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actions and reactions. Under the head of psychic functions are included all operations of the nervous system as well as all functions of like nature which may exist in organisms without specialized nerve fibers or nerve cells. As thus defined mind would include all phenomena of irritability, and even plants have the rudiments of it. The operations of the mind in this sense need not be conscious. With the lower animals almost all of them are automatic and unconscious. With man most of them must be so. All functions of the sensorium, irritability, reflex action, instinct, reason, volition, are alike in essential nature though differing greatly in their degree of specialization.

In another sense the term mind is applied only to conscious reasoning or conscious volition. In this sense it is mainly an attribute of man, the lower animals showing it in but slight degree. The discussion as to whether lower animals have minds turns on the definition of mind, and our answer to it depends on the definition we adopt.

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A "pointer" dog in the act of "pointing," a specialized instinct (Permission of G. O. Shields, publisher of Recreation.)

CHAPTER XXVII

ECONOMIC ZOOLOGY

315. Uses of animals to man.-Economic zoology treats of the value of animals for the purposes of man. These services are enormously varied, and in this chapter we can give only a bare enumeration of some of the most conspicuous lines of service, leaving the student to develop the details. At the outset we may remember that most of the species of animals have inhabited the earth longer than man has, and that we have no right to suppose that the reason for their creation was to render him some service. Thousands and thousands of species can be of no possible use in human affairs, and a few are related to man only through their ability to inflict positive injury. Of harmful nature are the insects with poison glands connected with the mouth, many of those with stings, the snakes with venom fangs, the poisonous Gila monster among lizards, some of the great beasts of prey, and, perhaps most of all, the noxious types of mosquitoes, who transfer to the human body the germs of certain diseases, as malaria, yellow fever, and filariasis. Other noxious animals are the vermin―rats and mice and the like-which infest houses and may carry disease, the many forms of internal and external parasites, intestinal worms, ticks, mites, and the like. Harmful in other ways are the hordes of insects injurious to vegetation; and some mammals, as rabbits and gophers, are at times extremely destructive to valuable plants.

316. Domestic animals.-The very earliest records of man show that he trained those animals about him which

could be made to minister to his needs or his pleasure. The young of almost any species can be rendered friendly and fearless by kind treatment. Naturally those most easily tamed and most useful when reared received the most attention. Of the young born in domestication, those most tractable or most helpful would be most cherished. Thus during the lapse of ages by a process of selection, conscious or unconscious, distinct breeds were formed, many of these differing from the original stock more than distinct species differ from each other. Varying needs brought greater and greater differences among breeds; thus all dogs are domesticated wolves of different species, but the distinctions between St. Bernard dogs, Eskimo dogs, greyhounds, pugs, lap-dogs, and the tiny hairless Pelon dogs of Mexico are far greater than the differences separating different kinds of wolves.

317. Formation of new races.—With the advance of civilization unconscious selection has developed into conscious choice, and new and improved races can be planned and developed with almost absolute certainty of success. Selective breeding has been called "the magician's wand," by which the breeder can summon up new forms useful to man or pleasing to his fancy. In general, new varieties are formed by crossing old ones, each of which has certain desirable traits. These may be combined in certain of the young, or other qualities, new or unforeseen, may appear. These are retained as the basis of the improved race, while those individuals not possessing the desired characters are discarded. By pursuing this method for a certain number of generations the new type may become more or less perfectly established. In this regard almost any desired result is possible with time and patience. Those species most widely domesticated have, in general, developed the greatest number of distinct races or breeds. Among these are the dog, the horse, the donkey, the ox, the sheep, the goat, the hog (descended from the wild boar), the rabbit,

the cat, the fowl, the goose, the duck, the peacock, the guinea-hen, the camel, the honey-bees, the silk-worm, the elephant, the llama, the reindeer, the falcon, the turkey, the ferret, the different parrots, the guinea-pig, and other species. Those forms domesticated for special purposes or within a narrow range are less likely to form varieties.

318. Artificial propagation.-Many animals are bred within regions not formerly occupied by them, although being in no sense domesticated. Among these are the various kinds of salmon and trout, the shad, the striped bass, the carp, goldfish, and many other fishes, the oyster, the Chinese pheasant, the lady-birds. In some cases the eggs are taken and hatched under artificial conditions. This is especially the case with the salmon and trout. In other cases the animals are simply liberated in a new region to make their way in competition with other species.

319. Services of animals.-The chief services rendered by animals may be treated under the following heads:

Food, clothing, ornaments, use in the arts, as destroyers of injurious animals, as servants, and as friends.

320. Animals used as food.-All races of men have fed, in part at least, on the flesh of animals, either raw or cooked. For this purpose certain species have long been domesticated. As a rule, those mammals and birds which are wholly carnivorous have been rejected by man as unfit for food; but this rule does not apply to the class of fishes. Among the animals whose flesh is especially valued may be named the ox, the sheep, the goat tribe, the deer tribe, the hog, and, in general, all hoofed animals with four toes. Besides these, the various rabbits, squirrels, bears, raccoons, opossums, fur seals, the large bats, certain monkeys, some whales, and a variety of other mammals are largely eaten by men on account of the excellence of their flesh. All mammals, excepting the strictly carnivorous cats and wolves, are considered welcome food by some

races of men, and even these have not been wholly rejected.

The milk of the larger hoofed animals-the cow, sheep, goat, buffalo, and even the horse and the ass-has formed an important part in human diet.

All the larger birds which are not strictly carnivorous are eaten by man, and the eggs of these and many others, domestic birds and wild birds, have formed a large part of his diet. In China a certain species of swallow (Collocalia) forms a nest in part from a secretion from its own stomach. This substance forms an agreeable basis for soup, the socalled edible bird's-nest.

Among the reptiles certain species of turtles have flesh of great delicacy-for instance, certain land species, as the Maryland diamond-back terrapin, and some of the great sea-turtles. Among the amphibians, the chief food product is found in the delicate muscles of the legs of various species of frogs.

Of the 12,000 known species of fishes, many are too small to be worth taking. These serve as food for larger fishes. A few dozen species in the tropics have flesh containing a bitter alkaloid, which is more or less poisonous. The great majority are, however, excellent as food, and upward of 5,000 species may be fairly called food-fishes. Certain fishes yield jelly-like substances from the air-bladder or other structures. The eggs of the sturgeon are prepared to be eaten as "caviar." Among the fishes most delicious as food, the eulachon of the Columbia River perhaps ranks first. The ayu, or samlet, of Japan resembles it. Next we may place the pámpano of the Gulf of Mexico, the Spanish mackerel of the same region, the whitefish of the Great Lakes, the bluefish and weakfish of New England, and the various kinds of trout, grayling, bass, shad, and pickerel. The sole, the surmullet, and the turbot rank among the first of the fishes of Europe. Of far greater economic value than any of these, from their exceeding abundance,

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