class="smcap">Seasonal Distribution of Food Poisoning Cases, 1914-15 (Group, Family, and Individual)

There is no very striking seasonal incidence apparent in the figures here gathered (Table II). The warmer months seem to have a slight preponderance of cases, but general conclusions from such data are hardly warranted.

VARIOUS KINDS OF FOOD POISONING

Cases of poisoning by articles of food may be distinguished as: (1) those caused by some injurious constituent in the food itself, and (2) those caused by a peculiar condition of the individual consuming the food, by virtue of which essentially wholesome food substances are capable of producing physiological disturbance in certain individuals. The latter group includes persons, apparently normal in other respects, who are more or less injuriously affected by some particular article of diet, such as eggs or milk, which is eaten with impunity by all normal individuals. This is the so-called food sensitization or food allergy.

Food poisoning, as more commonly understood, is due to the composition, contents, or contamination of the food itself. It is not within the scope of this book to consider any of those cases in which definite poisonous substances are added to food with criminal intent. The term food poisoning is here taken to include the occasional cases of poisoning from organic poisons present in normal animal or plant tissues, the more or less injurious consequences following the consumption of food into which formed mineral or organic poisons have been introduced by accident or with intent to improve appearances or keeping quality, the cases of infection due to the swallowing of bacteria and other parasites which infest or contaminate certain foods, and the poisoning due to deleterious substances produced in food by the growth of bacteria, molds, and similar organisms. As already pointed out, little is known about the relative frequency of occurrence of these different causes or the extent to which they are separately and collectively operative.

THE ARTICLES OF FOOD MOST COMMONLY CONNECTED WITH FOOD POISONING

In addition to the definitely poisonous plants or animals, certain everyday articles of food have been frequently associated with the more serious outbreaks of food poisoning. Meat in particular has been implicated so often that the term meat poisoning is used about as commonly as the term food poisoning in general discussions of this subject. Certain it is that the great majority of the best-studied and most severe outbreaks of food poisoning have been attributed on good grounds to the use of meat or meat products. Other animal foods, and especially milk and its derivatives, cheese and ice-cream, have likewise been held responsible for extensive and notable outbreaks.

Perhaps the most significant feature of food poisoning attacks is the frequency with which they have been traced to the use of raw or imperfectly cooked food. The probable interpretation of this fact will be discussed in the later chapters. Especially have the use of uncooked milk, either by itself or mixed with other food substances, and the eating of raw sausage brought in their train symptoms of poisoning in a disproportionately large number of cases.

Canned goods of various sorts have likewise been repeatedly accused of causing injurious effects, but the evidence adduced is not always convincing. The actual degree of danger from this source is far from being determined. The National Canners Association publishes in the annual report of the secretary a brief list of "libels on the industry" or instances in which canned foods of various sorts were regarded as the cause of illness. The 1916 report contains fifty-one cases of this character, none of which was considered by the investigator of the Association to be based on sound evidence. A still more searching investigation of all such cases would seem to be desirable, not with a view to incriminating or exculpating any particular product, but simply for the purpose of ascertaining and placing on record all the facts.

CHAPTER II

SENSITIZATION TO PROTEIN FOODS

The first introduction under the skin of a guinea-pig of a minute quantity of egg-white or other apparently harmless protein substance is itself without visible injurious effect, but if this is followed by a second injection of the same substance after an interval of about ten days, the animal will die in a few minutes with symptoms of violent poisoning. Whatever be the physiological explanation of the remarkable change that thus results from the incorporation of foreign protein into the body, there can be no doubt that the phenomenon known as protein sensitization or anaphylaxis is relatively common.[2] Sensitization to proteins came to light in the first instance through the study of therapeutic sera, and has been found to have unexpectedly wide bearings. It is now known that not only the rash and other symptoms which sometimes follow the administration of horse serum containing diphtheria antitoxin, but the reaction to tuberculin and similar accompaniments of bacterial infection, are probably to be explained on the principle of anaphylactic change. The sensitiveness of certain individuals to the pollen of particular plants (hay fever) is also regarded as a typical instance of anaphylaxis, accompanied as it is by asthma and other characteristic manifestations of the anaphylactic condition.

Among the reactions usually classed as anaphylactic are the occasional cases of sensitivity to particular food substances. It is a familiar fact that certain foods that can be eaten with impunity by most persons prove more or less acutely poisonous for others. Strawberries and some other fruits and some kinds of shellfish are among the articles of food more commonly implicated. Unpleasant reactions to the use of eggs and of cow's milk are also noted. The severity of the