366 Lee 



(b) -Remote Effects. — Rabbits were used for this experiment, because 

 they are known to be very susceptible to changes in the arterial system. 

 Two were made to inhale tobacco smoke regularly for about fifteen to twenty 

 minutes on alternate days throughout a period of five months. Two 

 methods were used. In the one a mask was fitted over the mouth and nose 

 of the animal and, with the apparatus already described, through which the 

 supply of both air and smoke could be regulated, the smoke from mild 

 cigarette tobacco was directed into the mask. A very dilute mixture was 

 at first given, but as the animal became accustomed to the treatment the 

 percentage of smoke was increased. The second method consisted in 

 placing the animals in a small chamber with inlet and outlet valves ; one 

 side of the chamber was of glass, to enable observations to be made, and 

 through this chamber smoke in varying quantities was passed continuously. 

 The latter method was chiefly employed. Whilst the animals were inhaling 

 the smoke, it was noticed that salivation was present, but no other changes 

 from their normal condition appeared. On being removed from the chamber, 

 for the ensuing three or four minutes they appeared lethargic, although 

 their reflex sensibility was somewhat heightened. At the end of five 

 months each animal had received about seventy inhalations of tobacco 

 smoke ; during this period they had increased in weight, as did the control 

 animal, and, as far as one could see, had suffered in no way, for they took 

 their food and behaved as normal rabbits, and during the later inhalations 

 showed no objection to the process. 



We now know that any substance which has the power of raising blood - 

 pressure suddenly and to any considerable extent, say 30 or 40 mm. Hg, 

 tends to injure the aorta. This has been shown by Harvey (5) in this 

 laboratory. Harvey raised the blood -pressure by compressing the ab- 

 dominal aorta, thus excluding all the hypotheses and speculations which 

 have been made suggesting that the " irritation " of the drug causes the 

 arterio-sclerosis observed. Moreover, irritant drugs which do not raise 

 blood -pressure do not cause arterial disease. 



We may, therefore, assume that if the smoking to which these animals 

 were subjected was capable of raising the blood-pressure to any considerable 

 degree, signs of arterial degeneration may be expected. 



Rabbit B was killed A few miliary patches were visible in the ascend- 

 ing aorta, and also a small plaque in that sinus of Valsalva which does 

 not give ofl" a coronary artery. The lungs showed some congestion, but 

 no consolidation, and the bronchial glands were normal. In the spleen 

 was an old infarct. The kidneys were normal. 



The aorta was prepared for microscopical examination ; portions of it 

 were hardened in formalin and dehydrated in a series of alcohols of in- 

 creasing strength up to 100 per cent.; they were cleared with chloroform, 

 and embedded in paraffin. Sections were cut and stained with : — (a) 

 acid hsematoxylin (Ehrlich) and aqueous eosin, or with picric acid fuchsin 

 (Weigert's modification of Van Giesen); (b) acid orcein (Unna-Taenz^r 



I 



