The same vicarious system is manifest in the well-known examples, where the loss of one or more of the senses gives increased acuteness to the rest. The sense of touch, for instance, in the blind man, has sometimes proved no mean substitute for eyes; and, indeed, any of the senses by cultivation, in peculiar exigencies, may be prodigiously strengthened.
Now, in all these cases, where the vicarious principle is brought into operation, or sympathy concentrates the power of many organs in one, or the loss of one organ or sense quickens the sensibility of the rest, do we not recognize the prospective care and kindness of infinite benevolence? Do you say that it merely shows infinite wisdom, which adjusts means to ends with consummate skill, in order to be sure of success in its designs? Why, then, I inquire, should these provisions for trying exigencies in the animal system always tend to the happiness of the creature? Surely there were other means at the command of infinite wisdom for securing the existence of the animal, which would bring misery upon it instead of happiness. The benevolent tendency of the design, therefore, proves the benevolent feelings of the designer.
The extraordinary provisions that are made in some cases for the multiplication of animals and plants, in order to prevent the extinction of any races, and to give life and happiness to as many animals as can be sustained, is another indication of benevolent care on the part of the Creator. Not less than five modes of reproduction are known to exist, viz., the viviparous, the ovo-viviparous, the oviparous, the gemmiparous, and the fissiparous; and among the lowest families of animals several of these modes exist in the same species, so that their extinction, or even deficient multiplication, is scarcely possible.
The same benevolence is manifested in the power possessed by animals and plants to adapt themselves to different circumstances. Often are they thrown into conditions widely diverse as to food, temperature, and exposure to chemical and mechanical agencies, with no possibility on their part of avoiding them. This is eminently true of man; and were not animals able to adapt themselves to these various states, they must perish. True, there are limits to this adaptation; but they are wide enough to accomplish the great purposes of existence, and to make us comfortable and happy amid great changes in our condition. Nor is this power of adaptation among animals limited to their physical nature. Their mental habits admit of an oscillation equally wide, so that, ere long, we become happy in a condition which at first was painful in the extreme. New habits take the place of the old ones so gradually that we scarcely realize the change.