The association between carcinoma of the bronchial tree and cigarette smoking has been increasingly discussed in recent years, and a voluminous literature has appeared on the subject. Concerning the immediate action of the smoke on the respiratory pathways, on the other hand, particularly in regard to mucus flow and ciliary beating, the literature is comparatively scanty. Proetz1,2 demonstrated on animals that smoking produces a deposit of tar on the mucosa. In a series of three papers, Hilding3-5 discussed the same question, but from more general as well as from specialized aspects. After studying the smoking habits of human subjects, he pointed out that these vary so widely that the number of cigarettes smoked is not a reliable measure of the smoke intake. The size of the smoke intake also differs very considerably according to whether the cigarette smoke is inhaled or only taken into the mouth.
Hilding further