62 ANSWERS TO PRACTICAL QUESTIONS 



the carbonic acid gas bears to the oxygen ; there being a smaller 

 quantity of oxygen and a greater quantity of carbonic acid, in 

 venous than in arterial blood. And it may be experimentally 

 demonstrated that this difference in their gaseous contents is 

 the only essential difference between venous and arterial blood. 

 For if arterial blood be shaken up with carbonic acid, so as to 

 be thoroughly saturated with that gas, it loses oxygen, gains 

 carbonic acid, and acquires the hue and properties of venous 

 blood ; while, if venous blood be similarly treated with oxygen, 

 it gains oxygen, loses carbonic acid, and takes on the color and 

 properties of arterial blood. HUXLEY'S Lessons in Physiology. 



. Do we need more O in ^v^nter than in summer ? 



Yes, if we are much exposed to the open air, and forced to 

 take abundant exercise in order to keep warm. 



5. Wliicli would starve sooner, a fat man or a lean 

 one ? 



The lean one. A superabundance of flesh, in a time of 

 scarcity, is taken up by the absorbents and thrown into the 

 circulation, thus supplying the place of food in nourishing the 

 body. 



6. How do teamsters ^varm themselves by slapping 

 their hands together' ? 



This exercise promotes the circulation of the blood, and its 

 oxidation is thus quickened. 



7. Could a person commit suicide by holding his 

 breath ? 



Respiration is entirely independent of consciousness, as is 

 seen in sleep, coma, etc. It may be interrupted for a few min- 

 utes, but no effort of the will can enable one to hold his breath 

 until life is extinct. The desire for O, the besoin de respirer, or 

 the respiratory sense, as it is called, becomes at last so great 

 that the strongest resolution yields the struggle. 



8. Wiy do we die ivhen our breath is stopped ? 



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

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



