194 RESPIRATION 



gas-burner liberates five cubic feet in the same time, therefore 

 spoiling about as much air as ten men. A fire burning in a 

 grate or stove emits some impure gases, and at the same time 

 abstracts from the air as much oxygen as twelve men would 

 consume in the same period, thus increasing the relative 

 amount of carbonic acid gas in the air. From furnaces, as 

 ordinarily constructed, this and other gases are constantly 

 leaking and poisoning the air of tightly-closed apartments. 



34. Effects of Impure Air. Carbonic acid gas, in its pure 

 form, is irrespirable, causing rapid death by suffocation. Air 

 containing forty parts per thousand of this gas (the composition 

 of the expired breath) extinguishes a lighted candle, and is 

 fatal to birds ; when containing one hundred parts, it no longer 

 yields oxygen to man and other warm-blooded animals, and is, 

 of course, speedily fatal to them. In smaller quantities, this 

 gas causes headache, labored respiration, palpitation, uncon- 

 sciousness, and convulsions. 



35. In crowded and badly ventilated apartments, the air is 

 breathed over until it contains from six to ten times the natural 

 amount of carbonic acid gas. This contaminated air causes 

 dullness, drowsiness, and faintness, because the dark, impure 

 blood circulates through the brain, oppressing that organ, and 

 causing it to act like a blunted tool. This is a condition not 

 uncommon in our schools, churches, and court-rooms the 

 places of all others where it is desirable that the mind should 

 be alert and free to act; but, unhappily, an unseen physio- 

 logical cause is at work, dispensing weariness and stupor over 

 pupils, audience, and juries. (Read Notes 7 and 8.) 



7. The Ground-Atmosphere and its Relations to Dwellings. "The 

 soil, which naturally contains wholesome air, and gives facility to its every 

 movement, is not less permeable by poisonous gases, which are often found 

 to pervade and issue from it. It is easy to find illustrations of the fact 

 that people are poisoned through the ground, since it is almost a daily 

 occurrence. Here is one, related by an eminent authority, von Petten- 

 kofer: 'In a residence at Augsburg, apparently endowed with every 

 qualification for health and comfort, several priests lived together. On a 



84. Effects of inhaling carbonic acid alone ? In small quantities ? 



85. Effects of the air in crowded and badly-ventilated rooms ? 



