[26] _Jour. Infect. Dis._, III (1906), 191. [27] _Jour. Amer. Med. Assoc._, LXIV (1915), 1230. [28] W. W. Ford, "Plant Poisons and Their Antibodies," _Centralbl. f. Bakt._, I Abt., Ref., LVIII (1913), 129 and 193, with full bibliography. [29] A. H. Clark, _Science_, XLI (1915), 795. [30] See W. M. Kerr, _U.S. Nav., Monthly Bull._, VI (1912), 401. [31] _Ibid._ CHAPTER IV MINERAL OR ORGANIC POISONS ADDED TO FOOD Well-known mineral or organic poisons--"chemical poisons"--sometimes find their way into food, being either introduced accidentally in the process of manufacture or preparation, or being added deliberately with intent to improve the appearance or keeping qualities of the food. ARSENIC So powerful a poison as arsenic has been occasionally introduced into food by stupidity or carelessness. Arsenic has been found by English authorities to be generally present in food materials dried or roasted with gases arising from the combustion of coal, and in materials treated with sulphuric acid during the process of preparation. In both cases the source is the same: the iron pyrites, practically always arsenical, contained in the coal or used in making the sulphuric acid. A celebrated epidemic of "peripheral neuritis" in the English Midlands in 1900 was traced to the presence of dangerous quantities of arsenic in beer. About six thousand persons were affected in this outbreak and there were some seventy deaths. The beer coming from the suspected breweries had all been manufactured with the use of brewing sugars obtained from a single source, and these sugars were found to have been impregnated with arsenic by the sulphuric acid used in their preparation, some specimens of the acid containing as much as 2.6 per cent of arsenic.[32] The use of glucose, not only in beer, but as an admixture or adulterant in jams, syrups, candies, and the like, is open to serious objection unless the glucose is known to have been prepared with sulphuric acid freed from arsenical impurity. In fact, the use of any food material prepared by the aid of sulphuric acid is permissible only in case arsenic-free acid is employed.[33] ANTIMONY The cheaper grades of enameled cooking utensils in use in this country contain antimony, and this is dissolved out in noteworthy amounts in cooking various foods.[34] The rubber nipples used for infants' milk bottles also sometimes contain antimony.[35] Although the poisonous qualities of antimony are well known, there is little information about the toxic effect of repeated very minute doses. Recognized instances of chronic antimony poisoning are very rare. Further investigation is needed. LEAD