18 THE HAKVEIAN ORATION, 1894 



exertion is over-continued it may lead to permanent mischief. 

 More especially is this the case in young growing boys, and it 

 is not merely foolish, it is wicked to insist upon boys engaging 

 in games or contests which demand a long-continued over- 

 exertion of the heart, such as enforced races and paper-chases 

 extending over several miles. Intermittent exertion, either of 

 a single muscle or of a group of muscles, or of the whole body, 

 appears to lead to better nutrition and increased strength and 

 hypertrophy, but over-exertion, especially if continuous, leads to 

 impaired nutrition, weakness and atrophy. If we watch the 

 movements of young animals, we find that they are often rapid, 

 but fitful, irregular and varied in character, instead of being 

 steady, regular and uniform. They are the movements of the 

 butterfly, and not of the bee. The varied plays of childhood, 

 the gambols of the lamb, and the frisking of the colt, are all 

 well adapted to increase the strength of the body without doing 

 it any injury ; but if the colt, instead of being allowed to frisk 

 at its own free w^ill, is put in harness, or ridden in races, the 

 energy which ought to have gone to growth is used up by the 

 work, its nutrition is affected, its powers diminished, and its life 

 is shortened. The rules which have been arrived at by the 

 breeders of horses ought to be carefully considered by the 

 teachers of schools, and by the medical advisers who super- 

 intend the pupils. 



In youth and middle age every organ of the body is adapted 

 for doing more work than it is usually called upon to do. 

 Every organ can, as it is usually termed, "make a spurt" if 

 required ; but as old age comes on this capacity disappears, the 

 tissues become less elastic, the arteries become more rigid and 

 less capable of dilating and allowing a freer flow of blood to any 

 part, whether it be the intestine, the skin, the brain, the 

 muscles, or the heart itself. Mere rigidity of the arteries 

 supplying the muscles of the heart will lessen the power of 

 extra exertion, but if the vessels be not only rigid, but diminished 

 in calibre, the muscles of the limbs ^nd the heart itself will be 

 unfit even for their ordinary work, and will tend to fail on the 

 slightest over-exertion. This fact was noticed by Sir Benjamin 

 Brodie, who, when speaking of patients with degenerating and 



