Page:Popular Science Monthly Volume 3.djvu/619

Rh means of subsistence becomes greater; or some enemy of the species, multiplying in proportion to the abundance of its prey, becomes more destructive; or some disease, encouraged by greater proximity, becomes more prevalent. This general truth, everywhere exemplified among inferior races of beings, holds of the human race. True, it is in this case variously traversed and obscured. By emigration, the limits against which population continually presses are partially evaded; by improvements in production, they are continually removed further away; and, along with increase of knowledge, there comes an avoidance of detrimental agencies. Still, these are but qualifications of an inevitable action and reaction.

Let us here glance at the relation between this general truth and the legislative measures adopted to ward off certain causes of death. Every individual eventually dies from inability to withstand some environing action. It may be a mechanical force that cannot be resisted by the strengths of his bodily structures; it may be a deleterious gas which, absorbed into his blood, so deranges the processes throughout his body as finally to overthrow their balance; or it may be, and most frequently is, an absorption of his bodily heat by surrounding things that is too great for his enfeebled functions to meet. In all cases, however, it is one, or some, of the many forces to which he is exposed, and in presence of which his vital activities have to be carried on. He may succumb early or late, according to the goodness of his structure and the incidents of his career. But, in the natural working of things, those having imperfect structures succumb before they have offspring, leaving those with fitter structures to produce the next generation. And, obviously, the working of this process is such that as many will continue to live and to reproduce as can do so under the conditions then existing: if the assemblage of influences becomes more difficult to withstand, a larger number of the feebler disappear early; if the assemblage of influences is made more favorable, by the removal of, or mitigation of, some unfavorable influence, there is an increase in the number of the feebler who survive and leave posterity. Hence two proximate results, conspiring to the same ultimate result. First, population increases at a greater rate than it would otherwise have done: so subjecting all persons to certain other destroying agencies in more intense forms. Second, by intermarriage of the feebler who now survive, with the stronger who would otherwise have alone survived, the general constitution is brought down to the level of strength required to meet these more favorable conditions. That is to say, there by-and-by arises a state of things under which a general decrease in the power of withstanding this mitigated destroying cause, and a general increase in the activity of other destroying causes, consequent on greater numbers, bring mortality and fertility into the same relation as before—there is a somewhat larger number of a somewhat weaker race.