In reality this movement is achieved by an apparatus very similar in its action to that of the escapement. The rings, or “segments,” of which the body is composed, are furnished with rows of sharp points, arranged very like the cogs of the escapement wheel. By alternately elongating and contracting the body, these points catch against surrounding substances, and force the creature onwards, only allowing of movement in one direction.
Perhaps the reader will remember that in an earlier part of this work it has been mentioned that the various worms propel themselves by the same means. So do the Serpents, the edges of the scales serving the same purpose as the hairs of the worms and the hooks of the grub.
Union is Strength.
ON the left hand of the accompanying illustration we have an example of the wonderful power obtained by uniting together a number of comparatively weak objects. It represents a portion of the rope attached to the harpoon with which the natives of some parts of Africa attack and kill the hippopotamus.
Considering that a full-grown hippopotamus weighs several tons, and, in spite of its enormous size, is as active as a tiger, we can infer the strength of the rope which must be needed to hold such an animal when excited with rage and pain.
A few years ago the female hippopotamus at the Zoological Gardens, when deprived of her cub, actually tried to leap over the lofty iron barrier, and so far succeeded as to throw her weight on the uppermost bar. Fortunately it was made of well-wrought iron, and was only bent by her weight. Had it been made of cast-iron, like most railings, she would have snapped it like glass.
Now, the fibres of which the rope is composed are individually feeble, but, when they lend their strength to each other, their strength is amazing. It is well shown by a lasso in my possession, made of the fibres of the aloe-leaf. It is scarcely as thick as a man’s little finger, and yet it is strong enough to resist the efforts of the most powerful wild bull. I have some of the separate fibres, and it is interesting to notice how fibres so slight when separate should be so strong when united. Part of the rope has been unlaid, so as to show the manner in which it has been put together.
Towards the harpoon itself, a number of small cords laid loosely side by side are used, so as to prevent the hippopotamus from severing the rope with his chisel-like teeth, which he would assuredly do if it were single. The multitudinous cords become entangled among the teeth, and baffle his efforts; but still their unity is their strength; and, though the animal may sever one or two of them, the others retain their hold until he dies under a shower of spears.
On the right-hand side of the illustration is the Spinneret of the ordinary garden Spider, showing the many orifices from which the silken threads emerge. It is a remarkable point, and one which, I believe, is seldom noticed, that the Spider can at pleasure combine all these fibres into a single cord, or issue and keep them separate, just as is the case with the hippopotamus rope.