20 METABOLISM DURING WALKING. 



UNIVERSAL RESPIRATION APPARATUS. 



The universal respiration apparatus in its various adaptations has 

 been frequently described in the publications from this Laboratory. 1 

 Briefly stated, it consists of a closed ventilating air-circuit, with pro- 

 visions for a moderate degree of expansion in the air-volume and con- 

 nection with the subject by means of a mouthpiece or nosepiece. The 

 air is kept in motion by a rotating ventilator or blower, actuated by an 

 electric motor, which forces the expired air through absorbents for 

 moisture and carbon dioxide arid returns it to the subject for rebrejath- 

 ing afte!r the air has been moistened and the oxygen dejficit has been 

 made up from an oxygen-supply connected with the system and 

 metered. Sulphuric acid is used for the water-absorbent and moist 

 soda-lime for the carbon-dioxide absorbent. The combined increase in 

 the weight of the soda-lime containers and the supplementary water- 

 absorbqr gives data fojr calculating the volume of carbon dioxide 

 expired by the subject. The amount of oxyge^i consumed is deter- 

 mined from the readings of a calibrated integrating meter connected 

 with the oxygen-supply. The absorbing system, mounted on a two- 

 shelved table, is in duplicate, with suitable valve connections which 

 permit the use of either series of absorbers at will. 



Since the amount of work to be performed was greater than in the 

 study made by Benedict and Murschhauser, the ventilating system was 

 equipped with a larger motor and driving-pulley. The speed of the 

 one-sixth horse-power electric motor employed was controlled by a 

 rheostat, fixed upon the front of the table, which permitted the varia- 

 tion of the ventilating air-current between 65 and 100 liters per minute. 

 The two sulphuric-acid containers, or "Williams bottles," which were 

 inserted in the system next to the blower, each had a capacity of 2.5 

 liters and were followed by a train of two large soda-lime containers 

 for the absorption of the carbon dioxide, and a third large Williams 

 bottle or air-drier for absorbing any moisture carried over from the 

 moist soda-lime. 



Moistener. The dry air, after it left the carbon-dioxide absorbers, 

 was moistened by passing it through water contained in a large Williams 

 bottle. None of the subjects complained that the air was too dry. A 

 test was made of the percentage of humidity by inserting a psychro- 

 meter in the air-circuit, and an average figure of 70 per cent was found 

 when the rate of ventilation was highest. This figure has been used 

 in reducing the volume of the pulmonary ventilation to standard 

 conditions. 



Spirometer. In the research of Benedict and Murschhauser, a 

 rubber bathing-cap was used as a tension equalizer for fluctuations 



Benedict, Deutsch. Archiv f. klin. Med., 1912, 107, p. 156; Benedict and Cathcart, Carnegie 

 Inst. Wash. Pub. No. 187, 1913, p. 27; Benedict and Murschhauser, Carnegie Inst. Wash. Pub. 

 No. 231, 1915, p. 31; Carpenter, Carnegie Inst. Wash. Pub. No. 216, 1915, p. 21. 



