42 The Ottawa Naturalist [June 



see how the bacilli of tuberculosis reach the tissues. We thus 

 see that it is in the foul, deoxidized air of tenements that we are 

 to look for congested, catarrhal mucous membranes, and for 

 infection reaching the mouth, through nasal catarrh making 

 mouth-breathing inevitable. We thus have the double evils 

 of imperfect nutrition from insufficient oxygen, and of the 

 poisonous effects of infected air. These slum conditions, hov/ever 

 bad they may be in southern cities, are relieved by the outdoor 

 life possible even in winter, while in northern cities we have the 

 impure air of houses with the abnormal dryness of furnace- 

 heated houses, due to the great differences in temperature and 

 moisture between indoor and outdoor air in the winter months. 

 When it is realized, for instance, that in Ireland, with its small 

 chilly cabins, heated only with turf fires, the deaths from diph- 

 theria in 1893 were but 0.08 per 1,000, and in London 0.78, and 

 that while the death-rate in all Scotland in 1892 was 2.3 per 

 1,000, that in the rural fishing villages with their cold and wet, 

 was 1.7 per 1,000, it will be seen that the con- 

 ditions of house atmospheres are the most potent influences 

 of any single factor in climate. To give but a single Canadian 

 example: I have found that in the beautiful foot-hill climate 

 of our own Alberta, the death rate of some of the Indians on 

 certain reservations, where they live in small, crowded and 

 insanitary houses, reached last year as high as 80 per 1,000, 

 largely due to consumption. 



Manifestly then, the maintenance of cleanliness in houses, 

 together with an abundance of warm air with sufficient moisture, 

 is primarily of all conditions that upon which health in temperate 

 climates depends. 



Carbonic Acid It has been already explained how oxygen obtains 

 entrance to the tissues, and to what extent. In the tissues it is taken 

 up by the red corpuscles through the thin lining membrane of the 

 lungs, and by them carried to the tissues where it unites with 

 their carbon to form carbonic acid. Some 1,400 grains, or 2 

 pounds of carbonic acid is given off by the lungs in twenty-four 

 hours. Thus we see that oxvgen burns up the wastes of the body 

 to the extent of nearly 3 pounds givenoff daily, further increased 

 one-third by active exercise. It need hardly be pointed out 

 that this active life process produces heat, and that it goes on 

 best and normally in the pure outdoor air, which on the plains 

 and mountains is almost germ-free. If then, wastes are pro- 

 duced by this organic combustion and are thrown off by the 

 lungs, skin and kidneys, it is apparent that the fuel thus burnt 

 up demands that a fresh supply, in other words, food, be taken 

 Jito the system. So we see how absolutelv essential it is if we 



