"Comparatively few studies have been made of the effects of tobacco smoking on human beings; and such as have been made fail to state if the tobacco used or the smoke produced was examined for nicotine or its congeners. The absence of an examination necessarily causes some doubt in the causative faction of the phenomena. Some authors are rather inclined to conclude that nicotine alone is the pathogenic factor in tobacco smoking, but since the presence of nicotine _per se_ in tobacco smoke is debatable and since other toxic substances are demonstrable, it would seem as if the whole subject still remained open for investigation." The nicotine contained in ordinary tobacco, according to many authors, ranges from about 1 to 8 or 9 per cent. Lee's investigation (_Journal of Physiology_, 1908, p. 335) found that about half of the total nicotine was present in the smoke--according to Lee the pyridin seemed to be entirely without influence. Lehmann (_Archiv für Hygiene_, 1909, p. 319) found that from 80 to 90% of the total nicotine in a cigar or cigarette was to be found in the smoke. He found also that in the case of cigars about 10 to 18% of the nicotine in the smoke is absorbed by the smoker and that cigarette smoke absorbed by the smoker contains a less proportion of the nicotine in the tobacco than is the case with cigars. The general opinion is, however, that about one-seventh of the nicotine in the tobacco will be found in the smoke. Entirely at variance with these results are those obtained recently by A. D. Bush, M.D., Instructor of Physiology in the University of Vermont (New York _Medical Journal_, March 14, 1914), and those obtained in the laboratory investigation by the London _Laucet_. Bush made long and extensive investigations on the effects of tobacco smoking and criticised the results of previous workers. He shows very clearly that in many cases the conclusions drawn by them as regards nicotine contained in tobacco smoke are either entirely erroneous or that the deductions made from the investigations were not warranted by the facts observed. He points out the fact that most writers on the subject have overlooked the fact of the great discrepancy between the possible effects arising from the administration of the amount of nicotine in a cigar and the actual effect produced on the smoker of the cigar. He asks this pertinent question: "If a cigar contains 0.085 grains nicotine, and if one-seventh of the nicotine of the tobacco is present in the smoke and if but .004 grains is capable of causing death, why does the smoker not absorb enough nicotine to cause his demise?"