RESPIRATORY INTERCHANGE UNDER DIFFERENT CONDITIONS 527 



low. Toward larger amounts of CO2, the system very readily reacts 

 by a greater respiratory rate and amplitude and other changes. Thus, 

 if it is said that the air of a room, in which more than 0.07 volume 

 per cent, of CO2 is present, feels distinctly close and uncomfortable. 

 This sensation should not be referred to a deficiency of O nor to a super- 

 fluity of CO2, but rather to its temperature, its humidity, and its con- 

 tent in volatile odorous substances and dust. 



In poorly ventilated rooms the CO2 may reach 0.30 volume per 

 cent., and in crowded lecture halls 0.80 volume per cent., but the dis- 

 comfort experienced in places of this kind may be lessened consider- 

 ably either by lowering the temperature and the humidity of the air or 

 by fanning it. Even in rooms in which the CO2 content is 1.0 or 2.0 

 per cent., no discomforts are experienced so long as the aqueous vapor 

 and the temperature are kept low, but these facts are not cited to 

 minimize the importance of the composition of the air, but solely to 

 show that the other two factors play an important part. In a general 

 way, it may be stated that optimum conditions prevail when the tem- 

 perature of the room is between 65° and 68° C, and when the moisture 

 equals 50 to 75 per cent, relative humidity. The air itself should not 

 contain more than 0.06 per cent, of CO2 and should be as free as pos- 

 sible from bacteria, gaseous admixtures and dust. If it contains 

 more than this amount, artificial means should be resorted to to renew 

 it with a frequency which is to be determined by calculation from the 

 proportion of CO2 per volume of air. 



It seems, therefore, that the injurious consequences of living in 

 poorly ventilated quarters are caused, at least to some extent, by the 

 physical qualities of the respired air, but precisely in what respect a 

 hot and humid atmosphere proves harmful, has not been fully deter- 

 mined. Hermanns 1 has found that the temperature of persons living 

 in very restricted quarters, rises considerably, and furthermore, the 

 results of the New York State Commission on Ventilation^ indicate 

 that a high temperature and high humidity give rise to an elevation 

 of the systolic and diastolic pressures, as well as to a diminution of the ' 

 vascular tonus and a lowering of the resistance of the body against 

 bacterial infections. The general disinclination to exercise experienced 

 at this time, seems to have a deeply seated cause, because the muscles 

 themselves are incapable of performing a normal amount of work. 

 Lee and Scott^ have shown, that a loss of blood sugar results at this 

 time which under extreme conditions may equal 5 per cent, of normal. 



1 Archiv fiir Hygiene, i, 1883, 1. 



2 Lee, Science, N. S., xliv, 1916, 183. 

 s Am. Jour, of Physiol., xl, 1916, 486. 



