In his experiments Fullerton used tobacco juice obtained from the human mouth by chewing plug tobacco. He also used a solution of smoke obtained from a well seasoned pipe. These were first thoroughly sterilized in order to obtain a pure natural mixture of tobacco and saliva. Cultures of well-known species of bacteria were made using every laboratory precaution so as to obtain accurate results. Specimens of these bacterial cultures were then submitted to the action of the tobacco juice. It was found that exposure for one hour killed or rendered innocuous 15 to 98 per cent of the bacteria; exposure for 24 hours acted similarly on from 84 to 100%. Dr. Fullerton gives his opinion, from his results, that it seems that a pipeful of tobacco was more toxic to bacteria than one chew; but chewing tends to loosen retained food particles, foci of bacteria, etc., and much of this is ejected from the mouth. Fullerton's work agreed very well with the results obtained by other workers in the same line of investigation. In Miller's _Micro-organisms of the Human Mouth_, p. 246, it is stated that the organisms of the mouth lead only a miserable existence in a mixture of an infusion of tobacco, sugar and saliva; and that the smoke of the last one-third or the first one-fourth of a Colorado Claro cigar sterilized ten cubic centimeters of beef extract solution which had been richly inoculated with bacteria from decayed teeth. Arnold, _Lancet_ (London, 1907) reports similar experiences with some of the most virulent types of infective bacteria. Both nicotine and its derivative pyridine as well as the tarry oils resulting from tobacco distillation are strong and effective disinfectants; and formaldehyde, one of the most powerful germicides known, is so formed. Trillat, _Annales de l'Institut Pasteur_ (Paris), Vol. 19, p. 722, shows that 100 grams of pipe tobacco will yield .063 grams and 100 grams weight of cigar .118 grams of formaldehyde. Also that a dilution of 1/1000 formaldehyde is germicidal to all bacteria although it has very little deleterious effects on man.