1 66 ELEMENTS OF PHYSIOLOGY 



contracted breathing, of removing pressure from the heart 

 and large blood vessels in the chest, and allowing the heart 

 to work with greater freedom. It also keeps the lungs 

 more expauded. You learned in another paragraph that 

 it is the usual method of quiet breathing; but strong, 

 contracted breathing sends out fouler air from deep in the 

 lungs. 



276. In both of these ways of using the breathing mus- 

 cles, there is a pause in the neutral position before the 

 next breath. But in a time of great exertion, as when 

 running, or during a time of excitement and in some forms 

 of illness, there is no pause between breaths, and we use 

 what may be called continuous breathing. Both when ex- 

 piring and inspiring, the ribs are pulled on beyond the 

 position at which they rest. Thus the use of the breath- 

 ing muscles is continuous, and it is no wonder that they 

 may get so tired that they almost refuse to work for a 

 moment, and we are "out of breath," as we say. The 

 heart is thumping so fast and strong that the corpuscles 

 are shot through the lungs with unnecessary speed and do 

 not get even as much oxygen as they would if going more 

 slowly. Continuous breathing is a wasteful method ; haste 

 makes waste of strength, although it may seem to be 

 necessary in an emergency. You can really accomplish 

 more by quiet, steady work. Anxiety and worry, as well as 

 great physical exertion, cause this hurried, wasteful breath- 

 ing ; hence we should cultivate the easy way of breathing. 



277. Reasons for Strong Expiration and Inspiration. 

 Purifying the air in the lungs may be illustrated by dipping 

 dirty water out of a barrel and replacing it with clear water. 

 If a dipperful of clean water is poured into the barrel and 

 the same amount of water is dipped out, this will cause the 

 cleanest water to be at the top, whence it will always be 

 dipped out and the dirtiest water will be left. It is the same 

 way with the lungs ; the purest air in the lungs is always 



