Shears and Scissors.
These instruments are sure signs of civilisation, no savage nations having the least idea of them. Even the Kafir and Esquimaux tribes, which are such admirable workers in skin, never use scissors in shaping their garments, but invariably employ knives for that purpose. The Chinese, however, seem to have known scissors from time immemorial, and to have shaped them almost exactly like our own instruments. I possess one pair of tailor’s shears from China in which there is only one ring, namely, that for the thumb. The place of the other ring is taken by an elongated, slightly curved and moderately pointed rod of steel, which is used for tracing the pattern on the material preparatory to cutting it.
Simple as the scissors may seem, they combine several very important principles, namely, the inclined plane, the lever, and the cutting edge. Were they to be merely two edges moving directly upon each other, their effect would be comparatively slight; but, owing to the manner in which the blades are fixed at one end, they are drawn as it were over the object between them, and so divide it with comparative ease. In some instruments, such as the pruning scissors, there is only one cutting blade, the other being used merely as a support for the branch which is being cut.
A well-known example of a single cutting blade is found in the guillotine. In the earliest times of this invention an ordinary axe-head was suspended above the neck of the criminal. It was found, however, that its operation was very uncertain, simply because the blow was a direct one, and not oblique. The blade was then set obliquely, as in the present machine, and its effect was absolutely certain.
Perhaps some of my readers may be swordsmen, and therefore know the power of the “drawing cut,” by which a great effect may be produced with very little apparent exertion. Even in the simple operation of cutting bread we always use the knife diagonally, though perhaps we may be ignorant of the principle of the inclined plane.
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.
Beside the Tortoise, there are many creatures which possess natural shears, such as the Locust, whose ravages are only too notorious. Then, taking our own country, we have plenty of examples of insect shears. Such is to be found in the jaws of the Cockchafer larva, or “White Grub” as it is popularly called. It lives underground, and feeds chiefly on the roots of herbage, shredding them to pieces with its shear-like jaws. And, as it spends on the average three years in the one task of perpetual eating, the damage which it does can be easily imagined.
There is a very pretty English insect which admirably exemplifies the power of the natural scissors. This is the Great Green Grasshopper (Acrida viridissima), which is equally voracious in all its stages of existence. It is always ready to use these jaws, and I do not recommend the reader to allow his finger to get between them, or their points will probably meet.
One of these insects, indeed (Decticus griseus), has derived the name of Wart-biter from its supposed use in curing warts. All that was needful was to catch a Wart-biter, and hold one of the warts to its jaws. It was sure to seize the wart, and bite it smartly, and there was a firm belief that any one thus bitten would be freed from the unsightly excrescence. The bite of the shear-like jaws caused much pain at the time, and this very pain had in all probability something to do with the cure.
An admirable example of the insect jaws used as scissors is to be found in the well-known Leaf-cutter Bees, insects belonging to the genus Megachile.
They make their nests in burrows, sometimes in wood, and sometimes in the ground, and form them in a very singular manner. After fixing upon a suitable burrow, the Bee goes off to a tree, generally a rose, and, using her jaws just as a tailor uses his shears, cuts off a nearly semicircular piece of leaf, flies away with it to her home, and, by dint of bending, pushing, and pulling it, she forces it to the bottom of the cell. Successive pieces of leaf follow, until she has made a thimble-shaped cell, and she then places at its end an egg and a supply of honey and pollen.
Cell after cell succeeds, each being introduced into its predecessor just as thimbles are packed. Judging from a specimen in my collection, there are about eight layers of leaves to form the walls of the cell, and the average length of each piece of leaf rather exceeds half an inch. The entire length of the cell-group is two inches and a half. The leaf-slices are always cut from the edge, and, in my specimen of the nest, the serrated outer edges of the leaves are all in one direction.
Should any of my readers find one of these nests, it will be as well for them to dip a needle point into diamond cement, and introduce it under the outermost coating of leaves. Otherwise, when the leaves are dry, and the insects break their way into the open air, the cells will probably fall to pieces.
These Bees are much more abundant than is usually thought. In summer-time it is hardly possible to find a rose-bush on which are not a number of leaves from which pieces of variable size and shape, but always with a curved outline, have been cut as with scissors. While cutting them, the Bee seems to trace out her pattern, as it were, by using her feet like one leg of a pair of compasses, and her head as the other leg. As soon as she has nearly finished the operation, she poises herself on the wing, to prevent her weight from tearing away the leaf irregularly, and then, while still on the wing, makes the last few bites, and severs the leaf entirely.