ELEMENTARY EXPERIMENTAL PHYSIOLOGY 



181 



possible to ren ler the pressure in N equal to that of the atmosphere. 

 At the beginning of the experiment the potash is adjusted to the mark 

 R by altering S, P being open. P is then closed, and not opened again 



B 



Flo. 179. Haldane's gas analysis apparatus. 



FIG. ISO. Hempel's burette for col- 

 lecting a sample of expired air. 



till the analyses are complete. The barometer and the temperature of 

 the water-jacket are read. Each time a reading of the burette is made 

 the potash is brought to the mark R by altering S, and to the mark M 

 by means of the levelling tube B. As the control tube and the gas- 



