8 PROVISIONAL METHODS FOR ANALYSIS OF FOODS. 



(a) TRICHINAE. 



Pork, and sausage containing pork, which has caused sickness should be examined 

 at once for trichinae. a 



(b) POISONOUS METALS. 



The poisonous metals arsenic, antimony, tin, lead, copper, and zinc are to be con- 

 sidered. It should be borne in mind, however, that food poisoning from metals is 

 extremely rare compared with the causes mentioned under bacterial products. 

 It is furthermore not uncommon to find minute amounts of tin or lead in canned 

 meats or other canned food, and the accidental development of toxic properties in 

 such canned goods can not stand in any causal relation to such minimal amount of 

 metals. A single small dose of copper, lead, tin, or other metal need not in itself 

 cause any unpleasant effect, but continued dosing with such small amounts may in 

 the end give rise to disturbances. Several instances of this kind may be mentioned. 

 Vaughan, some years ago, found the cattle in a Western mining region to be dying 

 off because the stream from which they drank received the washings from a 

 hydraulic mining camp. An investigation showed that both arsenic and antimony 

 were present in solution as well as in suspension. Again, a garrison stationed on 

 an East Indian island was obliged to use exclusively water stored up in a galvan- 

 ized iron tank, with the result that chronic gastroenteritis developed in nearly every 

 man. The experience with arsenic in beer in Manchester is very recent. Several 

 hundred cases of chronic peripheral neuritis followed the continued use of beer con- 

 taining minute amounts of this poison. On the other hand, acute poisoning from 

 metals added intentionally or by mistake to foods are too well known. The amount 

 of poison in such cases is such as to render the whole matter easy of solution. 



From what has been said it is evident that poisonous meats could only under the 

 most exceptional conditions owe this property to metals. A chemical examination, 

 beyond revealing the merest traces of such metals as tin or lead, would mean noth- 

 ing. More than that, such an examination requires a relatively large amount of 

 material, and it not infrequently happens that the chemist hastens on with his chem- 

 ical examination, to which he subjects all or nearly all of his material, so that when he 

 attains a negative result scarcely any of the original substance is left for examination 

 along other lines. For the determination of heavy metals, proceed as directed under 

 vegetables (p. 52). 



(C) BACTERIAL PRODUCTS. 



The vast majority of all food poisonings are due to the invasion of the food by bac- 

 teria. The mere fact that bacteria are present in a meat is not evidence that such food 

 is poisonous. Many, in fact most, of the bacteria which invade food are incapable of 

 producing poisons, but they may grow and multiply and give rise to observable decom- 

 position changes. Such changes can be spoken of as simple decomposition due to 

 invasion by nonpoisonous bacteria. When, however, poison-producing germs develop 

 in the meat, then as food it becomes poisonous. It is a noteworthy fact that a food 

 may be highly poisonous without any visible indication of decomposition. In other 

 words, odor and taste are not always reliable guides as to the innocuousness of a food. 



The toxicogenic germ present in a food may be such that it can not grow in the 

 body, and hence it is obvious that the poisonous effects which are observed are due 

 to the poison which the germ had elaborated while growing in the meat. Such 

 poisonings are pure intoxications. Another type of germ not only grows in the meat 

 where it makes some poison, but it can also grow in the body, and as a result it con- 

 tinues to elaborate such poison for some time after being ingested. And, lastly, a germ 

 may be present which can not grow at ordinary temperature, but does grow in the 



Fisch6der, Leitfaden der praktischen Fleischbeschau; Ostertag, Handbuch der Fleischbeschau; 

 Walley, A Practical Guide to Meat Inspection. 



