260 



VETERINARY PHYSIOLOGY 



(2.) The excretion of matter. This is determined by 

 analysing the air entering and the air leaving the chamber, 

 and thus finding the amount of CO2 and HgO given off, and 

 by analysing the other excretions for nitrogen and carbon. 

 Methane and hydrogen excreted accumulate in the chamber 

 and connected parts. The amount is determined by analysis 

 at the end of the experiment. 



(3.) The amount of O2 absorbed. 



(4.) The composition and energy value of the food. 



By this means an accurate measurement can be made of the 



■rT T-'-rrfT".if/iir/n. 



Fig. 134. — The Chamber of the Respiratory Calorimeter. E is the double- 

 doored opening fur the supply of food and removal of the excreta. 



intake of matter and energy in the food and the output of 

 matter and energy from the body, and thus the relationship 

 between them can be determined. 



When man is used as the experimental animal the 

 chamber is provided with a folding-bed, writing-table and 

 chair, and an ergometer consisting of a fixed bicycle working 

 against a known resistance. The energy expended on the 

 work done on the bicycle can thus be measured in addition 

 to the enel-gy expended as heat. This apparatus has been 

 largely used to determine the energy and material exchange 

 in work in man. 



(2.) Indirect Calorimetry. — By this method an estimate is 

 made of the 0^ consumed and of the CO2 given off, and 

 from this, conclusions may be drawn, as already indicated, 

 as to the amounts of the proximate principles consumed, 

 and of the energy liberated. The amount of proteins used 

 may be determined by estimating the excretion of nitrogen, 



