100 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



OUTGOING AIR. 



From the experience of more than a decade with the ventilation of 

 various types of respiration chambers, it was clear that a provision for 

 the rapid renewal of air inside the chamber was unnecessary. Experi- 

 ments at Wesleyan University for periods of 2 to 13 days have shown 

 that if the ventilation is sufficient to maintain the carbon-dioxide 

 content of the air inside the chamber at not more than from 0.5 to 

 1 per cent, no discomfort is experienced by human subjects. Indeed, 

 in one instance a human subject Uved in an atmosphere containing 

 approximately 2 per cent of carbon dioxide for more than 24 hours 

 without discomfort. Without doubt the greatest factors in determin- 

 ing so-called "bad" air are temperature and humidity; we firmly be- 

 lieve that carbon dioxide, per se, has no influence. 



Until the oxygen content is lowered to considerably below 15 per 

 cent there is no evidence of labored respiration or indication of oxygen- 

 want. On the other hand, since moisture in the air and especially a 

 high temperature are extremely disagreeable, it became necessary to 

 remove the moisture by a sufficient flow of air in the chamber or to 

 condense it by use of brine, which likewise provided for temperature 

 control. Finally, we decided that the safest procedure would be to 

 adjust the rate of ventilation so that the percentage of carbon dioxide 

 residual in the air in the chamber would be not far from 0.5 per cent, 

 and to control the total amount of the ventilating air-current so 

 that this adjustment could be made within wide limits. In other 

 words, when but a small amount of carbon dioxide is being produced, 

 the total ventilation would be low; when a large amount, it would be 

 very high. This fluctuation in the possible ventilating capacity of 

 the chamber was readily secured by the use of the rotary air-impeller, 

 referred to in a foregoing paragraph. These impellers, the discharge 

 of which may be cut down at will by butterfly valves, permit the move- 

 ment of a very large amount of air through the chamber in a very 

 short time. Indeed, with the impeller used here, with a discharge 

 of 97 mm. and with a speed of the armature shaft of 1,700 revolu- 

 tions per minute, it has been computed that the entire volume of the 

 chamber can be swept out in a very few minutes with full and free 

 discharge of the blowers. On the other hand, by reducing the delivery 

 by butterfly valves or other suitable device, the total ventilation of 

 the chamber can be brought to as small a volume as desired. 



It is thus apparent that the carbon-dioxide content of the outcoming 

 air will, under all circumstances, be very considerably greater than that 

 of normal air; hence the problem of measuring exactly the total carbon 

 dioxide removed from the chamber assumes grave importance. To 

 pass the entire air-current through soda-lime would, for reasons out- 

 lined previously, be wholly impracticable, as it would require an 

 absorption system of purifiers which would be diflGicult to maintain, a 



