_Toxin production._--The problem of the production of toxin by the bacteria of this group and the possible relation of the toxin to food poisoning has been much discussed. Broth cultures in which the living bacilli have been destroyed by heat or from which they have been removed by filtration contain a soluble poison. When this germ-free broth is injected into mice, guinea-pigs, or rabbits, the animals die from the effects. Practically nothing is known about the nature of the poisonous substances concerned, except that they are heat-resistant. They are probably not to be classed with the so-called true toxins generated by the diphtheria and tetanus bacilli, since there is no evidence that they give rise to antibodies when injected into susceptible animals. In the opinion of some investigators the formation of these toxic bodies by the _paratyphoid-enteritidis_ bacilli in meat and other protein foodstuffs is responsible for certain outbreaks and also for some of the phenomena of food poisoning, the rapid development of symptoms being regarded as due to the ingested poisons, whereas the later manifestations are considered those of a true infection. Opposed to this view is the fact that well-cooked food has proved distinctly less liable to cause food poisoning than raw or imperfectly cooked food. A large proportion of the recorded meat poisoning outbreaks are significantly due to sausages made from raw meat and to meat pies, puddings, and jellies. This is most likely because the heat used in cooking such foods is insufficient to produce germicidal results. In milk-borne epidemics also it is noteworthy that the users of raw milk are the ones affected. For example, respecting an extensive _B. enteritidis_ outbreak in and about Newcastle, England, it is stated: In no instance was a person who had used only boiled milk known to have been affected. Thus in one family, consisting of husband, wife, and wife's mother, the two women drank a small quantity of raw milk from the farm, at the most a tumblerful, and both were taken ill about twelve hours later. The husband, on the other hand, habitually drank a pint a day, but always boiled. He followed his usual custom on this occasion, and was unaffected.[76]