英文科學(xué)讀本 第五冊(cè)·Lesson 02 Man and Brute

Lesson 02 Man and Brute

Step by step our lessons have made us familiar, in some degree, with the build of the human body, and, through it, with the general structure of the various members of the brute creation. We are now in a position to carry our investigations a little farther, taking still the human body as the type, and following up, as we meet with them, the various adaptations of it to suit the requirements of each animal. Let us commence with the head, which, as you know, consists of two distinct parts—the skull and the face.

The skull or cranium is formed of eight plates of bone, firmly joined together at their edges, so as to make an oval box to lodge and protect the brain. There is a round hole in the base of this bony box, through which the spinal cord passes into the canal provided for it, and on either side of this aperture is a smooth bony projection, by which the skull rocks on the topmost vertebra of the spinal column. These projections are termed condyles.

Turning next to the face, we find that it consists of no less than fourteen distinct bones, all of them, except one—the lower jaw—firmly and immovably fixed to each other and the bones of the skull. These fourteen bones provide five large cavities for lodging and protecting the sense organs of sight, smell, and taste.

So far, the structure of man and of all mammals is on similar lines. But man stands immeasurably above any of these creatures. "Endowed with an intellect capable of indefinite improvement, he exhibits but little of that instinct which guides the operations of the lower animals. His knowledge is the result of observation, and is matured by thought; his power of speech and the capability of writing are faculties entirely his own, whereby he can communicate his ideas and transmit to posterity the results of his experience. By no means highly gifted as relates to his bodily strength, his swiftness is very far inferior to that of most animals of his size. Possessing neither strength of jaw nor canine fangs, he is destitute of offensive weapons, and his body being not even clothed with hair, few creatures are, in this respect, left so utterly defenseless, nay, in addition to these disadvantages, he is, of all animals, the longest in acquiring even that strength which is necessary for the supply of his simplest wants, and yet this very feebleness is to him an advantage, compelling him to have recourse to that intelligence with which he has been so highly endowed. Absolutely dependent upon parental care for his support, he must necessarily derive from that source the education of his intellect, as well as of his physical powers, and hence is established an attachment as durable as it is sacred. The very length of his pupilage necessarily gives birth to habits of family subordination, which ultimately lay the foundation of all social order, and tend to multiply indefinitely the advantages derivable from that mutual co-operation, whereby he has succeeded in subjecting or in repelling the attacks of inferior animals—in clothing himself so as to defy the inclemencies even of the most rigorous climate, and in spreading his race over the surface of the earth.

Nevertheless, in reviewing the grand scene of nature, the supremacy of the human race seems to be manifested in nothing more strikingly than in the privilege conferred upon mankind of studying the Creator's works, and learning the great lessons they are so well calculated to teach. Of all the countless creatures that now throng the busy scene of life, or that successively have faded from existence, not one has been permitted to inquire from whom or whence it received its being. Man alone has been taught to recognize his Maker's hand, which formed all living things, each in its separate sphere, and still upholds and guides the wondrous system He Himself created."

So then it is man's intellectual power which raises him to this lofty height, utterly unapproachable by the rest of God's creatures. In man the brain-case is developed; in the lower animals, on the contrary, the development is in the direction of the face, and not of the skull. The face is always disproportionately large as compared with the skull.

That this is no mere chance accident may be readily seen by comparing the heads of a man, a gorilla, and a horse. If a tape were passed round a person's head, so as to cross the eyebrows and both ears, and the two ends were then tied at the nape of the neck, it would show roughly the proportion between skull and face, and give some idea of the enormous brain capacity in man.

Turn from this to examine the heads of any of the lower animals, and the contrast is at once sharp and striking. Even in the great apes, and they make the nearest approach to man, it is the head, quite as much as the hand, that stamps them as a distinct creation.

Let us try to find the reason for this special development. The face is designed mainly as a lodgment for the sense organs of sight, smell, and taste. These sense organs mean to the brute creation the main part of their existence. The keenness of sight, smell, and also of hearing is as necessary to the hunted as to the hunting animal—in the one case to give the signal of danger, in the other to guide the hungry prowler to its prey. What then is more natural than that these sense organs and of course their bony lodgments should be developed at the expense of the rest of the head? Length of face, for instance, means a corresponding development of the nasal cavities, with greatly increased capacity for the spread of the nerves of smell. In every animal that depends upon its sense of smell either for its safety or its food, we find an elongated face.

Then next as regards the mouth. Feeding being the chief business of these creatures' lives, it is quite natural to look for a special development of the organ of taste to guide them in the choice of their food, and of the jaws and teeth to masticate it.

Moreover, with many of them, the mouth, jaws, and teeth are not merely feeding organs, but weapons of attack and defense. In either case the animal depends upon them for its very existence. The brain, such as it is, has no other duty than to act as overseer to these special organs; here we have in a nutshell the reason why there is special development of the face at the expense of the skull or brain-case.

Just one other thought, and that was the only reason for mentioning the condyles at the base of the skull. Man walks erect. He is the only one of God's creatures to whom this attitude is natural. Is this an accident? Let us see. The head rocks to and fro on these condyles, which fit into corresponding hollows in the top of the Atlas vertebra. In no other animal do we find these condyles placed so far forward as in man. If we examine the various types of animals from man downwards, we find the condyles nearer and nearer to the back of the skull. The consequence is that the weight of the head does not rest directly on the spine, as it does in man, but upon the muscles and ligaments which bind the two together.