. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. TEGUMENTARY ORGANS. 505 appears to me to be clear; for the knob which projects into the cavity of the mucous canal is homologous with the central "nucleus" of the Savian body, and this with the solid axis of the Pacinian body,and with the corpusculiun tactiis, so that the"" tactile " sac of the Chi- niaera, e. g., may be said to be a tactile cor- puscle which is connected with the surface of the integument. No organ at all resembling these has cer- tainly been met with, above the class of Fishes,
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. TEGUMENTARY ORGANS. 505 appears to me to be clear; for the knob which projects into the cavity of the mucous canal is homologous with the central "nucleus" of the Savian body, and this with the solid axis of the Pacinian body,and with the corpusculiun tactiis, so that the"" tactile " sac of the Chi- niaera, e. g., may be said to be a tactile cor- puscle which is connected with the surface of the integument. No organ at all resembling these has cer- tainly been met with, above the class of Fishes, in either Reptilia or Birds, but in Mamma- lia there are structures which must, I think, be placed in the same category. About the lips and nose of almost all mammals in fact, there are certain long, strong hairs, the vi- brissa? or "whiskers" (fig. 321.)- These in their general structure resemble ordinary hairs, but the sac of each, instead of lying free in the enderon, is enclosed in a second thick sac, composed of firm, dense, connective tissue, which attains at times an almost cartilaginous hardness. A looser areolated tissue connects this with the outer surface of the proper hair sac, and supports an abundant .vascular net- work proceeding from vessels which enter at the deep end of the sac. Furthermore, a very considerable nerve pierces one side of the " sclerotic " coat near this end, and passes to the surface of the proper hair sac, upon which it spreads out and forms a nervous expansion, its fibrils dividing and subdividing, and so terminating. Fig. 321. mammal and the fish, I think one cannot but be struck with the similarity of plan between their vibrissre and the " tactile " canals. The sensory impression is conveyed to the gelati- nous contents of the canals in the fish by the vibration of the dense medium in which it lives; while in the mammal the impulse is communicated by the contact of some external object with a long elastic hai
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