man is of that nature, is remarkable. If, hearing Bismarck called a man of iron, one should analyze his remains to find out how much more iron he contained than ordinary men, it would be a performance exactly comparable to Mr. Redfield's, when he thinks of a man's "energy" as something stored up by
As a fact, a man contains less energy, after the performance of work, than he did at the start. All of his "energy" comes from the metabolism of food that he has previously eaten. His potential energy is the food stored up in his body, particularly the glycogen in the liver and muscles.80
Why, then, can one man run faster than another? Mr. Redfield thinks it is because the sprinter has, by previous work, stored up energy in his body, which carries him over the course more rapidly than the sluggard who has not been subjected to systematic training. But the differences in men's ability are not due to the amount of energy they have stored up. It is due rather to differences in their structure (using this word in a very broad sense), which produce differences in the efficiency with which they can use the stored-up energy (i.e., food) in their bodies. A fat Shorthorn bull contains much more stored-up energy than does a race horse, but the latter has the better structure—coördination of muscles with nervous system, in particular—and there is never any doubt about how a race between the two will end. The difference between the results achieved by a highly educated thinker and a low-grade moron are similarly differences in structural efficiency: the moron may eat much more, and thereby have more potential energy, than the scholar; but the machine, the brain, can not utilize it.
The effects of training are not to store