This section is from the book "Human Physiology For The Use Of Elementary Schools", by Charles Alfred Lee. Also available from Amazon: Human Physiology, for the Use of Elementary Schools.
1. Cuvier has divided animals into four great groups. 1. The vertebral. 2. The molluscous. 3. The articulated. 4. The radiated. The three last are destitute of vertebrae, or a connected series of bones to form a spinal column. They are, therefore, called invertebrated, while the term vertebrated is applied to the former. The vertebral are again divided into four classes, viz. 1. Mammalia. 2. Birds. 3. Reptiles. 4. Fishes. These are also distinguished by the terms warm, and cold blooded; the warm blooded, including the two former, which possess a temperature considerably above that in which they live ; while the two latter, or the cold blooded animals, are but little warmer than that of the medium by which they are surrounded. The mammalia are divided into nine orders ; Birds into six; while Reptiles include Tortoises, Lizards, Serpents, and Frogs, Fishes are divided into the Cartilaginous and Bony.
2. Molluscous animals, as the name signifies, are those which have no bones corresponding to those of the higher orders of animals. They include all those animals with soft bodies, which dwell in calcareous habitations, constructed by themselves ; many of them are accordingly called shell fish, such as the oyster, muscle, clam, etc. This division also embraces the snail, slug,, and the nautilus. The articulated class includes such animals as are furnished with joints, with a hard external crust, or skeleton, to which are attached the organs of motion. It embraces the annelides, or red blooded worms, the Crustacea, (the lobster and crab,) Spiders, and Insects. The Radiated class includes the Zoophytes, or Plant animals, so called from their resemblance to the vegetable kingdom. Most of these are of a soft texture, as the Polypus, so well known from its being capable of existing when turned inside out, and of reproducing any part of its body when destroyed by accident. To this class belongs the Sponge, and the numerous families of the Coral.
3. The mammalia are placed at the head of the animal kingdom ; not only because it is the class to which man himself belongs, but because it also enjoys the most numerous faculties, the most delicate sensations, the most varied powers of motion, and the highest degree of intelligence.
4. The peculiar characters of these different classes must be learned from works which treat especially of Comparative Anatomy. It will be proper, however, in this place, to point out some of the peculiarities which distinguish man.
5. In structure and external shape, man bears considerable resemblance to some varieties of the ape tribe, particularly the ourang outang. But we find his position to be upright; his foot is large, and the leg placed vertically upon it; while the toes are short and but slightly flexible, and the great toe is horizontal with the others, so that his feet is well adapted to support the body, but cannot be used for seizing or climbing. Apes have thumbs both upon their hands as well as feet, so that they can seize with both equally well. The head of man is also very large and heavy, owing to the magnitude of the brain, and the smallness of the cavities of the bones ; yet the means of supporting it, except in a perpendicular position are very small, as the ligament of the neck, which in quadrupeds is very thick, in him is almost wanting.
6. Besides this, the spinal column is so constructed, that its flexure forwards is not prevented, so that should he attempt to walk on all fours, his mouth and eyes would be directed towards the earth, and he could not see before him, while in an erect attitude he preserves the use of his hands, and at the same time his organs of sense are most favorably situated for observation.
7. Though man surpasses all other animals in dexterity, yet there are many that exceed him in strength, swiftness, and the acuteness of many of the senses. The eagle excells him in acuteness of vision, the grey hound in delicacy of smell, and a vast number of animals in strength, yet reason makes up for all other deficiences. Though physically defenceless, yet the whole brute creation is subjected to his control.
8. It was formerly supposed that man, because gifted with the highest mental endowments possessed the largest of all brains. But as elephants and whales surpass him in this respect, and the sagacious monkey and dog have smaller brains than the comparatively stupid ass, hog, and ox, the opinion was relinquished, and man was said only to have the largest brain in proportion to the size of his body. But more extensive observation proved that canary and other birds, and some varieties of the monkey tribe, have larger brains than man in proportion to the body, and several mammalia to equal him in this particular ; and as rats and mice too, surpass the dog, horse, and elephant in the comparative bulk of their brains ; this opinion gave way to the one now generally adopted by physiologists, viz. that man possesses the largest brain in comparison with the nerves arising from it.
9. In consequence of the great size of his brain, man has a larger facial angle, which is the space included by lines drawn from the centre of the ear to the root of the nose, and from thence to the forehead. In the best formed human heads, this angle is equal to 80 or 90 degrees. In man also, the chin is more prominent, and the lower front teeth more perpendicular ; his teeth also are of the same length, which is not the case in the inferior animals. Man only can adapt himself to the great varieties of climate, and of food, which exist on the surface of the earth.
10. Lastly, man is possessed of faculties that enable him to trace effects to their causes, to distinguish between virtue and vice, to reflect upon events that have passed, to anticipate the issues of the future ; and, above all, to raise his mind to the Supreme Intelligence, the cause of causes, to whom all nature owes her existence, and to whom, with more or less clearness of conviction, he feels conscious of responsibility.
How is the animal kingdom divided ? What is meant by vertebrated, and what by invcrtebrated animals ? How are the vertebral divided ? What is understood by a warm blooded animal ? What by a cold blooded ? Into how many orders are the mammalia divided ? Birds ? Reptiles ? What are molluscous animals ? What does the articulated class include ? What the radiated ? What class is placed at the head of the animal kingdom?-and why? What species of animals does man most resemble ? How does he differ from the ape tribe ? Is man excelled in any respect by the inferior animals ? Mention some of the peculiarities of man.