Those nations which expend the most energy are probably the ones among whom longevity is greatest and the mortality rate the lowest. In the city of Chicago there are many conditions adverse to health of body and mind, yet the city is famous for its relatively low mortality as a parallel fact. It is also affirmed that the average Chicago man works longer hours and actually accomplishes more than the average man elsewhere. This excess in the expenditure of energy--in so far as it is wisely spent--may be one of the reasons for the excellent health record of the city. In every walk of life we see that the race is not to the swift nor the battle to the strong. We all know men clearly of secondary ability who nevertheless occupy high positions in <p 22> business and state. We are acquainted also with men of excellent native endowment who still have never risen above the ranks of mediocrity. _Human efficiency is not measured in terms of muscular energy nor of intellectual grasp. It is dependent upon many factors other than native strength of mind and body_. The attitude which one takes toward life in general and toward his calling in particular is of more importance than native ability. The man with concentration, or the power of continued enthusiastic application, will surpass a brilliant competitor if this latter is careless and indifferent towards his work. Many who have accomplished great things in business, in the professions, and in science have been men of moderate ability. For testimony of this fact take this striking quotation from Charles Darwin. ``I have no great quickness of apprehension or wit, which is so remarkable in some clever men,'' he writes. ``I am a poor critic. . . . My power to follow a long and purely abstract <p 23> train of thought is very limited; and therefore I never could have succeeded with metaphysics or mathematics. My memory is extensive, yet hazy; it suffices to make me cautious by vaguely telling me that I have observed or read something opposed to the conclusion which I am drawing, or on the other hand in favor of it. So poor in one sense is my memory, that I have never been able to remember for more than a few days a single date or a line of poetry. I have a fair share of invention, and of common sense or judgment, such as every fairly successful lawyer or doctor must have, but not, I believe, in any higher degree.'' This is presumably an honest statement of fact, and in addition it should be remembered that Darwin was always physically weak, that for forty years he was practically an invalid and able to work for only about three hours a day. In these few hours he was able to accomplish more, however, than other men of apparently superior ability who were able to work long hours daily for many <p 24> years. Darwin made the most of his ability and increased his efficiency to its maximum.