. Quain's elements of anatomy . cles are the mostcomplex examples: the complexity having been produced in the latter by the multi-plication of the tunics. In conformity with this view it may be mentioned thatPacinian corpuscles are frequently found, especially in the lower animals, in whichthe tunics are few in number and the corpuscles correspondingly smaller. On theother hand, the round end-bulbs approach more nearly some of the tactile cor-puscles in structure, those, namely, of a, simple kind, such as are met within birds, which form a transition to the much more complicated tactile corpus
. Quain's elements of anatomy . cles are the mostcomplex examples: the complexity having been produced in the latter by the multi-plication of the tunics. In conformity with this view it may be mentioned thatPacinian corpuscles are frequently found, especially in the lower animals, in whichthe tunics are few in number and the corpuscles correspondingly smaller. On theother hand, the round end-bulbs approach more nearly some of the tactile cor-puscles in structure, those, namely, of a, simple kind, such as are met within birds, which form a transition to the much more complicated tactile corpuscleswhich occur in mammals, and especially those in the papillfB of the humanhand. At the same time it cannot be supposed that there is any fundamentaldifference in the two kinds of end-bulb, although the aiTangement of the END-BULBS. 171 cells in the core and the course taken by the nerv^e-fibre is seemingly different,since we see that in different animals those of the one kind are replaced bythose of the other kind. Fig. Fig. 171.—End-bulbs from the husian conjukctiya. (Longworth.) A, Eamification of nerve-fibres in the mucous membrane, and their termination inend-bulbs, as seen-with a lens; B, an end-bulb more highly magnified; a, nucleated capsule ;b, core, the outlines of its component cells are not seen; c, entering fibre branching and itstwo divisions passing to terminate in the core at d; C, an end-bulb treated with osmicacid, showing the cells of the core better than B; a, the entering nerve-fibre; b, capsulewith nuclei; c, c, portions of the nerve-fibre within the end-bulb, the ending of thefibre is not seen ; d, e, cells of the core. On account of the light which they throw upon the structure of the end-organsof mammals, a short description of the tactile end-organs of birds may not beout of place here. Tactile corpuscles of l)ircls.—It was noticed by Grandry that in the soft skincovering the bill of certain birds, such as the duck and goose, a peculiar for
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Keywords: ., boo, bookcentury1800, booksubjectanatomy, booksubjecthumananatomy
