TECHNIQUE FOR METABOLISM DURING REST. 



109 



this covered pan air was continuously withdrawn through a series of 

 U -tubes at such a rate that by the time the next sample was ready to 

 be delivered into the pan the first sample had been practically all with- 

 drawn.^ By this method, however, air was but intermittently dis- 



yMf^)^/)//// ^^^ 



Fig. 13.— Details of device for regulating pressure inside of cylindrical cans above wind 



chest. 



A, wind chest; B, opening for delivery of major portion of air to outside; Ci, C2, cylindrical cans 

 above wind chest; 61, 62, openings for delivery of air from Ci, C% to outside; the weights of the 

 bathing caps on tops of cans Ci, Cj are counterpoised by the springs, si, si, the tensions of 

 which are regulated by the nuts, n\, 7Vi\ when the pressure inside of cans d, Ci gets too low, 

 the contact shown between disks di, 4 is closed, and the current passing through this circmt 

 draws down the telegraph sounder shown in fig. 11; this permits the opening of tube mi or m-i 

 (fig. 11) and by-passes a portion of the air, thus drawing less air from the can Ci or Ci. In 

 this way the amount of air drawn from Ci or C-i is regulated so that the air inside of either can 

 is practically always at atmospheric pressure, dz is a disk for preventing the bathing cap 

 from rising unduly. 



charged into the pan and with a pump that, while not capable of exert- 

 ing any great positive pressure, nevertheless could easily overcome the 

 slight friction of the counterpoise weight of the rubber diaphragm. 

 Our present problem, however, was to remove the air from the samp- 



> Atwater and Benedict, U. S. Dept. Agr., Office Expt. Sta. Bui. 109, 1902, p. 27. 



