NO. 23 INFLUENCE OF ATMOSPHERE ON HEALTH 93 



schools, theaters, and barracks, are such that they can have no 

 effect upon the incidence of respiratory disease and the higher death 

 rate which statistical evidence has shown to exist among persons 

 living in crowded and unventilated rooms. The conditions of 

 temperature, moisture, and windless atmosphere in such places 

 primarily diminish the heat loss, and secondarily the activity of the 

 occupants, as also the total volume of air breathed, oxygen taken in, 

 and food eaten. The whole metabolism of the body is thus run at 

 a lower plane, and the nervous system and tone of the body are 

 unstimulated by the monotonous, warm, and motionless air. At the 

 same time, the number of pathogenic organisms is increased in such 

 localities, and the two conditions run together, — diminished immunity 

 and increased mass influence of infecting bacteria. 



The volume of blood passing through, and of water vapor 

 evaporated from, the respiratory mucous membrane must have a great 

 influence on the mechanisms which protect this tract from bacterial 

 infection. Mr. F. F. Muecke * and one of us (L. H.) have found that 

 convected heat, from steam coils, closed stoves, etc., swells the mucous 

 membrane of the nose and air sinuses, and obstructs the air-way. On 

 the other hand, radiant heat, from an open fire or gas fire, causes the 

 skin to sweat and does not affect the nasal mucous membrane. The 

 swelling of the nose favors massive local infection. 



We conclude that rooms should be heated by radiant heat and ven- 

 tilated with cool outside air, and the conditions of a spring day — sun- 

 light and cool breeze — approximated to as nearly as possible. The 

 heated air of rooms is the factor which favors infection and the 

 spread of coryza, influenza, phthisis, etc. 



In the warm, moist atmosphere of a crowded place, the infection 

 from spray, sneezed, coughed, or spoken out, is great. On passing 

 from such an atmosphere out into the cold, moist external air the 

 respiratory mucous membrane is suddenly chilled, the blood-vessels 

 are constricted, and the defensive mechanism of cilia and leucocytes 

 is checked. Hence the prevalence of colds in the winter. In the 

 summer the infection is far less, and the sudden transition from a 

 warm to a cold atmosphere does not occur. We believe that infec- 

 tion is largely determined, (i) by the mass influence of the infecting 

 agent ; (2) by the swelling of the mucous membrane of the nose, and 

 (3) by the sudden transition from warm to cold surroundings, which 

 checks the immunizing mechanisms. Colds are not caught by expos- 



1 Lancet, May 10, 1913, p. 1291. 



