Nature's Teachings: Human Invention Anticipated by Nature

by J. G. Wood

Next comes the principle of the lever, as exemplified by the handles of the scissors. By lengthening these handles, the power of the blades is enormously increased, as may be seen in the various shears in any great iron-works, which cut through thick iron as if it were butter. Our own garden shears for trimming borders show very well the power of the long arms and short blade.

In the animal world we find many examples of natural shears, one of the best of which is afforded by the jaws of the Tortoise or Turtle. Owing to the manner in which they feed, whether they be vegetarians or carnivorous, their jaws are made for cutting, and not for lacerating or mastication. They have no teeth, but each jaw is furnished with a horny edge, as sharp as a knife-blade, and very strongly made. With these jaws the animal can shred to pieces the objects which it attacks, just as if it had been furnished with a pair of veritable shears. Any one who has possessed an ordinary Tortoise must have noticed the havoc which it will occasionally make in a garden. I had one of these reptiles for some years, and was obliged to keep it under restraint, in consequence of the power of its jaws.

Being a Tortoise of discrimination, it took a great fancy to the strawberry beds, and invariably picked out the ripest and best-flavoured fruit. Reversing the usual proverb of making two bites at a cherry, the Tortoise always took two bites at a strawberry, and sometimes three or four, according to its size.

At last, I was obliged to restrain it by boring a hole in the edge of its shell, passing one end of a string through it, and fastening the other to a peg driven into the ground. At first, I tied the string to a brick, but the Tortoise was so strong that it dragged the brick about the garden, leaving reminiscences of its progress in the channels which it had cut through all kinds of vegetation with its scissor-like jaws.

The reader, in comparing the illustration of the Turtle-jaws with that of the Shears, will see at once how exact is the analogy between the two. The sharp-edged jaws correspond with the blades of the shears, the joint at the skull corresponds with the pivot of the shears, and the muscles which move the jaws, but which could not be shown in the present illustration, are the prototypes of the handles.

In some of these creatures, especially those which are carnivorous, the power of the jaw is tremendous. One of them, a Snapping Turtle, has been known to bite off several fingers of a man’s hand as easily as if they had been carrots. Some years ago I kept some Chicken Tortoises alive, and was much struck with the enormous proportionate power of their jaws.

They were quite little creatures, only a few inches in length, but their appetites were astonishing, and their mode of satisfying their hunger remarkable. They were always ravenous after meat, and had a curious way of seizing their food in their mouths, placing one paw on either side of their jaws, and then pushing the meat forcibly away, so as to cut out a slice as large as their jaws.

They were very good-tempered little things, but, small though they were, I should have been very sorry to have one of them take a bite at my finger by mistake.

Knowing their general characteristics, I took care not to have any living creature in the same vessel. But I have heard, from those who have had practical experience, that Chicken Tortoises ought to be banished from any place wherein fish are kept, especially if they be gold fish, the Tortoise having a way of coming quietly beneath them, biting out a mouthful of their bodies, and then disappearing with its booty.