THE COMPOSITION OF EXPIRED AIR. 409 



immunity produced by it had been previously noted. The experiments 

 show that such an immunity may either exist normally or be produced 

 in certain mice, but that these cases are very exceptional, and it is very 

 desirable that a special research should be made to determine, if pos- 

 sible, the conditions upon which such a continuance of immunity 

 depends. 



8. An excessively high or low temperature has a decided effect upon 

 the production of asphyxia by diminution of oxygen and increase of 

 carbonic acid. At high temperatures the respiratory centers are 

 affected, where evaporation from the skin and mucous surfaces is 

 checked by the air being saturated with moisture; at low temperatures 

 the consumption of oxygen increases, and the demand for it becomes 

 more urgent. 



So far as the acute effects of excessively foul air at high temperatures 

 are concerned, such, for example, as appeared in the Black Hole at 

 Calcutta, it is probable that they are due to substantially the same 

 causes in man as in animals. 



9. The proportion of increase of carbonic acid and of diminution of 

 oxygen, which has been found to exist in badly ventilated churches, 

 schools, theaters, or barracks, is not sufficiently great to satisfactorily 

 account for the great discomfort which such conditions produce in many 

 persons, and there is no evidence to show that such an amount of 

 change in the normal proportion of these gases has any influence upon 

 the increase of disease and death rates which statistical evidence has 

 shown to exist among persons living in crowded and unventilated 

 rooms. The report of the commissioners appointed to inquire into the 

 regulations affecting the sanitary conditions of the British army (1) 

 properly lays great stress on .the fact that in civilians at soldiers' ages, 

 in twenty-four large towns, the death rate per 1,000 was 11.9, while in 

 the foot guards it was 20.4 and in the infantry of the line 17.9, and 

 showed that this difference was mainly due to diseases of the lungs 

 occurring in soldiers in crowded and unventilated barracks. These 

 observations have since been repeatedly confirmed by statistics derived 

 from other armies, from prisons, and from the death rates of persons 

 engaged in different occupations, and in all cases tubercular disease of 

 the lungs and pneumonia are the diseases which are most prevalent 

 among persons living and working in unventilated rooms, unless such 

 persons are of the Jewish race. But consumption and pneumonia are 

 caused by specific bacteria, which, for the most part, gain access to 

 the air passages by adhering to particles of dust which are inhaled, 

 and it is probable that the greater liability to these diseases of persons 

 living in crowded and unventilated rooms is to a large extent due to 

 the special liability of such rooms to become infected with the germs 

 of these diseases. It is, however, by no means demonstrated as yet 

 that the only deleterious effect which the air of crowded barracks or 

 tenement-house rooms, or of foul courts and narrow streets, exerts upon 



