no less than six—enumerated in Professor Owen's list may prove to be synonymous, and thus a new field of scientific research may become obscure at the very threshold of the enquiry.
In the history of every land there is a point at which the real merges in the ideal—at which fact is lost in fiction; and it is thus in the history of animals. That of the sloth commences with the publication of Waterton's ' Wanderings in South America;' all before that date is fable, or mixed with fable, all after it is fact; and the contrast is not greater between the humming-bird and the tortoise, than between the sloth of fact and the sloth of fiction. The history is familiar to every naturalist, or we should quote it. Let us turn to Dr. Lund's account of the living sloth.
"Inasmuch as the mechanism of the sloth's movements, so far as I am aware, is not very well known, I may take the liberty of recording the observations I made on the three-toed sloth (Bradypus torquatus) which I kept in my house for a considerable time. This animal climbs with remarkable sureness and aptitude, although, as is well known, with a degree of slowness which, however, may be called rapidity in comparison with its terrestrial movements. The manner in which it moves is this:—Lying on its belly, with a*ll its four extremities stretched out from its body, it first presses one of its hind feet with all its might against the ground, whereby the corresponding side of the body is a little raised. The fore-leg on the same side thus becomes sufficiently free for the animal to advance it a trifle forward. It then hooks its powerful claws fast in the earth, and so drags its body a little onwards. The same manoeuvre is next repeated on the opposite side; and thus the poor creature progresses in the slowest and most laborious manner possible. But this mode of progression requires certain conditions of the surface; for if it is not soft enough to admit the insertion of the claws, or if there are no inequalities for them to hold by, the sloth is completely deprived of the power of changing its position. For instance, when I laid it on a table of polished mahogany, it could not advance the least, notwithstanding all its exertions. But in proportion as the sloth's organization unfits it for terrestrial progression, is it wonderfully adapted to climbing trees. With its long arms it reaches high up, and clings fast to the branches with its strong crooked claws. The inverted position of the soles of its hind feet, gives it a power of grasping the trunk of the tree which no other mammal possesses. So that truly, when we see it climbing a tree, we can scarcely believe it to be the same animal that lies so helpless on the ground. Hence we see, that the sloth's organization is entirely adapted for living in trees. Compared with the slowness of its motions, it is the best climber among mammals, while it is the worst walker; or rather, it is the only mammal that can neither walk nor stand. These peculiarities depend on three principal points in its organization:—1st, the great length of its anterior extremities, in comparison with its posterior; 2diy, its powerful crooked claws; and 3dly, the irregular position of its hind feet."—Lund in Mag. Nat. Hist. New Series, iv. 158.
In this account there is much that is excellent, but we doubt whether the Doctor ever saw a sloth climbing a tree, except in imagination, or he would never have omitted to notice that it ran below instead of above the boughs, and thus effectually counteracted what he terms
