336 



PRACTICAL PHYSIOLOGY 



expired air to contain 3*54 per cent. CO 2 and 16-86 per cent. O 2 , that the 

 inspired air contained 0-03 per cent. CO 2 and 20-93 per cent, oxygen, 

 and that the total volume of air expired was 99-75 litres. The corrected 

 volume was 90-96 litres. Then the amount of carbon dioxide expired 

 was at and 760 mm. 



3.54-0-03 

 100 



x 90-96 = 3-192 litres. 



In order to obtain the true amount of oxygen taken in, the " apparent 

 respiratory quotient is first obtained. 



3-54-0-03 

 20-93-16-86 



0-862. 



This is not the true respiratory quotient as the volume of nitrogen 

 present has altered in relation to the oxygen. Haldane has devised 

 the following table which gives the true R.Q. from the apparent : 



The apparent respiratory quotient 0-86 is then from this table 0-83. 

 If the volume of carbon dioxide given off is divided by this figure, the 

 true respiratory quotient, the volume of oxygen absorbed is obtained. 

 In the example given then 3-192 -^ 0-83 = 3-840 litres of oxygen. 

 As the duration of the experiment was ten minutes it follows that the 

 oxygen consumption was at the rate of 384 c.c. per minute. 



The relative combustion of carbohydrate and fat can be calculated 

 from the respiratory quotient as, the experiments being of short duration, 

 it is assumed that during the actual period of the experiment only 

 carbohydrate and fat are utilised. If the nature of the experiment 

 demand it, the protein consumption can be determined from the output 

 of nitrogen in the urine. For every gramme of urinary nitrogen 8-45 

 gm. oxygen (1 gm. O 2 = 0-699 litre) are required for the oxidation 

 processes and 9-35 gms. of carbon dioxide (1 gm. CO 2 = 0-5087 

 litre) are given off. If then the appropriate amounts of oxygen and 

 carbon dioxide be deducted from the total amount of oxygen taken in 

 and of carbon dioxide exhaled a non-protein R.Q. is thus obtained and 

 from this an accurate estimate of the material utilised in a given time 

 can be made. 



The fact must, however, never be forgotten that the R.Q. is a ratio 

 and nothing more, and moreover it is a ratio of many components. 



Not only can the relative combustions be determined but a 

 caloric value for each litre of oxygen taken in has been worked out. 

 The following table from Zuntz and Loewy summarises these 

 results : 





