BESPIRA TION. I J I '. I 



When the percentage of O 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 CQ 2 as a consequence of excessive activity of the 

 muscles of respiration. Speck (p. 435) found that when the proportion of 

 was very low the quotient rose as high as 2.258. 



E. Principles op 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.,, moist- 

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

 the atmosphere seldom contains as little as 15 volumes per cent,, which is suffi- 

 cient to permit of undisturbed respiration. When the proportion of C0 2 

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

 offensive characters which are due neither to the increase of C0 2 nor to a 

 deficiency of O, but to the presence of odorous principles given off chiefly by 

 the body and clothing. Air from which this organic exhalation is absent 

 may contain considerably more C0 2 without causing any unpleasant effects. 

 In well-ventilated rooms the proportion of C0 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 individuals 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 120O liters of air, or as much () as is required 

 by the average individual in eight hours, besides loading the air with various 

 deleterious products of combustion. 



While the accumulation of C0 2 even in the worst ventilated rooms is not 

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

 of vitiation. It has long been recognized that the atmosphere of crowded, 

 badly-ventilated rooms gives rise to discomfort, and by sonic the expired air 

 has been erroneously asserted to be toxic. Tims Brown-S6quard and d'Ar- 

 sonval condensed the moisture of the expired air and found thai from 20 to 

 40 cubic centimeters would kill a guinea-pig; but their results have been 

 contradicted positively by Dastre" and Love. Lehmann, Geyer, and others. 

 The vitiation of the air of badly-ventilated rooms cannot be said to be due to 

 any particular poison, but to an accumulation of odorous principles arising 

 from uncleanly bodies, clothes, and surroundings, and also to an accumula- 

 tion of C0 2 , and to a deficiency of O in extreme instances. 



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 158 liters, of C0 2 per 

 diem, and that the percentage of C0 2 is to be kept at a standard not exceeding 



