Comparative anatomy of vertebrates

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1886 edition. Excerpt: ...confined to the mouth-cavity (tongue) 1 Similar structures arc also present in Crocodiles, and in the skin of the back of Trionyx cellular bodies exist, which most probably are to be regarded as tactile organs. and to the beak (cere), and lie much more closely together, forming definite masses, or "tactile corpuscles." Each of these is surrounded by a nucleated connective-tissue investment, from which septa extend into the interior, partially separating the individual tactile cells from one another. Fio. 138.--A Tactile Corpuscle (end-bulb) From The Conjunctiva Of A Mammal. A", nerve (the neurilemma of which at t becomes continuous with the investment of the tactile corpuscle; A', K, nuclei in the investment; N, the coiled termination of the nerve (axis-fibre) passing to the tactile cells T, T). Fio. 139.--A Pacinian Corpuscle From The Beak Of The Duck. (After J. Carriere.) ZZ, cells of the nerve-sheath; L, longitudinal, and Q, circular layers of the investing lamella;; JK, central knob, with the two pillars of cells; A, axis-fibre, with protoplasmic investment, entering the corpuscle at A1; MS, medullary sheath; Nl, neurilemma, which becomes continuous with the investment of the corpuscle at t, t In Mammals the tactile cells are either isolated, as, for instance, on the hairless portions of the body, or they give rise to oval coipuscles, each consisting of a many-layered and nucleated investment, into which a nerve passes, becomes twisted up, and ends in one or more terminal ganglion cells (Fig. 138). From the Rcptilia onwards, so-called Pacinian corpuscles are present in addition to the above-described tactile organs. They undergo very numerous modifications, but each consists essentially of numerous concentric lamellae...