.May, 1929] SIMPLIFIED TECHNIQUE FOR MEASURING ENERGY 13 



Appliance for Feeding and Watering 



In order to feed the aniniul during a respiration experiment it was neces- 

 sary to provide facilities to introduce a feed and to remove any feed re- 

 fused from a previous meal under conditions in which an accurate account 

 could be made for any changes in the composition of the chamber air 

 caused by this operation. This provision was obtained by a movable 

 feed box (Plate 1 and Figs. 3 and 4) which can be sUd out of the chamber 

 proper into a small, sheet-metal compartment soldered to the outside 

 front of the chamber wall. By means of a heavy, sheet -iron shutter which 

 can be raised and lowered from the outside, the opening connecting the 

 chamber with the small outside compartment may be closed practically 

 air-tight. The top of the outside compartment is provided A\ith a lid, 

 which sets in a water seal. Hence at feeding time the shutter is raised, 

 the feed box is moved to the outside compartment, and the shutter is 

 lowered again, closing off the respiration chamber. The lid is then re- 

 moved from the water seal and any left-over feed is taken out and weighed. 

 A fresh feed is then placed in the feed box, the hd is replaced in the water 

 seal, and the feed box is restored to the chamber by the same operation. 



The operation of moving the feed box from one compartment to the 

 other is accomphshed by means of a hand crank on the outside of the 

 apparatus, as is also the raising and lowering of the shutter b}' which the 

 two compartments may be closed off from each other. 



The feed box rides on four pieces of 2" x 4" material placed edgewise 

 and spaced five inches apart, and extending the entire distance to which 

 the feed box must move. Between the two middle pieces are two small 

 bicycle sprockets, one at each end, carrying a continuous chain. The 

 sprocket in the smaller outside compartment is mounted on a long shaft 

 which projects through a machined bearing to the outside where it is fitted 

 with a crank to move the chain backward, or forward. To facihtate 

 removal of the feed box for cleaning, the chain is not attached directly to 

 it but to a piece of sheet-iron, 5 inches wide and one-eighth inch in thick- 

 ness, which is bent up at the ends so that the feed box just fits into it. 

 This sheet-iron saddle is of just sufficient width to fit between the two 

 middle pieces of 2" x 4" on which the feed box rides. This plate is sup- 

 ported by two cleats which are nailed in to the 2" x 4" low enough to leave 

 the top surface of the plate flush with the top surface of the 2" x 4". 



The water tank is hung on the outside of the wooden framework (Plate 

 1) which encloses the feed box inside the respiration chamber. The w^ater 

 is introduced through a tube which enters the tank in the bottom so that 

 any water refused can be drawn off for reweighing. The tube is so ad- 

 justed as to maintain a constant water seal to prevent exchange of air. 



Ventilating Apparatus 



The original apparatus for ventilating the chamber, measuring the 

 volume of ventilation, and absorbing the carbon dioxide for weighing is 

 still in use. (See Plate 2, Fig. 5.) It consists of a small electric blower 

 located just outside the w^all of the chamber, which removes the air from 

 the chamber (See Fig. 5) and drives it into a large metal can, or wind- 

 chest, hung under the absorber table. Another electric blower, located on 

 the lower shelf of the table, removes an aliquot fraction of this air from the 



