How often had his studies led him to dissect the bodies of animals that had died in their dens in the Jardin des Plantes!  Often in the first generation of cage-life, almost always in the second, invariably in the third, they grow dull, listless, the fire goes out of their eyes, the litheness out of their limbs:  they forget to eat, they cough, and soon they die.  Of what?  Consumption.  Once our fathers were wild and lived in the open air:  they scarcely ever died, as we do, of consumption.  Crowded cities, bad drainage, overwork, want of healthful exercise, stimulating food, dissipation,—­these are human cage-life.  If a man is threatened with consumption, let him go back to the plains and forests before it is too late.

Certainly the treatment benefited Fournier.  By and by it did more—­it cured him.  The cough was forgotten, the cheeks filled out, the muscles became hard as bundles of steel wire, his strength was prodigious:  he ate his food with a relish unknown in Paris, and slept like a child.

Nevertheless, his mind, trained to habits of thought and observation, was not idle.  When a city was his home he had been a physiologist and had studied man:  he made the world his dwelling-place, and wandering among the nations he became an ethnologist and began to study men.

A distinguished professor, writing of the influence of climate upon man, for the sake of illustration supposes the case of a human being whose life should be prolonged through many ages, and who should pass that life in journeying slowly from the arctic regions southward through the varying climates of the earth to the eternal winter of the antarctic zone.  Always preserving his personal identity, this traveler would undergo remarkable changes in form, feature and complexion, in habits and modes of life, and in mental and moral attributes.  Though he might have been perfectly white at first, his skin would pass through every degree of darkness until he reached the equator, when it would be black.  Proceeding onward, he would gradually become fairer, and on reaching the end of his journey he would again be pale.  His intellectual powers would vary also, and with them the shape of his skull.  His forehead, low and retreating, would by degrees assume a nobler form as he advanced to more genial climes, the facial angle reaching its maximum in the temperate zone, only to gradually diminish as he journeyed toward the torrid, and to again exhibit under the equator its original base development.  As he continued his journey toward the south pole he would undergo a second time this series of progressing and retrograding changes, until at length, as he laid his weary bones to rest in some icy cave in the drear antarctics,

    Multum ille et terris jactatus et alto,

he would be in every respect, save in age and a ripe experience, the same as at the outset of his wanderings.

Extravagant as this illustration may appear, the professor goes on to say, philosophically, on the doctrine of the unity of the human race, it is not so; for what else than such an imaginary prolonged individual life is the life of the race?  And what greater changes have occurred to our imaginary traveler than have actually befallen the human family?