228 EXAMINATION OF POISONOUS FOODS 



made except in a properly equipped laboratory. It is our purpose 

 to briefly point out the methods that may be followed, and in doing 

 so we take it for granted that the one who attempts work of this 

 kind is already familiar with the ordinary tecbnic of bacteriological 

 research. The line of procedure will vary somewhat with the kind 

 of food to be examined, the form in which it has been prepared, and 

 the quantity supplied the analyst. All samples should be examined 

 with as little delay as possible after the article has become the object 

 of suspicion. When delay is unavoidable, farther bacterial growth 

 should be retarded in the meantime as far as possible ; not by anti- 

 septics, but by low temperature. Microorganisms not present at the 

 time of the supposed poisoning may be accidentally introduced, or 

 non-toxicogenic bacteria may multiply to such an extent that the 

 detection of the harmful organism is rendered impossible. 



As a rule, the quantity of the food supplied the analyst is not 

 sufficient to allow of the detection or the isolation of the chemical 

 poison directly. To try to find the toxin in a few ounces of cheese 

 or a small bit of meat by direct extraction, is a task that would be 

 undertaken only by one quite ignorant of the nature of these poisons. 

 In all but exceptional instances, where many pounds of food are 

 supplied, the portion that reaches the laboratory can only be re- 

 garded as the bearer of the germ to the activity of which the poison 

 is due. This germ must be detected, isolated, grown in pure cul- 

 tures, and its toxicogenic properties demonstrated upon the lower 

 animals. It should be clearly understood that the most thorough 

 study of the morphological characteristics of the germ and of the 

 chemical properties of the poison will not suffice without an 

 accompanying determination of the toxicological action of the 

 culture. The infectious nature of the bacterium should also be 

 studied. 



It should always be borne in mind that the article of food has 

 probably been through several hands, some of which may not have 

 been germ-free. In the examination of pieces of meat and cheese, 

 the surface should be sterilized with a broad, heated knife or other 

 piece of iron. It has been shown that bacteria deposited on such 

 surfaces penetrate slowly. Then with other sterilized knives, sec- 

 tions should be made, and one or more small bits taken from the in- 

 terior should be placed in sterilized bouillon, milk or other culture 

 medium. Not less than a dozen tubes should be inoculated in this 

 way. Three of these should be grown aerobically at ordinary tem- 

 perature ; three anaerobically at the same temperature ; three aero- 

 bically at 37° and three anaerobically at 37°. Some of the toxico- 

 genic germs grow best at relatively low temperature (20° to 25°) 

 and faU to develop at 37°. Others have their optimum growth at 

 the last mentioned temperature. Some develop only when the air is 

 excluded, and others only when freely supplied with air. 



