IO2 Physiology. 



is this now known to be from the real facts of the case 

 that it is well established that the use of alcoholic drinks 

 makes the body less able to resist the germs of consump- 

 tion. Under the former mistaken view many consump- 

 tives used alcoholic liquors to their own injury. But time 

 and experience have taught that they only increase the 

 trouble. 



Summary. i. In the lungs the air and blood are brought very close 

 together, only the wall of the capillary and that of the air vesicle being 

 between them. 



2. Through these two layers oxygen passes from the air sac into the 

 blood. Carbon dioxid, water vapor, and other wastes pass' from the 

 blood into the air sac. 



3. The mucous membrane of the air passages secretes mucus which 

 is driven toward the nostrils by the ciliums. 



4. The chest is lengthened by the lowering of the diaphragm, and 

 widened by the lifting of the ribs, giving greater space, which is filled 

 by external air expanding the lungs. 



5. Inspiration requires extra effort; but ordinary expiration is with- 

 out effort because of the elastic reactions. 



6. Forced expiration, as coughing, requires active muscular effort. 



7. The vital capacity may be increased by practice and by exercise. 



8. We should breathe through the nose, not through the mouth. 



9. Respiration is under the control of the nervous system. 



Questions. I. Is it well to see how long one can hold his breath ? 



2. Should the head be covered by bedclothes ? 



3. How is respiration affected by a stooping posture ? 



4. What are the "lights" of an animal ? 



5. Of what advantage is it that the cartilages of the windpipe are 

 C-shaped, and not complete rings ? 



6. From the statements in this chapter of the amount of air taken in 

 at each breath and of the rate of breathing, find out how much air is 

 breathed in an hour. How much in twenty-four hours ? 



