Other plants are almost equally interesting. Flowers have long been chosen to express the language of sentiment. Even the lowest forms of vegetable life, like the algæ, the mosses and lichens, arrange their parts with symmetry and beauty. Even the microscopic diatoms[8] are exquisite in the perfection of their curves and markings. ANIMAL MECHANISM. Comparative anatomy long since showed us that there is great harmony in the construction of animals. A few principles seem to govern in all. For example: None violate the law of gravity with regard to the line of direction’s falling within the base. They employ the lever, the inclined plane, the pulley, and the mechanical means of applying power, precisely as we do in machinery. The heart is a pump; the stomach is a churn; the backbone has springs; the elbow is a hinge; the muscles are ropes; the nerves are telegraph wires; the ear is a harp, the eye is a telescope. The most perfect mechanism characterizes the construction of all the animal kingdom, but one can do little more than suggest the interest of this most fascinating subject. [Illustration: SHOWING PRINCIPLE OF VENTURI. _Ex._—S V is the sub-clavian vein; J is the jugular vein; D is the thoracic duct, through which the chyle is poured into the blood.] THE TRADES AMONG ANIMALS. An ancient saying declares that “Poets are born, not made,” and classic story informs us that Minerva sprang full armed from the head of Jove. Something like this natural perfection appears in the occupations of the lower orders of creation. Man is a creature of education, absolutely unlimited in point of time in the possibilities of his development. Other animals, within their own limited scope often attain an excellence superior to his. Note the scent of the greyhound, the hearing of the cat, the sight of the eagle. As artisans they have few apprentices, though it must be confessed that some are better workmen than others, and they are not without “bosses.” Observe a few of their trades. The brant-goose is a navigator, which may have already found the pole. The heron is a fisherman, who carries his torch upon his breast. Swallows are excellent masons; so are wasps and the caddis fly.