IN CHEMISTS Y. 89 



10. Why do we die when our breath is stopped 1 } 



" In asphyxia it is difficult to say which destroys life, 

 the absence of oxygen or the presence of carbonic acid." 

 FLINT. There is an absence of oxygen, so essential 

 to every vital operation, and also an accumulation of 

 carbonic acid * in the system. 



1 1. Why do we breathe so slowly when we sleep ? 



(See Chemistry, page 35.) 



Because so little muscular action is going on in the 

 body. 



12. How does a cold-blooded animal differ from a warm- 

 blooded one ? 



In the imperfection with which the blood is oxygenated. 

 The lungs are often of small capacity, and loose texture, 

 and are sometimes wanting entirely. In reptiles a por- 

 tion of the blood is not sent to the heart, and hence in 

 the vessels there is a mixture of arterial and venous 

 blood. The breathing is therefore slow, the motions are 

 languid, and there is little heat. 



13. Why does not the body burn out like a candle? 



Because it is renewed by the processes of assimilation 

 and nutrition as rapidly as it is destroyed by the waste 

 of oxidation. Whenever the former are in excess we 

 gain flesh, when the latter, we grow poor. 



14. Do all parts of the body change alike? 



* This gas remains fixed in the blood-corpuscles, and renders them inca- 

 pable of furnishing any oxygen to the system. CO is a deadly poison, 

 because it clings to the disks more tenaciously. 



