MEASURING THE USEFULNESS OF FEEDS 



39 



The respiration apparatus. — This is an air-tight chamber, ar- 

 ranged with such devices that all that enters and comes from the body 

 of the animal placed within it can be accurately measured and studied. 

 In some cases mechanical work is performed, while in others the 

 animal is at rest. Everything which passes into the animal — air, food, 

 and water — is carefully measured and analyzed so that the exact in- 

 take of the body is known. The air is in turn drawn from the cham- 



Fig. 13.- — The Eespiration Calorimeter at the Pennsylvania 



Station 



Calorimeter chamber jn the corner of the room at the left. Thru the use of 

 this apparatus much light has been thrown on the value of different classes of 

 feeds for farm animals. (From Armsby, Pennsylvania Station.) 



ber and analyzed, and the feces and urine passed by the animal are 

 likewise weighed and analyzed. If the intake is larger than the outgo, 

 the animal has increased in body substance ; if less, it has lost. For 

 example, if the feed given a steer during 24 hours contains 0.75 lb. of 

 nitrogen and the feces and urine voided during the same day contain 

 0.64 lb., the steer has stored 0.11 lb. of nitrogen in its body during the 

 day in the form of protein tissue. Similarly, if the feed contains 



