In the wonderful story of the “Peau de Chagrin,” the hero becomes possessed of a magical wild ass’ skin, which yields him the means of gratifying all his wishes.  But its surface represents the duration of the proprietor’s life; and for every satisfied desire the skin shrinks in proportion to the intensity of fruition, until at length life and the last hand-breadth of the peau de chagrin, disappear with the gratification of a last wish.

Balzac’s studies had led him over a wide range of thought and speculation, and his shadowing forth of physiological truth in this strange story may have been intentional.  At any rate, the matter of life is a veritable peau de chagrin, and for every vital act it is somewhat the smaller.  All work implies waste, and the work of life results, directly or indirectly, in the waste of protoplasm.

Every word uttered by a speaker costs him some physical loss; and, in the strictest sense, he burns that others may have light—­so much eloquence, so much of his body resolved into carbonic acid, water, and urea.  It is clear that this process of expenditure cannot go on for ever.  But, happily, the protoplasmic peau de chagrin differs from Balzac’s in its capacity of being repaired, and brought back to its full size, after every exertion.

For example, this present lecture, whatever its intellectual worth to you, has a certain physical value to me, which is, conceivably, expressible by the number of grains of protoplasm and other bodily substance wasted in maintaining my vital processes during its delivery.  My peau de chagrin will be distinctly smaller at the end of the discourse than it was at the beginning.  By and by, I shall probably have recourse to the substance commonly called mutton, for the purpose of stretching it back to its original size.  Now this mutton was once the living protoplasm, more or less modified, of another animal—­a sheep.  As I shall eat it, it is the same matter altered, not only by death, but by exposure to sundry artificial operations in the process of cooking.

But these changes, whatever be their extent, have not rendered it incompetent to resume its old functions as matter of life.  A singular inward laboratory, which I possess, will dissolve a certain portion of the modified protoplasm; the solution so formed will pass into my veins; and the subtle influences to which it will then be subjected will convert the dead protoplasm into living protoplasm, and transubstantiate sheep into man.

Nor is this all.  If digestion were a thing to be trifled with, I might sup upon lobster, and the matter of life of the crustacean would undergo the same wonderful metamorphosis into humanity.  And were I to return to my own place by sea, and undergo shipwreck, the crustacean might, and probably would, return the compliment, and demonstrate our common nature by turning my protoplasm into living lobster.  Or, if nothing better were to be had, I might supply my wants with mere bread, and I should find the protoplasm of the wheat-plant to be convertible into man, with no more trouble than that of the sheep, and with far less, I fancy, than that of the lobster.