142 



PRACTICAL PHYSIOLOGY 



pushed throughout the intercostal muscles until the end comes to 

 lie in the thoracic cavity. Notice the negative pressure indicated in 



the manometer, which becomes 

 greater in inspiration and less in 

 expiration. Note the immediate 

 collapse of the lung on opening 

 the pleural cavity. 



CHAPTER XXXIX. 



THE CHEMISTRY OF RESPIR- 

 ATION. 



The Estimation of the Gases 

 in Inspired and Expired Air by 

 Haldane's Apparatus. The gas 

 is measured in the graduated 

 gas-burette A, provided with a 

 three-way tap. Surrounding the 

 gas-burette is a water-jacket. 

 The whole is supported by a 

 clamp and retort stand. The 

 gas-burette is connected by 

 pressure tubing to the levelling 

 tube B, which is held by a spring 

 clamp attached to the retort 

 stand. A and B contain mercury, 

 and by raising or lowering B gas 

 can be expelled from or drawn 

 into A. One of the connections 

 of the three-way tap is used for 

 taking in the sample, the other 

 connects the burette with an 

 absorption apparatus arranged 



&g in the figure 



B 



Fio.l25.-Haldanes gas analysis apparatus. 



The bulb E, filled with 20 per cent, caustic potash, absorbs C0 2 . The 

 bulb F, filled with alkaline pyrogallic acid solution, 1 absorbs 2 . The 



1 Dissolve 100 grms. of stick caustic potash in 50 c.c. of water. Add 10 grins, of 

 pyrogallic acid to this solution. The pressure in the burette is adjusted by using 

 the potash pipette as a pressure gauge and bringing the potash before every reading 

 of the burette to the mark M. In order to make the reading of the burette 



