ADVANCED CHEMICAL PHYSIOLOGY 



335 



one-way valves all the expired air is collected. At the end of the period 

 of collection the air in the bag is carefully measured by means of an 

 accurately calibrated meter (a sample being drawn off for analysis 

 during the process of measurement), note being taken of the temperature 

 and the barometric pressure. The sample of air is analysed in the 

 Haldane gas analysis apparatus and. the percentage of oxygen and 

 carbon dioxide present determined. 



The total volume of carbon dioxide excreted and of oxygen taken in 

 has now to be calculated at C. and 760 mm. pressure. As the 

 volume of expired air has been measured moist it is necessary to ascer- 

 tain its volume when dry. This calculation is rendered easy by the 

 use of a table devised by Haldane. If an example is taken explanation 

 will be easier. Let it be assumed that analysis showed the sample of 



