TECHNIQUE FOR METABOLISM DURING WORK. 123 



The cover, C, was prism-shaped, 134 cm. high and 79 cm. square on 

 its base, which fitted into the seal of the skirt. It was counterpoised 

 over pulleys on the ceiling and could be easily raised from the seal, 

 giving a clearance above the skirt of 66 cm. A circular plate glass 

 window, 0, 25 cm. in diameter, was inserted in the front of the cover. 



In addition to these main features there were the following accessory 

 parts : 



Air-drier (H) and psychrometer (G) ; tension equalizers {M and M') ; 

 resistance thermometers {N^ to N^); barometer; and gas-analysis appa- 



AIR-DRIER AND PSYCHROMETER. 



From the right side of the skirt near the front a 6 cm. pipe extended 

 along the side of the skirt to a drier (H) 40 cm. high and 30 cm. in diam- 

 eter, filled with 15 kg. of fused calcium chloride. The calcium chloride 

 was in small lumps about 1 cm. in diameter, which allowed a free 

 passage of the circulating air. It was fairly efficient in absorbing 

 power, and kept the humidity within the chamber at a point vary- 

 ing from 20 to 50 per cent. The psychrometer, G, was inserted at 

 the point where the 6 cm. pipe left the skirt. 



From the drier a 10 cm. pipe, J, carried the dry air back to the cham- 

 ber which it entered at the rear of the skirt. This return pipe had a 

 total length of 250 cm. and the mill was so located in the room that 100 

 cm. of this pipe passed through and extended horizontally along the 

 face of the doorway, I, of an adjoining room. In this part of the cir- 

 cuit were inserted the stopcocks through which air samples could be 

 simultaneously withdrawn. The doorway was closed up so as to pro- 

 vide a room of reasonably constant temperature for the gas analysis. 

 The last section of this return pipe, L, was made removable by means of 

 two small water seals, K and K', so that, when this section was hfted 

 from its connection with the chamber, the large cover could be lowered 

 into or raised from the skirt without altering the tension of the air 

 inside the chamber. 



VENTILATION OF CHAMBER. 



A "Sirocco" blower, F, within the chamber, attached to the circu- 

 lating air pipe at the point where it left the skirt, maintained an air- 

 current through the system of 1,000 liters a minute. An electric fan, 

 E', was placed in the top of the cover in such a position as to send a cur- 

 rent of air over the head and shoulders of the subject, while a similar 

 fan, E, was placed under the belt between the two pulleys of the tread- 

 mill. These two fans, E and E\ together with the circulating air- 

 blower, F, previously referred to, were relied upon to keep the air well 

 mixed within the chamber during the active periods of walking. In 

 addition to these a large 15 cm. blower, capable of dehvering 12 cubic 

 meters of air a minute, was mounted outside on a table which could be 

 rolled up to the side of the skirt. During the intervals between the 



