MEASUREMENTS 316 



By placing the cock in the third position and lifting B ', the air 

 in B is driven into the test tube E. The first bubbles of gas should 

 be allowed to escape outside the test tube so as to insure that 

 RA ' is filled with expired gas only. 



FIG. 224. Apparatus for sampling and measuring respiratory gases 



(J. Amar). 



Whilst these operations are proceeding all the rest of J the 

 expired gases pass to the spiromerer S, which indicates the quan- 

 tity. The average temperature of these gases is given by the 

 thermometer t. 



A very practical arrangement, for certain experiments, is to 

 take two connections from the vessel F. This is shown in figure 224, 



243. Analysis of the Gas. Suppose, for example, 150 cubic 

 centimetres of gas to have been retained in the test tube E, or a 

 sample to have been taken in Tissot's automatic spircmeter, and 

 that it is desired to analyse this sample. The two following eudi- 

 meters, can be employed for the purpose, both being charged 

 with reagents to absorb the carbonic gas and oxygen. 



1. Laulanies Eudiometer,^)- The usual and most practical 

 model consists of two glass vessels, K and P, the one containing 

 potash solution to absorb the carbonic gas ; the other phosphorus, 

 immersed in water, which has the property of rapidly fixing the 

 oxygen of the air. The two graduated tubes, m and g, serve, 



(*) Laulanie (Arch, de Physiol., 1894, p. 740). 



