152 PHYSIOLOGY AND NATIONAL NEEDS 



for the efficient removal of carbon dioxide and the 

 necessary absorption of oxygen. Athletes and the 

 trainers of racehorses and greyhounds have learnt 

 from experience the correct way to train the heart. 

 That organ is a muscle and must be trained by 

 progressive work. Its rate of contraction varies in 

 different healthy men ; it may be fifty or seventy 

 beats per minute during rest. There is no uni- 

 formity in rate, but in all men there is a response 

 to exercise, an increase, it may be, to one hundred 

 and sixty beats per minute. The man with the 

 slow pulse at rest has a greater range before he 

 reaches the speed-limit of the heart during severe 

 muscular work. It has been found that many of 

 the best athletes have a very slow pulse during rest, 

 and the general effect of progressive muscular 

 exercise is to produce a slow beat of the heart 

 during rest and a more rapid return to this rate 

 after strenuous exercise. A weak heart is not made 

 stronger by the avoidance of muscular work; it 

 should be exercised by slowly increasing the amount 

 of work. 



Physiological knowledge agrees with sound ex- 

 perience, for the latter is in reality the result of 

 numerous physiological experiments ; but they are 

 equally in conflict with the erroneous ideas of some 

 authors of systems of physical training, who by 

 drill movements aim at expanding or opening out 

 the chest in order, as they say, to give the heart 



