NO. I AIR AND TUBERCULOSIS HINSDALE 27 



These results do not really give us anything definite, as the com- 

 parative factor is absent. 



Fog usually collects in the lower portions of a city, especially in 

 depressed localities known as hollows, where it remains until dis- 

 persed by air currents. The well-known increase of mortality in 

 cities during the continued presence of heavy fog with these addi- 

 tional contaminations have been recorded and commented upon for 

 years. The heavy, suffocating, poisonous quality of sulphur dioxide 

 is well known and has been the subject of several investigations. In 

 general, it may be said that the chief symptoms of poisoning with 

 sulphurous acid are those of irritation of the mucous membranes. 

 Even in five parts in 10,000 it acts as an irritant, causing sneez- 

 ing, coughing and lacrymation, bronchial irritation and catarrh 

 (Cushny). It is also credited with causing pneumonia and Prof. 

 Schaefer notes its power to produce asthma.^ Undoubtedly it would 

 aggravate pulmonary and laryngeal tuberculosis and either delay 

 or prevent a cure under the conditions described. 



AMMONIA IN THE AIR 



This gas is constantly present in the atmosphere, but in very 

 minute quantities. Fifty years ago Boussingault and, later, Schloes- 

 ing made careful investigations of this impurity of the atmosphere 

 and devised ingenious methods of estimating" its amount in air and 

 rain water. It usually exists only in combination with carbonic 

 or nitric acid ; very little is free. Water absorbs it freely and it has 

 been estimated that in France the annual rainfall brings to the 

 earth in the form of nitrogen nearly 5 kilograms per acre. The 

 presence of ammonia indicates organic putrefaction. Its amount 

 does not usually exceed a very few parts per million. It is usually 

 perceptible, as we all know, in and about stables. 



As far as any relation to tuberculosis is concerned, ammoniacal air 

 has for us only a remote interest. At one time it was strongly advo- 

 cated as a cure for pulmonary consumption and perhaps some his- 

 toric details may be of interest here. 



Dr. Thomas Beddoes, of London, published in 1803, " Considera- 

 tions on a Modified Atmosphere in Consumption Cases," and 

 strongly advocated residence in a cow stable for such cases. One 

 of his patients was Mrs. Finch, a daughter of Dr. Joseph Priestley, 



^ This accords with the conclusions of W. C. White and Paul Shuey, loc. cit. 

 The relation of Sea Fog to Tuberculosis is considered in the next chapter, 

 page 52. 



