Action of Tobacco Smoke 351 



sometimes colicky pains are felt in the abdomen, suggesting increased 

 peristalsis. 



These experiments strongly suggest that fall in blood-pressure is the 

 essential factor in the production of collapse, for all the symptoms of 

 collapse are such as are obtained from a sudden fall in blood-preasure. I 

 believe that these simple experiments amply confirm the hypothesis of 

 Crile (4), that shock and collapse are conditions resulting from a severe 

 fall in blood-pressure. 



In tobacco smoke there is only one constituent (nicotine) which has the 

 power of increasing blood-pressure appreciably, but there are many sub- 

 stances, such as the pyridine bases, which lower the pressure. During the 

 inhalation of tobacco smoke, the action of nicotine overshadows that of the 

 other constituents; the nicotine stimulates nerve cells, and for a time 

 exercises unchallenged its vaso-constrictor influence, with the accompanying 

 rise of blood- pressure. But a stage in smoking is reached when the 

 stimulation of nerve cells by the nicotine gives place under the same 

 influence to their depression, with resulting vaso-dilatation and a fall in 

 blood-pressure. This condition will be exaggerated by the other con- 

 stituents of the smoke, such as pyridine and collidine, whicii throughout 

 have been tending to lower blood-pressure. 



Tbe action, then, of tobacco smoke on man is exactly what might 

 be anticipated from a knowledge of the action of nicotine : while the 

 stimulation stage lasts the pressure is raised ; then, as the nerve cells 

 are depressed, the blood - pressure falls. But I have obtained plenty 

 of evidence of variations in the degree of idiosyncrasy for nicotine. 

 Thus, in comparing experiments 2 and 3, although the subjects were 

 very similar as regards their smoking habits — in fact, they were both 

 almost complete novices — yet the elder was much more affectod than the 

 younger, twice the quantity of smoke being required to produce a similar 

 effect in 3 as in 2. 



The second group is composed of moderate smokers, and tliis gj-oup 

 probably includes the majority of those who smoke regularly. Experi- 

 ments 5, 6, and 7 are typical examples. In these the blood-pressure rises 

 slowly, unlike those in the tirst group, where the rise is rapid ; the heifjht 

 to which the pressure rises, however, is about 10 nmi. Hg, and the 

 tendency is for the blood-pressure to continue rising slightl3% or at least to 

 maintain the higher level, whilst the smoking lasts. With the novice, on 

 the other hand, blood-pressure falls, and collapse ensues w;hilst smoking 

 is actually in progress. In these temperate smokers, after smoking has 

 ceased, the blood-pressure falls gradually to the normal, but shows no 

 tendency to move below that level. The whole effect, then, consists of 

 a small and gradual rise of blood-pressure lasting until the smoking 

 ceases. The rise in pressure is usually associated with some acceleration 

 of the pulse. 



Of course these experiments only show the effects of moderate smoking 



I 



