. A manual of zoology. Zoology. IV. VERTEBRATA: MAMMALIA 545 Class III. Mammalia. The mammals occupy the highest place among the vertebrates, and consequently in the animal kingdom; they also possess a special interest for us, for man, in structure and development, belongs to the group, although separated in intelligence from the most highly organized of the members by a wide gap. The most striking characteristics of the mammals are furnished by the skin. In fact one may, vv'ith Oken, call them hair-animals, since hair is as diagnostic as feathers are for birds. The hairs (fig. 596, H) are cut
. A manual of zoology. Zoology. IV. VERTEBRATA: MAMMALIA 545 Class III. Mammalia. The mammals occupy the highest place among the vertebrates, and consequently in the animal kingdom; they also possess a special interest for us, for man, in structure and development, belongs to the group, although separated in intelligence from the most highly organized of the members by a wide gap. The most striking characteristics of the mammals are furnished by the skin. In fact one may, vv'ith Oken, call them hair-animals, since hair is as diagnostic as feathers are for birds. The hairs (fig. 596, H) are cuticular structures which are seated on papilla; of the corium, and are nourished by blood-vessels in these. The lower end, the root of the hair, lies in a pit in the epidermis, the hair follicle, and is surrounded by a. Fig. 596.—Section of skin of man (from Wiedersheim). Co, corium (derma); D, oil gland; F, fat; G, blood-vessels; GP, vascular papilla; H, hair; A'', nerves; Np, nerve papilla; Sc, stratum comeum; SD, SD', sweat gland and duct; SM, stratum Malpighii. double envelope, the epithelial root sheath, formed by an inpushing of the epidermis and an outer connective-tissue follicular sheath. Small muscles attached to the base of the larger hairs serve for their erection. Since side branches are lacking, the structure of the hair is more simple than that of feathers, and the forms fewer. Wool is characterized by its spiral turns; then there is straight hair which, by increase in size, forms the 'whiskers' {vibrissa:) on the upper lip of many mammals, bristles (swine), and lastly the spines of hedgehogs and porcupines. In the pelts of many animals two kinds of hair may occur, wool below and straight hair outside. Histologically hair consists of cornified cells, often arranged in medullary 35. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not p
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
