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Show j. , a WHY WE BEHAVE j LIKE HUMAN BEINGS By GEORGE DOBJEY, Ph. D LL. D. t Some People Are Born With Gills WB NO longer telr friends from enemies by smell; but we often pick them by tbe shaps of their nose. Man's noes Is not so striking as the elephant's, or even tht ' long-nosed monkey's, but It features bis face ami Is one of his most humnn and super-fluous super-fluous elements. As It U a new acquisition. acqui-sition. It began with mammals. It an- ul llVH a w.aM -- pears lots In fetal. life and develops fully only after birth. Its share and size are hereditary and srs distinguishing distin-guishing traits of race. But It has no more to do with brain power thnn tbe handkerchief that wlprs It As the olfactory nerves slone are connected with tbe hemispheres ot the human brain. It Is Inferred thut ths brain Itself arose In connection with the sense ot smell ; lbs orlglnul brain was a smelling organ. In mammals generally, ths smell sense Is the most highly developed of sll senses. In monkeys. It has already begun to diminish. Some mammals have five pairs of ridges supporting the olfactory organs; soros hoofed animals an-imals have eight; apes usually have three. Mao has from two to five pairs. Tbe nose In the human embryo Is at first a pair of pits or pockets In the skin tbe condition in fishes. The external ex-ternal nose appears much later. The ear also begins ss s pocket. In the first gill-cleft This sinks Into tbe bead until Its outer opening Is closed by the tynpanum or eardrum. A rare anomaly Is sn Individual with two, or even three, external ear openings; open-ings; these represent the second and third gill-clefts. In some fishes the opening remains; their ear Is primarily pri-marily a balancing organ. Our equilibrium equilib-rium sense organ is also located In the Inner ear; If our semilunar canals are -destroyed, we cannot balance ourselves. our-selves. We turn our head toward sounds or cup our hands behind our ears; our ancestors turned their ears. Our eyes are compound and are made up of the same three parts that are found In fishes' eyes. First, s cluster of skin cells dig In to form the lens; skin grows over this, becomes be-comes transparent, and forms tbe cornea. Next, a growth from the neural neu-ral tube reaches out and ends In a cop around the lens. This cup becomes be-comes the retina ; the stalk which Joins cup with tube, the optic nerve. Cells from the middle germ layer now enter the cup snd form the transparent transpar-ent matter of the eyeball. The middle mid-dle layer also supplies skin structure; It Is subject to the horny change of old age. Hence "cataract" of the eye ; the lens has become covered with s scale. - Tbe Asiatic's eye is not oblique. The "slit" appearance Is due to the low nasal bridge supporting the upper lid ; the lid thus folds and appears "Mon. gollan." This "oblique" eye Is not uncommon un-common In white children at birth; when the bridge develops elowly it may persist for pionths, even Into adult life. The tears which wash our eyes-otherwise eyes-otherwise as dirty as our faces come from lachrymal glands In the upper outer corner of each eye. Some have additional tear glands at the sides of the eyes, as have reptiles. Our skin Is a double structure. The outside, or epidermis, Is ectoderm ; the Inside, or dermis, Is derived from the mesoderm. The fetal skin at first Is translucent and not unlike that of fishes. During the third month, the. epidermis begins to become horny, as It Is in adult life, it Is significant that if we lose a third of our skin hy fire, acid, boiling liquid, or flaying, we lose our life. Color of skin is nn inherited trait and Is due to grains of brown or yellow-red pigment In the dermis. Entire absence of pigment in skin, hair, and eyes Is a developmental defect and results in albinos. Albinism Is an inherited in-herited trait and Is found In many animals. White blnckhlnls are as common as white black men. Pigment Pig-ment Is probably due to secretion of an endocrine glund.' To form a better grasping surface, the skin of man's, monkeys', and ninny other mammals' hands and feet Is thrown Into minute ridges, especially prominent on the finger tips. ..Those ridges form loops, spirals, and arches. In no two individuals on earth do they make exactly the same pattern. Hence their unique Importance as marks of Identification. At the fourth month, the embryo begins be-gins to show a fine silky hnlr coat or lanugo (down). This begins to be replaced, re-placed, even before birth, hy a second coat of different character. The lanugo may persist as "down" on the face of girls and women, or even all over the body, as on the so-called dog-faced dog-faced people of the menageries. The lanugo prohnhly represents our adult ancestral condition. Rut no satisfactory satisfac-tory theory has yet been advanced to "accoun for the fact that man Is the least hairy of the prlinntes. Hair does not grow on our bodies In haphazard fashion, hut in lines snd sets of three, four, or five, each set being the hairs that grew beneath one scale of our reptilian ancestors. ((9 by Georg A Dorwy.) |