440 AN AMERICAN TEXT-HOOK OF PHYSIOLOGY. 



0.07 volume percent., there would be required at least 1,440,000 liters of 

 fresh air during twenty-four hours, or about 60,000 liters (2000 cubic feet) per 

 hour. All circumstances, such as muscular activity, which increase the output 

 of C0 2 augment the demand for fresh air. When confined in rooms, every 

 person should have an air-space equal to about 28,000 liters, or 1000 cubic 

 feet, the floor-space should not be less than ^ of the cubic capacity of the 

 room, and the air should be renewed as often as twice an hour. In lecture- 

 rooms, school-rooms, etc. the air-space per individual is usually very small, so 

 that the renewal must be more frequent and in proportion to the limitation of 

 space per individual. 



Ventilation i> accomplished by natural and artificial means. The forces of 

 the wind, the differences in temperature within and without the building, the 

 natural diffusion of gases owing to variations in composition, etc., all cause 

 more or less circulation. Artificial ventilation is effected by the use of proper 

 appliances for the forced introduction of air into and expulsion from apartments. 



F. The Effects of the Respiration of Various Gases. 



The respiration of pure () takes place without disturbance of the respira- 

 tory processes. Lorrain Smith 1 has shown that O at the tension of the 

 atmosphere stimulates the Lung-cells to active absorption, at a higher tension 

 acts as an irritant, or pathological stimulant, and produces inflammation. 

 Dyspnoea is developed when the inspired air contains less than 13 volumes 

 per cent. (p. 435). Respiration of pure CO a (p. 436) is fatal within two 

 or three minutes, but an atmosphere containing as much as 25 to 30 per 

 cent, may be respired for a few minutes without ill effect (p. 436). Nitrogen, 

 hydrogen, and carburetted hydrogen (CH 4 ) may be inhaled with impunity if 

 they contain not less than 13 volumes per cent, of O. The respiration of 

 nitrous oxide or of air containing much ozone rapidly produces aiuesthesia, 

 unconsciousness, and death. Carbon monoxide (CO) and cyanogen are decid- 

 edly toxic, combining with haemoglobin and displacing oxygen. Sulphuretted 

 hydrogen, phosphoretted hydrogen, arseniuretted hydrogen, and antimoniu- 

 retted hydrogen are all poisonous and are all destructive to haemoglobin. An 

 atmosphere containing 0.4 volume per cent, of sulphuretted hydrogen is said 

 to be toxic Air containing 2 volumes per cent, of CO (carbon monoxide) is 

 quickly fatal. Certain gases and vapors — as, for instance, ammonia, chlorine, 

 bromine, ozone, etc. — produce serious irritation of the respiratory passages, and 

 may in this way cause death. 



G. Effects of the Gaseous Composition of the Blood on the 

 Respiratory Movements. 



Certain terms are employed to express peculiarities in the respiratory phe- 

 nomena: Ewpnoea is normal, quiet, and easy breathing. J yy/ma is a suspen- 

 sion of the respiratory movements. Hyperpnoea is a condition of increased 

 1 Journal of Physiology, 1899, vol. 24, |>. 19. 



