Nature's Teachings: Human Invention Anticipated by Nature

by J. G. Wood

On the right hand of the illustrations we see three cutting tools made by human hands—i.e. the Chisel, the Stone Adze of Polynesia, and the Steel Adze of this country. We begin with the Chisel.

All those who have even a slight knowledge of anatomy know how curiously exact is the resemblance of the Chisel of civilised life to the front tooth of any Rodent animal. The head of the Beaver is here given as an example, but the tooth of a mouse, rat, or rabbit, which can easily be obtained, is quite as good an example. These teeth are made after a very beautiful fashion. Their outer surface is covered with a plate of very hard enamel, while the rest of the tooth is of bony matter, and comparatively soft. Consequently, when the tooth is used, the enamel plate forms a sharp edge, while the rest of it is worn away, thus keeping the chisel-like end in its proper form.

The power of these teeth may be appreciated by any one who has been bitten even by so small a rodent as a mouse, the sharp edges meeting in the flesh, and causing a very painful wound. When the teeth are large, as in the Beaver, and the jaws powerful, their force is something wonderful, tree-trunks of considerable size being cut down quite easily.

Perhaps some of my readers may not be aware that the Chisel is constructed on exactly the same principle as the tooth of the Rodent animal. It is not entirely made of steel, as is generally thought. In the first place, a valuable material would be needlessly wasted, and, in the next place, the tool would not keep its edge except with infinite labour in grinding.

The principal part of the Chisel-blade is therefore made of soft iron, a very thin plate of steel running along the back. This plate answers the same purpose as the enamel in the tooth, while the soft iron takes the place of the soft bone. Axe-blades, which are, in fact, formed like two chisels placed back to back, are made on a similar principle, except that the steel plate occupies the centre of the blade, and the soft iron is on either side. Thus the thin plate of steel is easily brought to an edge, while the soft iron can be ground away without any difficulty.

I do not mean to state that the inventor of this combination of thin steel and soft iron had taken his idea from the Rodent tooth, but only to show that the invention, beautiful, simple, and ingenious as it is, has its prototype in Nature. I may here mention that the Plane-iron, which is, in fact, a modified Chisel, is made in exactly the same fashion.

Next we come to the Adze.

In some respects there is much resemblance between the blade of the Adze and the teeth of the Rodent, especially in their curve, which is almost identical in both. This form is seen in the structure of other teeth than those of Rodents. There is, for example, the tooth of the Hippopotamus, which is not only curved, like that of the Rodent, but bevelled off in a similar way at the tip. With these formidable teeth, one of which is now before me, the Hippopotamus makes terrible havoc among the herbage, mowing it down, so to speak, and stowing it away wholesale in its enormous stomach. A Hippopotamus indeed, when angered, has been known to sever a man’s body completely in two with a single bite, so trenchant are the teeth, and so powerful the jaws.