MUSCLE 



259 



bastion of fats and carbohydrates. When this is expressed 

 as a respiratory quotient, the amount of fats and carbo- 

 hydrates respectively used can be determined. 



Tables giving the significance of different respiratory 

 quotients are prepared and are used in such investigations. 



The following gives a rough indication of such a table. 



R.Q. Carbohydrates. Fats 



rOO 100 per cent. per cent. 



0-90 66 „ 34 



0-80 32 „ 68 



0-70 „ TOO 



Owing to the fact that the amount of protein decomposed 

 during the relatively short period of the collection of the 

 sample of expired air is, as a rule, trivial, the calculation 

 may be based solely on the combustion of carbohydrates 

 and fats. 



Calorimetry. 

 To determine the extent of these exchanges two different 

 methods have been employed. 



(1.) Direct Calorimetry. — By this method the amount of 

 energy liberated as heat is directly measured by means of a 

 Respiratory Calorimeter. This consists of an air-tight double- 

 walled room, in which an animal may be kept for a day or 

 longer at a time. It is 

 provided (1) with an ar- 

 rangement by which air 

 is sujjplied and the amount 

 of air measured ; (2) with 

 an arrangement by which 

 the heating of the air 



BtSPlRATION OUMBCR 



" U.wi.) I — 1 



and the amount of water 

 vaporised maybe measured; 

 (3) with an air-tight double 

 window, through which the 

 animal can be observed. 

 With this chamber it is possible to measure — 



(1.) The heat given off. This is measured by the extent 

 to which water circulating in special coils is heated and 

 by the amount of water vaporised. 



Fig. 133. — Diagram of a Respiration 

 Chamber to show the method of 

 anah'sis of the expired air and 

 the renewal of the supply of 

 oxygen. 



