EXTRACT XIX. 



ON THE PHYSIOLOGICAL ACTION OF TOBACCO IN 

 THE VARIOUS METHODS OF ITS USE. 



WE have already advanced in a former study in con- 

 nection with the pneumatic or air spaces of the face and 

 head that these spaces constitute what may be called the 

 lungs of the head and face, inasmuch as an interchange 

 of gases seems permitted by diffusion and chemical action 

 or interchange through their thinly lined cavity walls, in 

 which the blood capillaries are distributed in much the 

 same manner as they are in the ultimate bronchial passages 

 and pulmonary vesicles of the lungs. 



The recognition of a provision near the great centre of 

 life, the brain, of a supplementary means of keeping pure 

 the blood circulating in its immediate vicinity and basal 

 neighbourhood, and within its supporting structures, if 

 not to a limited extent within the passages leading to and 

 from itself, may be regarded as of great importance on 

 account that these somewhat neglected spaces would conse- 

 quently be brought within the circle of the more vital 

 parts, and so have their condition as to soundness and 

 patency more enquired into by those engaged in their 

 clinical oversight, and their therapeutics, prophylactic and 

 curative, placed on a more definite and scientific basis. 



Flowing out of our study of this subject, the rationale 

 of the physiological effects of one of the most all-pervad- 

 ing habits of modern life and times, viz. smoking, and 

 inferentially all other ways of using tobacco, seems de- 

 ducible or, at any rate, more apparent. 



We have on many occasions asked devotees of the habit 



