteria that may be present should 

 receive attention. Food-poisoning from bacteria may 

 originate in any one of the following ways: 1. The food is 

 infected and the poison is generated exclusively be- 

 fore the food is taken. The organism in this case may be 

 considered as a true saprophyte endowed, however, with the 

 property of producing highly poisonous substances. Hence, 

 the intoxication will be directly proportional to the 

 amount of poison which is ready made in the food at the 

 time this was taken. 2. The infecting organism may 

 begin the elaboration of its poisonous products outside of, 

 and continue the same process inside the body. In this 

 case the organism is able to grow in the intestines, and may 

 even penetrate the organs and tissues. The illness has the 

 general characteristics of an acute infectious disease. 

 3. The illness may not result in the production of poisons 

 until the food is taken into the body. As an illustration, 

 milk or water infected with typhoid or cholera bacteria 

 may give rise in the one case to typhoid fever, and in the 

 other case to cholera. 



