l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 63 



toxicity of the expired air. Billings, Mitchell, and Bergey say, in 

 the monograph referred to, that the injurious effects of such air ob- 

 served appeared to be due entirely to the diminution of oxygen, or 

 the increase of carbonic acid, or to a combination of these two fac- 

 tors. They consider that the principal, though not the only, causes 

 of discomfort to people in crowded rooms are excessive temperature 

 and unpleasant odors. 



We shall see, further on, that later studies show that the relative 

 proportions of oxygen and carbonic acid are not per se such impor- 

 tant factors. 



Dr. Milton J. Rosenau, professor of preventive medicine and 

 hygiene in Harvard Medical School, said in his recent address^ on 

 " Ether Day " at the Massachusetts General Hospital : 



One of the fallacies that has fallen is the relation of the air to the spread of 

 infection. The virus of most communicable diseases was believed to be in 

 the expired breath, or exhaled as emanations of some sort from the body. 

 These emanations were said to be carried long distances — miles — on the wind. 

 The easiest, and therefore the most natural way, to account for the spread 

 of epidemic diseases was to consider them as air-borne. Nowadays the sani- 

 tarian pays little heed to infection in the air except in droplet infection, and 

 the radius of danger in the fine spray from the mouth and nose in coughing, 

 sneezing and talking is limited to a few feet or yards at most. The more 

 the air is studied the more it is acquitted as a vehicle for the spread of the 

 communicable diseases. 



It was a great surprise when bacteriologists demonstrated that the expired 

 breath ordinarily contains no bacteria. Most micro-organisms, even if wafted 

 into the air soon die on account of the dryness, and especially if exposed to 

 sunshine. The relation of the air to infection is nowhere better illustrated 

 than in the practice of surgery. At first Lister and his followers attempted 

 to disinfect the air in contact with the wound by carbolic sprays. Now the 

 surgeon pays no heed to the air of a clean operating room, but ties a piece 

 of gauze over his mouth and nose, and also over his hair, to prevent infective 

 agents from falling into the wound from these sources. 



How complicated this entire subject is we can readily see from the 

 review ' made by Dr. Henry Sewall, of Denver, of recent experimen- 

 tal studies by Zuntz, Haldane, Rosenau and Amoss, Heymann, Paul, 

 Ercklentz and Fliigge, Leonard Hill and others. This review de- 

 serves to be read carefully. It sums up our latest knowledge and 

 leads to some surprising conclusions. After describing the Black 

 Hole of Calcutta, in which one hundred and forty-six Europeans 



^ Boston Medical and Surgical Journal, November 6, 1913. 



" On What do the Hygiene and Therapeutic Virtues of the Open Air De- 

 pend? by Henry Sewall, Ph. D., M. D. (Journ. Amer. Med. Ass., Jan. 20, 

 1912). 



