Payment may assume a penal form: do not think this its only form. And to take the law at once out of the limitations which these examples suggest, let me show you that it is a law of healthy and unlamenting Nature. Look at the scale of existence, and you will see that for every step of advance in that scale payment is required. The animal is higher than the vegetable; the animal, accordingly, is subject to the sense of pain, the vegetable not; and among animals the pain may be keener as the organization is nobler. The susceptibility not only to pain, but to vital injury, observes the same gradation. A little girdling kills an oak; but some low fungus may be cut and troubled and trampled ad libitum, and it will not perish; and along the shores, farmers year after year pluck sea-weed from the rocks, and year after year it springs again lively as ever. Among the lowest orders of animals you shall find a creature that, if you cut it in two, straightway duplicates its existence and floats away twice as happy as before; but of the prick of a bodkin or the sting of a bee the noblest of men may die.
In the animal body the organs make a draft from the general vigors of the system just in proportion to their dignity. The eye,—what an expensive boarder at the gastric tables is that! Considerable provinces of the brain have to be made over to its exclusive use; and it will be remembered that a single ounce of delicate, sensitive brain, full of mysterious and marvellous powers, requires more vital support than many pounds of common muscle. The powers of the eye are great; it has a right to cost much, and it does cost. Also we observe that in this organ there is the exceeding susceptibility to injury, which, as we have observed, invariably accompanies powers of a lofty grade.