. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. 196 COMPARATIVE ANATOMY. in the skin of Birds and Mammals, and in the former they are particularly abundant on the beak and at the bases of the con- tour-feathers of the wings and tail, and are also found on the tongue. They occur, moreover, in various other regions, both in Birds and Mammals { the various organs of the abdominal cavity, the con- junctiva, the fasciiB, tendons, liga- ments, vas deferens, periosteum, peri- cardium, pleura, corpus cavernosum and spongiosum, the wing-membrane of Bats, &c.). The ta
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. 196 COMPARATIVE ANATOMY. in the skin of Birds and Mammals, and in the former they are particularly abundant on the beak and at the bases of the con- tour-feathers of the wings and tail, and are also found on the tongue. They occur, moreover, in various other regions, both in Birds and Mammals { the various organs of the abdominal cavity, the con- junctiva, the fasciiB, tendons, liga- ments, vas deferens, periosteum, peri- cardium, pleura, corpus cavernosum and spongiosum, the wing-membrane of Bats, &c.). The tactile cells and tactile and club-shaped corpuscles are all con- cerned with the sense of touch. It is impossible to say definitely what nerve-endings have to do with the perception of temperature; it is not improbable that the touch cells, as well as the nerve-fibres often pro- vided with varicose swellings which end freely in the epidermis, are con- cerned in this process. Such free nerve-endings occur in the skin of all Vertebrates, and consist of an intercellular network, no direct con- nection between nerve and epithelial cell having been observed. Pig. 155. -A Pacinian PtJSCLE. COE- A, axis fibre; A^, tufted or knob- like end of the same ; NS, nuc- leated sheath of nerve, which passes into the external longi- tudinal series of lamellfe, L; Q, internal, circular layer of the external part of the club ; JK, internal part of the club formed of the cell-pillars. OLFACTOEY ORGAN. The olfactory lobe as already mentioned (p. 153) represents a pro- longation of the secondary fore-brain, the ventricle of which is tem- porarily or permanently continued into it. In some cases it becomes differentiated into olfactory bulb, tract, and tubercle (pp. 159-17-5). The olfactory nerves proper are connected with the bulb, and are usually arranged in a single bundle on either side, with more or less distinct indications of a subdivision into two bundles: they ap- parently arise in continuity w
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