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12 EFFECTS OF A VITIATED ATMOSPHERE 



many ways. It was recognized long ago that post-mortem wounds 

 are much more dangerous when received whilst fasting than during 

 the process of digestion, and it is possible that this may be due to 

 some extent to the increased number of leucocytes which occur in 

 the blood during the process. 



Exposure to a vitiated atmosphere, if of long duration, is a most 

 potent cause of the breaking down of immunity, and when con- 

 sidered on a large scale, and in view of its effect on the general 

 death and disease rate, is probably of greater importance than all 

 other causes combined. It is especially important in connection 

 with tuberculosis, and nothing is more striking than to notice its 

 effect on the peasantry of some regions, in which, in spite of 

 exposure to abundant fresh air during the daytime, and a supply 

 of food which certainly does not fall below the physiological 

 minimum, and is usually more abundant, phthisis and other 

 tuberculous diseases are rife. These affections are in general 

 common in cold and windy climates, and less prevalent in warmer 

 countries, and there is little doubt that the main reason for this is 

 the habit which dwellers in cold countries frequently contract of 

 hermetically sealing all entrances to their rooms to keep out the. 

 cold. But this is frequently seen in warmer regions, and even 

 throughout the South of England there is an almost universal 

 opinion amongst the lower classes that night air is injurious. 

 This is probably a survival from the time when malaria was 

 indigenous in this country. 



Apart from tubercle, the effect of bad air is especially mani- 

 fested in the causation of diseases of the lungs, nose, throat, etc., 

 and its effect is probably partly general and partly local. The 

 effect of irritating vapours is, of course, local. Thus exposure to 

 nitrous fumes is often followed by the rapid development of 

 pneumonia, and this is, or may be, due to the pneumococcus, 

 which is able to invade the injured lung. 



We do not know the mechanism by which ordinary vitiated air 

 acts on the general immunity. 



Prolonged anesthesia is probably a cause of considerable 

 importance, though one not easy to estimate. The prevalence of 

 ether-pneumonia is not yet ascertained, and has been hotly 

 debated. It falls, of course, into the same category as the 

 pneumonia due to irritating vapours, as described above. Apart 

 from this, however, there is reason to believe that prolonged 

 anaesthesia has some effect in lowering the general resisting 



