Fitness is a complicated condition and not a simple one. It depends upon so many external conditions. Fitness in one place would be unfitness in another. Still, other things being equal, strength of constitution is a very important factor, and must not be left out of consideration. With it there is a surplus of material in the body beyond what is required for digestion, assimilation, circulation and other bodily functions, to enable the parents not only to do hard labor, but also to endow their offspring with vigor equal to their own, often greater vigor. The feeble individuals will have a small amount of stored up material in their bodies which we may designate as physiological capital to give continuous food, warmth and protection to their young; they will not be so well adjusted to their environment, and, consequently, natural selection will cause their non-survival--or their offspring, if not immediately, at no distant period. This doctrine of natural selection has been designated as cruel, harsh, inexorable, and under the influence of the human feeling every effort is in our time being made to prevent this wholesome check upon the processes of nature from having its due influence upon evolution and race progress. Modern hygiene undertakes to put an end to disease, to save all who are born, to surround them with every influence which can favor their health and development. It would stamp out diphtheria, scarlet fever, summer complaint, consumption and a host of other diseases which now decimate the ranks of the unfit, and often, no doubt, of the comparatively fit. This would perpetuate a type of feeble, unhealthy persons. There would not be much hope of more perfect health for the race if our hygienists could carry out this daring scheme along the lines now working. There seems an antagonism between nature's methods of bettering the physical condition of the race and the efforts of man himself, acting under the guidance of his moral feelings, to prevent the action of natural law. Mr. Darwin recognized this, and referred to it in his great work, "The Descent of Man," where he says: "With savages, the weak in body and mind are soon eliminated, and those that survive commonly exhibit a vigorous state of health. We civilized men, on the other hand, do our utmost to check the process of elimination. We build asylums for the imbeciles, the maimed and the sick; we institute poor laws; and our medical men exert their utmost skill to save the life of every one to the last moment." "There is," says he, "reason to believe that vaccination has preserved thousands who from a weak constitution would have succumbed to smallpox. Thus the weak members of civilized communities propagate their kind. No one who has attended to the breeding of domestic animals will doubt but this must be highly injurious to the human race. Excepting in the case of man himself hardly any one is so ignorant as to allow his worst animals to breed."