FOKESTS AS SITES FOE SANATOEIA 25 



tions are so dilute that their effect is more psychical than 

 physical " is not scientific. 



Most people write of the turpentine emanations of pine 

 forests, but the large amount of resin and turpentine stored 

 in the wood and bark of the steins and branches is not 

 exhaled into the atmosphere, except in the case of wounds 

 or disease of the trees, which cause a flow of resin. The 

 odour of pine woods is due, in great measure, to a volatile 

 oil contained in the leaves. This is variable in composition, 

 containing pinene (the main or often sole constituent of 

 turpentine oil), sylvestrene, phellandrene, and a notable 

 percentage of bornyl acetate, which gives to it a character- 

 istic odour. Pine-needle oil, produced by distillation, is a 

 clear odourless fluid used as a deodorant in baths, hospitals, 

 etc., and is sold all over the world for rheumatic com- 

 plaints (9). 



No scientific study of the odours of the air from a 

 therapeutic point of view has, I believe, ever been attempted. 

 We are, moreover, quite in the dark as to the curative effect 

 of change of air in many cases of illness, which is in our 

 ignorance ascribed to psychic causes. 



Two suggestions have been made in explanation of the 

 curative effects of the odours of pines on tubercular diseases 

 of the lungs. Dr. Horace Dobell relied on Kingzett's ex- 

 periments (10) on the oxidation of volatile oils under the 

 influence of air and moisture, when peroxide of hydrogen 

 and camphoric acid were produced, the former being a 

 powerful disinfectant and the latter an antiseptic. The 

 volatile oil exhaled by pines being converted into these 

 agents was supposed to render the atmosphere destructive 

 to bacteria. No such germicidal action of the air in pine 

 forests has, however, been proved to take place ; and Dr. 

 Dobell's theory is no longer tenable. 



The researches in phagocytosis carried on by Prof. 

 Hamburger (11) of Groningen University, Holland, possibly 

 afford an explanation of the therapeutic effects of the odours 

 of pine forests. He exposes on slides under the micro- 

 scope drops of blood which have been put into various 



