THE GENERAL NATURE OF DIET 169 



labor is less fatiguing. The same action is often noticed as regards 

 muscular exertion. Tobacco is indeed often of great benefit in this 

 fatigue-abolishing way to hunters, lumbermen, soldiers, and others who 

 are liable to be obliged to undergo long periods of exertion. This 

 sedative effect on the thoughts and fears and worries of life is the source 

 of one of tobacco's benefits to humanity. It becomes, in these days of 

 hurried eating especially, a conducer to good digestion by tending to 

 make pleasant a quiet untroubled hour or half-hour after a meal, espe- 

 cially as the stimulating action on the mind makes toward sociability. 

 In having thus the double and seemingly almost contradictory effects of 

 quieting hurried anxiety and yet of stimulating mental action, tobacco 

 stands closer to opium than does any other substance known. The action 

 differs from opium's, however, in that it is the intellect and not alone 

 the imagination that is stimulated by tobacco, while the sedative effects 

 of the two plants are very similar, although that of opium is very much 

 more powerful. In combination with coffee, tobacco exerts a very strong 

 stimulation on the mind, sleeplessness being a frequent consequence. 



The circulation and especially the heart is more strongly and injuriously 

 influenced by the frequent taking of too much tobacco than any other 

 system of the organism, for the rhythm of the heart is deranged by 

 its excessive use and made irregular both in the force and the time 

 of the heart-beats. This, the "tobacco-heart," is the most common 

 effect of excess, but the results of its continuance are not cumulative to 

 any considerable extent (as are those of alcohol and opium), and pass off 

 in a relatively short time when the habit is broken. The immediate 

 action of nicotine on the heart and peripheral vessels is not definitely 

 known, the large number of experiments on various sorts of animals 

 being to our present understanding contradictory. 



Both the power and the disposition to do muscular work are un- 

 doubtedly lessened by the absorption of these alkaloids an effect of 

 which the physiological explanation is not as yet at hand. It is 

 apparently a matter either of neural or of muscular metabolism, 



On the mucous membrane of the mouth and throat tobacco sometimes 

 exerts an injurious drying-action, leading to chronic inflammation of a 

 mild type. Its nauseating effect is reflexly caused probably by stimula- 

 tion by the nicotinized saliva of the unaccustomed nerve-endings in the 

 stomach-wall. Were this nausea not so sharp and painful to the youth- 

 ful mind, there would be even more smokers than there are. Nicotine 

 is said to cause an increase in the urinary excretion of uric acid and of 

 phosphoric acid; it does not affect the respiratory exchange. Excessive 

 use of tobacco produces insomnia and great nervous irritability, besides 

 the functional cardiac irregularity already noted. Each user of the herb 

 must determine for his own particular organism the limits beyond which 

 needless injury is done him. 



To the evolving and unstable nervous systems of childhood and youth 

 all of these substances usually known as stimulants are, of course, 

 particularly poisonous. 



