154 PHYSIOLOGY AND NATIONAL NEEDS 



becomes giddy and stops breathing. Another result 

 of this exercise, performed in a school-room, is 

 that the spray of the breath containing any in- 

 fectious germs, which may be present in the throats 

 of some members of the class, is spread broadcast 

 and is inspired by others. It is no wonder that 

 compulsory education and breathing exercises have 

 coincided with numerous epidemics among school 

 children. 



Healthy children do not require teaching how to 

 breathe ; they are trained unconsciously by their 

 running in the open air. Athletes and the trainers 

 pf racehorses have learnt by experience the correct 

 way to train the lungs. By progressive muscular 

 exercise the respiratory system is stimulated in the 

 natural manner ; the activity of the muscles during 

 running produces a great output of carbon dioxide 

 and uses up much oxygen, the nervous system 

 responds to the changes in the composition of the 

 blood, and the respiratory muscles contract more 

 frequently and forcibly. A further advantage is 

 that the heart is stimulated and trained at the 

 same time. 



Gymnastic exercises have been devised for the 

 purpose of expanding the chest. The result may 

 be seen in soldiers, who tend to fix their chests in 

 a partly distended condition. The increased girth 

 of the chest produced in this way is often only 

 apparent, and is due in some cases to a special 



