[106] _Loc. cit._ [107] _Loc. cit._ [108] In the feces of a healthy pig (Kempner and Pollock, _Deutsche med. Wchnschr._, XXIII [1897], 505). [109] _B. botulinus_ does not develop in media containing over 6 per cent of salt and should not be able to grow in meat properly covered in brine made with 10 per cent of salt (Römer, _Centralbl. f. Bakt._, XXVII [1900], 857). [110] G. Landmann, _Hyg. Rundschau_, XIV (1904), 449. [111] Wilbur and Ophüls, _Arch. of Int. Med._, XIV (1914), 589. [112] _Phil. Jour. of Science_, IX (1914), B6, p. 515. [113] K. Blunt and C. C. Wang, _Jour. Biol. Chem._, XXVIII (1916), 125. CHAPTER IX POISONING OF OBSCURE OR UNKNOWN NATURE While many and diverse causes of food poisoning have been discussed in the foregoing pages, there remain certain affections definitely connected with food that are still of obscure or doubtful causation. MILKSICKNESS OR TREMBLES This disease, common to man and some of the higher animals, is characterized by a definite symptom-complex, the salient features being excessive vomiting and obstinate constipation accompanied usually by a subnormal temperature. Many cases result fatally. At the present time it is known to occur only rarely in some of the southern and central western states in this country, but during the period of pioneer settlement it was quite common in districts that are now seldom affected. A great many references to milksickness are found in the writings of the early travelers and physicians in the Middle West, one observer predicting that "some of the fairest portions of the West in consequence of the prevalence of this loathsome disease must ever remain an uninhabitable waste unless the cause and remedy can be discovered." In certain regions it is estimated that "nearly one-fourth of the pioneers and early settlers died of this disease." The mother of Abraham Lincoln fell a victim to this malady in 1818 in southern Indiana. The disease appears to be usually contracted in the first instance by grazing cattle or sheep that have access to particular tracts of land; "milksickness" pastures are, as a rule, well known locally for their dangerous qualities. Milksickness is communicated to man through the medium of raw milk, or butter and possibly of meat. Although some of the earlier observers make the statement that the disease is self-propagating and can be passed on without limit from one animal to another, later experiments cast doubt on this view.[114]