THE EXTERNAL ENVIRONMENT 253 



Opium and tobacco also affect the body. The principle of 

 opium is morphia, which acts as a narcotic. 



The active principle of tobacco is nicotine, of which there is 

 2% in Havana tobacco, 2-3% in Virginia, and in French 

 tobacco an average of 5%. The Frenchman consumes per year 

 about 1 kilogramme of tobacco, that is to say, he absorbs in that 

 time 50 grammes of nicotine. Fere ( x ) found that, in very small 

 doses, tobacco stimulates the muscular power ; it helps the associ- 

 tion of the ideas according to Claparede.( 2 ) But some careful 

 observations made by Weley ( 3 ) have established that nicotine, 

 in a solution of its tartaric salt, produces a typical effect on the 

 muscles, which consists of an initial diminution of their power, 

 and then an increase followed by a gradual fall. Altogether, 

 there is a reduction in the contractability of the muscles, the 

 increase of power being quite temporary. 



The smoke of tobacco, writing paper, straw, and wood all 

 contain carbon dioxide ( 4 ) and "furfurol."( 5 ) 



186. The Influence of Dust. The atmosphere, especially in 

 industrial towns, is always vitiated by dust and smoke, which 

 remain in suspension owing to the moisture in the air and form a 

 veritable fog. In gas works and foundries the air may contain 

 grains of coal, iron, oxide of lime, silica, etc. 



Some smoke is corrosive, because it contains hydrochloric, 

 hydrofluoric, or sulphuric gases ; in other cases it is sharp and 

 penetrating, thus facilitating the ingress of microbes into the 

 organism ; and some are pathogeonus, causing, for instance, 

 anthracosis, the pneumoconiosis of miners, silicosis of the lungs, 

 the illness of mill stone cutters, etc. 



In Paris, these industrial fogs are sometimes 400 to 600 metres 

 thick. They come from the north-east district, where the 

 factories are, blown by a gentle wind (velocity 2 to 3 metres), 

 over Paris. They disperse with a stronger wind (4 to 5 metres), 

 which blows from west south-west. The lowering of the baro- 

 metric pressure, the humidity and the temperature increases these 

 fogs.C) 



Dry dust is easily combustible when held in suspension in the 

 air. One must distinguish ( 7 ) between oil dusts, containing less 



Fe"re (Arch, de Neurologic, 1901, p. 463). 



" 



f 



1911). 



( 6 ) Furfurol is a toxic aldehyde C 5 H 4 O 2 ; methyl alcohol and wood vinegar 

 contain some of it. 



( 6 ) Jaubert (Revue Gin. Sc., 1910, p. 842). 



( 7 ) Experiments made at Frameries, Lievin, Altofts (Yorkshire), Glesen- 

 kircken (Germany), Rossitz (Austria), and at Berlin sugar works and 

 distilleries. (Rev. G&n. Sciences, 1911, p. 477). 



