. The chordates. Chordata. 676 Comparative Morphology of Chordates rrPrrr. Fig. 506. The olfactory organ of man. (A) Right nasal cavity, with the nasal septum turned up along its superior border. The olfactory area is indicated in black. (After Read.) (B) Section of the olfactory mucous membrane prepared by the silver technic. The olfactory cells and fibers are in black. (X 550.) (C) Isolated elements of the olfactory epithelium. The olfactory cells bear fine "hairs" re- sembling cilia. (X 735.) (After Brunn.) (Courtesy, Jackson: "Morris' Human Anatomy," Philadelphia, The B
. The chordates. Chordata. 676 Comparative Morphology of Chordates rrPrrr. Fig. 506. The olfactory organ of man. (A) Right nasal cavity, with the nasal septum turned up along its superior border. The olfactory area is indicated in black. (After Read.) (B) Section of the olfactory mucous membrane prepared by the silver technic. The olfactory cells and fibers are in black. (X 550.) (C) Isolated elements of the olfactory epithelium. The olfactory cells bear fine "hairs" re- sembling cilia. (X 735.) (After Brunn.) (Courtesy, Jackson: "Morris' Human Anatomy," Philadelphia, The Blakiston Company.) turbinate are relatively narrow and convex upward, but are not rolled into actual "; Of the three adult turbinals, usually only the upper of the two ethmoturbinals is olfactory and only a part of its surface is occupied by olfactory cells. Also, the adjacent upper region of the nasal septum is olfactory. The total olfactory area for the two human nasal cavities has been estimated at from 5 to 12 square centi- meters, which is a small part of the nasal surface. The higher estimates are probably more nearly correct. The human olfactory surfaces are so restricted to the posterodorsal region of the nasal cavity that they are out of the main part of the respiratory current. During ordinary easy breathing, the presence of an odorous substance in the air may not be noticed, but a forcible snuffing, drawing more air up into the olfactory region, may reveal it. Dogs and other mammals may be observed now and then snuffing in air. The turbinals are important quite aside from their olfactory func- tion. They are an "air-conditioning" apparatus. Their investing mem- branes are highly vascular. Hence the surfaces are warm. Glands keep them covered by a layer of moisture. On its way through the nasal labyrinth, the inhaled air (if cool) is warmed and moistened, thus becoming adapted to reception by the lungs. Also, the mucus-covered surfaces serv
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