The conspicuous frequency with which the consumption of raw meat provokes food poisoning has already been set forth and in large part explained by the occasional derivation of meat from animals infected with parasites harmful to man. The even greater culpability of raw milk is due to the fact that milk is not only, like meat, sometimes obtained from an infected animal, but that it is a particularly good culture medium for bacteria, and in the process of collection or distribution may become infected through the agency of a human carrier. Foods such as ice-cream that are prepared with milk are also often connected with food poisoning. It seems probable that illness caused by ice-cream is much more commonly due to bacterial infection than to poisoning with metals or flavoring extracts. The responsibility of these latter substances is entirely problematic.

Cases of cheese poisoning, which apparently are relatively numerous, are of quite obscure causation. Whether such poisoning is due more commonly to some original contamination of the milk, or to an invasion of the cheese by pathogenic bacteria in the course of preparation, or to the formation of toxic substances by bacteria or molds during the process of ripening which the cheese undergoes, is left uncertain in the majority of cases.

Shellfish poisoning from eating oysters, mussels, or clams is unquestionably caused in some instances by sewage contamination of the water from which the bivalves are taken, and in such cases bacilli of the typhoid or paratyphoid groups are commonly concerned. It is a disputed question whether certain recorded outbreaks of mussel poisoning have been due to bacterial infection or whether sometimes healthy or diseased mussels taken from unpolluted water contain a poisonous substance. In a similar way it is uncertain whether a certain marine snail (Murex bradatus), sometimes used for food, contains under certain conditions a substance naturally poisonous for man, or whether it is poisonous only when it is infected or when toxigenic bacteria have grown in it.

Potato poisoning has been attributed in some cases to bacterial decomposition of potatoes by proteus bacilli; in other cases, to a poisonous alkaloid, solanin, said to be present in excessive amounts in diseased and in sprouting potatoes. It is noteworthy that many instances of potato poisoning have been connected with the use of potato salad which had stood for some time after being mixed, so that the possibility of infection with the paratyphoid bacillus or other pathogenic organisms cannot be excluded. That solanin is ever really responsible for potato poisoning is considered doubtful by many investigators.

These examples are sufficient to show that in a considerable proportion of cases of alleged food poisoning there is a large measure of uncertainty about the real source of trouble. Although the trend of opinion has been in the direction of an increased recognition of the share of certain bacteria, especially those of the paratyphoid group, there is an important residue of unexplained food poisoning that needs further skilled investigation. It is one of the objects of this book to point out this need and to draw attention to the numerous problems that await settlement. The first step is the regular and thorough investigation of every food poisoning outbreak.

INDEX

FOOTNOTES:

[1] Tables [A] and [B] show that the "expectation of life" for adults of forty years and over is shorter in New York City now than it was thirty years ago ([Table A]), and that this increase in the death-rate in the higher-age groups is manifested in recent years in a wide area in this country ([Table B]). This increased mortality is due chiefly to diseases of the heart, arteries, and kidneys, and to cancer.

[TABLE A][1a]