V.—Milk has been a common carrier of disease. Cows eating the rhus toxicodendron get the “trembles,” and their milk produces serious gastric irritation in young children. The milk of goats fed on wild herbs or spurgeworts has produced severe disorders.
The milk of animals suffering from foot-and-mouth disease, although frequently drunk with impunity, occasionally produces inflammation of the mouth (aphthous ulceration). The milk derived from cows fed on grass from sewage farms is, per se, as wholesome as any other, and its butter has no more tendency to become putrid than that derived from any other source.
The great dangers in respect to milk are of its becoming mixed with contaminated water; or of its absorbing foul odours. The absorptive power of milk for any vapour in its neighbourhood, is shewn by exposing it in an atmosphere containing a trace of carbolic acid vapour: the milk speedily tastes of the acid.
Milk also tends to undergo rapid fermentative changes, especially in warm weather, or when tainted by traces of putrefying animal matter. Diarrhœa in children is frequently due to such a condition, or to the rapid decomposition of milk in an imperfectly cleaned bottle. Milk should always be boiled in warm weather; and it should never be stored in ill-ventilated larders, or where there is a possibility of the access of drain effluvia; nor ought it to be kept in lead or zinc vessels.
Epidemic diarrhœa has been ascribed by Klein to a microbe called the Bacillus enteritidis sporogenes. This is not killed by heating the liquid containing it to 80°C. for twelve to fifteen minutes, as is the typhoid bacillus and other non-spore-forming bacilli. In an outbreak of diarrhœa among the patients in St. Bartholomew’s Hospital, London, there was strong evidence that this microbe taken in rice pudding had caused the mischief. Eighty-four patients and two nurses were attacked, and the patients who had eaten rice pudding were almost exclusively attacked. A portion of this pudding after being kept twenty-four hours was found sour and acid. The Bac. enteritidis sporog. was found in it. Furthermore it was shewn that the temperature at which the rice puddings were cooked never exceeded 98°C., whereas the spores of this microbe withstand 100°F. a considerable time.
Very many epidemics of enteric fever and scarlet fever, and a smaller number of epidemics of diphtheria have been traced to contaminated milk. Usually in enteric fever the contamination of the milk was traced to the use of water “for washing the milk-cans,” derived from specifically polluted sources, and doubtless the water was the real source of the disease. In most of the milk outbreaks of scarlet fever, either there was scarlet fever in the dairy, or persons employed in the dairy were in attendance on patients suffering from the disease; but in an outbreak connected with a supply of milk from Hendon, it was suspected that a certain eruptive disease of the udders of the cow might have been the cause of scarlet fever in man, without infection from a previous case of the disease. This point is still sub judice.
Tubercular disease of the intestines and mesenteric glands may be produced by taking milk derived from tuberculous cows. This was proved in the case of calves (page [311]), and there are strong reasons for thinking that the same is true for infants, though doubt has been thrown by Koch on the communicability of bovine tuberculosis to the human being. The only safe plan is to sterilise the milk (page [13]).
VII.—Vegetable Food (especially greens) is indigestible if stale, and all mouldy vegetables are dangerous. Over-ripe and rotten fruit is liable to produce diarrhœa; but the diarrhœa prevalent in summer is due much less to this than to other decomposing foods, particularly milk.
Poisonous symptoms have been produced by the admixture of darnel (lolium temulentum) with flour.
The eating of damaged maize in Italy is the cause of an endemic skin disease, called pellagra, which commonly proves fatal.