The microscope and its revelations . haii-s on a larger scale;for the quill is the part contained within the follicle,answering to the bulb of the hair; and whilst the outerpart of this is converted into the peculiarly-soKd horny sub-stance forming the barrel of the quill, its interior isoccupied, during the whole period of the growth of the feather,with the soft pulp, only the shrivelled remains of which, how-ever, are found within it after the quill has ceased to grow. 411. Although the Hairs of different Mammals differgreatly in the appearances they present, we may generallydistinguish in t
The microscope and its revelations . haii-s on a larger scale;for the quill is the part contained within the follicle,answering to the bulb of the hair; and whilst the outerpart of this is converted into the peculiarly-soKd horny sub-stance forming the barrel of the quill, its interior isoccupied, during the whole period of the growth of the feather,with the soft pulp, only the shrivelled remains of which, how-ever, are found within it after the quill has ceased to grow. 411. Although the Hairs of different Mammals differgreatly in the appearances they present, we may generallydistinguish in them two elementary parts; namely, a corticalor investing substance, of a dense horny texture, and a STRUCTURE OF HAIRS. 699 medullary or pith-like substance, usually of a much softertexture, occupying the interior. The former can sometimesbe distinctly made-out to consist of flattened scales arrangedin an imbricated manner, as in some of the hairs of the Sable(Kg. 308); whilst, in the same hairs, the medullary substance is Fig. Fig. 309 TIS? ^^^^^ ^t W jfC ^ ^ > !w H j^JC^^ -^ fej ^ —5 Lj Y^i)C< ^\^j & Fig. 308. Hair of Sahle, showing large rounded cells in its interior,covered by imbricated scales or flattened cells. Fig. 309. Hair of Musk-deer, consisting almost entirely of poly-gonal cells. Fig. 310. composed of large a b c spheroidal cells. Inthe Musk-deer, onthe other hand, thecortical substanceis nearly undistin-guishable; and al-most the entire hairseems made up ofthin-walled polygo-nal cells (Fig. 309).The hail of i\LQ Rein-deer, though muchlarger, has a verysimilar structure;and its cells, exceptnear the root, areoccupied with airalone, so as toseem black by trans-mitted light, except when penetrated by the fluid in which Small Hair of Squirrel:—b, Large Hair ofSquirrel:—c, Hair of Indian Bat. /v^ 700 TERTEBRATED ANIMALS. they are mounted. In the hair of the Mouse, Squirrel, andother small Rodents (Fig. 310, a, b), the cortical
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