RESPIRATION 



)37 



respirations almost stop, but a sufficient gaseous interchange 

 is kept up by these cardio-pneumatic movements. 



(2) If, as is often the case in bronchitis, there is a plug of 

 mucus in a small bronchus near the heart, the rush of air past 

 it may give rise to a murmuring sound, in character very like 

 a cardiac murmur and synchronous with the heart's action. 



IV. Interchange between the Air breathed and the Blood 



in the Lung Capillaries. 



I. Effects of Respiration upon the Air breathed. — 1. Method 



Air 



PERCEhfT 



Blood, 



PerCent 



OF Gases 



4- 



B. 



F IG. 218. — A. Shows the Composition of Inspired and Expired Air. B. 

 Shows the Difference in the percentage Composition of the Gas of 

 Venous and Arterial Blood. 



of Investigation. — A measured quantity of air is collected in 

 a graduated burette. It is then forced into a chamber contain- 

 ing caustic potash, by which the CO^ is absorbed, and the 

 volume of air is asrain measured. It is next forced into a 

 chamber containing sodium pyrogallate in caustic soda, which 

 absorbs the 0„, and is again measured. The residue is 

 nitrogen. In this way the amount of the gases present is 

 determined {Practical Physiology). 



I 



