6/2 THE POPULAR SCIENCE MONTHLY.
sistence ; it is tlieirs, as the chosen ministers of the higher ethics, on the one hand, to counteract the life-destroying checks which operate chiefly on the feeble and incompetent, and, on the other, to inculcate the prudential considerations which are most influen- tial with the finest types of mankind. No doubt the wider scope which modern science has given to medical practice enables those who pursue it to render services to the strong as well as to the weak, and to compensate in some degree for the general lowering of vitality which the maintenance of sickly lives tends to produce. Sanitary improvements and the removal of many of the causes of disease not only keep the infirm alive but insure increased vigor to the constitutions of the robust. But still the result of medical work as a whole at the present time must tend toward the intensification and the thwarting of the struggle for existence and perhaps to some deterioration of the species, for medical work does intermeddle with Nature's rough and ready methods in selecting her breeders. Great numbers of weakly infants who would formerly have perished in their infancy are now reared to a weakly maturity and enabled to propagate their weakliness (for the weakly are often highly prolific), while they take part in the life battle on terms sometimes made unduly favorable to them by the commiseration that their weakliness commands ; and this fact ought not to be lost sight of when we are congratulating our- selves on our greatly diminished death-rate. An enormous sav- ing of life has been effected, but mainly in life's earlier decades. The death-rate is actually increasing among males at all ages above thirty-five and among females at all ages above forty-five ; and it is not difficult to prove that this increased mortality at post-meridian ages is due partly to the enhanced wear and tear of modern existence and partly to the survival of weakly lives arti- ficially protected and prolonged.
The origin of those moral sentiments which, in the case of our race, are modifying the course of natural selection and which have evoked and molded the profession to which we belong is as inscrutable as the invention of natural selection itself, but their development has some light thrown on certain of its stages by biological considerations. In the life history of living organisms we can trace out some rudimentary phases of a new struggle for existence, a struggle between ethical princij^les and animal pro- pensities, a struggle that has to be fought out in the brain and mind of man, but that is foreshadowed in paltry protoplasmic particles. For very early in organization may ethical rudiments be detected ; indeed, the moment we get beyond the solitary cell, a simple organism which merely feeds and grows and liberates superfluous parts of its substance to start new organisms like itself, mutual obligation or what might be called a moral relation