140 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



in origin. Haldane considers it is unnecessary to assume the 

 existence of a vagus apncea in man at all under normal circum- 

 stances. It is, however, probable that in normal breathing the 

 nervous reflex and the chemical stimulus have both to be reckoned 

 with, though the relative importance of these two factors is a question 

 for the future. 



