2. Grain may become infected with poisonous fungi, e.g. ergot.
3. Plants or animals may feed upon materials harmless to them, but which render them poisonous to man—birds that have fed on mountain laurel are said to have proved poisonous to man.
4. During periods of physiological activity of certain of their glands, the flesh of some animals becomes poisonous to man; some fish, for example, are poisonous during the spawning season.
5. Food may carry infection by contamination with germs, e.g. typhoid bacilli in milk.
6. The animal may suffer from a specific disease, and it may be transmitted to man, e.g. tuberculosis.
7. Foods may be contaminated with bacteria which produce poisons either before or after the food has been eaten.
8. The food may be infected with parasites or their ova, and which develop in the individual who partakes of it, e.g. trichiniasis.
In cases in which the poison has been added or preformed, the symptoms of poisoning come on almost immediately or within a short space of time; there may, however, in the latter, be a delay in the appearance of the symptoms in instances where the bacterial poison is formed subsequent to the ingestion of the food. This delay is bordering on the nature of a true infection. In those cases when the bacteria have been present in the animal before, or develop in it subsequent to its death, and which develop in the person who eats it as food, symptoms may not come on for some time; the condition is a true infection, and there may be an incubation period over six or seven days.
Meat Poisoning
(Kreotoxismus)
Apart from those cases of poisoning following the ingestion of food to which poison has been added, or from meat affected by parasitic disease, there have occurred outbreaks of serious illness following the partaking of meat. Vaughan, in the Twentieth Century Practice of Medicine, vol. xiii. p. 20, holds that “there can scarcely be any difference of opinion on the following points: (1) With fresh food to act upon and with normal gastric juice to act, the process of peptic digestion proceeds without the formation of any harmful substance. (2) With putrid food, containing poisons to start with, the most active digestion does not guarantee the destruction of those poisons. (3) With even the best of food, peptic digestion may proceed so slowly and imperfectly that during the process poisons may be formed by bacterial agencies.” During the process of decomposition of meat and other albuminous foods by bacterial agency, certain poisonous substances are formed prior to the production of the ptomaines or bacterial alkaloids. These are known as toxalbumoses and enzymes; they are unstable bodies, they cannot be obtained in a crystalline form, and their composition is not fully understood. They give certain reactions with a few group reagents, but they are recognised only by their effects upon living animals. As decomposition advances the more stable alkaloids are formed, but those which are poisonous, like the toxalbumoses, are readily converted by further processes of putrefaction or by chemical means into innocuous bodies. Toxins is the general term used in toxicology for these poisonous substances formed from animal tissues.