RESPIRATION. 547 



When the percentage of in the inspired air falls so low as to cause marked 

 dyspnoea, the respiratory quotient rapidly rises. This is owing on the one 

 hand to the diminished quantity of O absorbed, and on the other hand to the 

 increased production of CO 2 as a consequence of excessive activity of the 

 muscles of respiration. Speck (p. 543) found that when the proportion of O 

 was very low the quotient rose as high as 2.258. 



E. PRINCIPLES OF VENTILATION. 



Breathing within a confined space, as in a small unventilated room or in a 

 large room in which a considerable number of persons are assembled, causes 

 a gradual diminution in the quantity of O and an accumulation of CO 2 , moist- 

 ure, and organic matter. In regard to O, even in the worst ventilated rooms 

 the atmosphere seldom contains as little as 1 5 volumes per cent., which is suffi- 

 cient to permit of undisturbed respiration. When the proportion of CO 2 

 exceeds 0.07 volume per cent, the air becomes disagreeable, close, and stuffy 

 offensive characters which are due neither to the increase of CO 2 nor to a 

 deficiency of O, but to the presence of organic matter termed " crowd-poison." 

 Air from which this organic exhalation is absent may contain considerably 

 more CO 2 without causing any unpleasant effects. In well- ventilated rooms 

 the proportion of CO 2 does not exceed 0.05 to 0.07 volume per cent. ; in 

 badly- ventilated rooms it may reach 0.25 to 0.30 volume per cent. ; while 

 when a large number of tndividuals are crowded together, as in lecture- 

 rooms, it may be as high as 0.70 to 0.80 volume per cent. This vitiation is 

 further increased by the burning of gas or oil, 150 liters of ordinary coal-gas 

 (enough to supply a large burner for about an hour) consuming all the O in 

 1200 liters of air, or as much O as is required by the average individual 

 in eight hours, besides loading the air with various deleterious products of 

 combustion. 



While the accumulation of CO 2 even in the worst ventilated rooms is not 

 in itself pernicious, its percentage is a practical working index of the amount 

 of organic matter present, and therefore of the degree of vitiation. It has 

 long been recognized that the atmosphere of crowded, badly-ventilated rooms 

 is poisonous, but the precise nature of the toxic element is unknown. Brown- 

 Sequard and d'Arsonval condensed the moisture of the expired air and found 

 that from 20 to 40 cubic centimeters would kill a guinea-pig ; but their results 

 have been contradicted positively by Dastre and Loye, Lehmann, Geyer, and 

 others. The poison in expired air, whatever it may be, is of an impalpable 

 nature, and is neither dissolved nor condensed in the moisture exhaled. 



The quantity of fresh air required during a given period depends upon the 

 size of the individual, the degree of activity, and the size of the air-space. 

 Assuming that an individual eliminates 900 grams, or 458 liters, of CO 2 per 

 diem, and that the percentage of CO 2 is to be kept at a standard not exceeding 

 0.07 volume per cent., 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 



