| OCR Text |
Show 150 DR. F. P. MORENO AND MR. A. S. WOODWARD ON [Feb. 21, and all are remarkably tough. Examined under the microscope, their cuticle is observed to be quite smooth, while the much-elongated cells of the cortex are readily distinguishable. Mr. E. H. Burne has kindly made some transverse sections, which prove the hairs to be almost or quite cylindrical, and none of the specimens examined present any trace of a medulla. The dermal ossicles are very irregular in arrangement, but are to be observed in every part of the specimen, even in the comparatively thin region near the supposed ear. They form everywhere a very compact armour, and some of them are quite closely pressed together ; rarely, indeed, there is a shallow groove crossing a specimen, possibly indicating two components which were originally separate. As shown by every part of the cut margin, and especially Avell in a small section prepared by Prof. Charles Stewart (PI. X V . fig. 1), they are all confined to the lower half of the dermis, neA'er encroaching upon the upper portion in which the hair is implanted. It is also to be observed that where the inner surface of the skin is intact (e. g. around G in PI. XIV.), the ossicles are completely embedded and only faintly visible through the dry tissue. The exposure of a considerable number of them, as already mentioned, is dne to the rupture and partial abrasion of this surface. No tendency to arrangement in parallel lines or bands can be detected ; and large and small ossicles seem to be indiscriminately mingled, although of course allowance must be made, in examining sections and the abraded inner view of the skin, for differences in the plane of adjoining sections and varying degrees of exposure by the removal of the soft tissue. The largest ossicles are oblong in shape when viewed from within, and measure approximately 0-015 m. by 0-010 m.; but the majority are much smaller than these. They are very variable and irregular in form ; but their inner face is generally convex, sometimes almost pyramidal, while the outer face of the few Avhich have been examined is slightly convex, more or less flattened, without any trace of regular markings (PI. X V . figs. 2, 3). In microscopical structure the dermal ossicles are of much interest, and I have examined both horizontal and vertical sections, one of the former kindly prepared by Prof. Charles Stewart. A portion of a horizontal section is shown enlarged about 40 times in PI. X V . fig. 7 ; and one of the Haversian systems from its middle area is represented, much more highly magnified, in fig. 7 a. The tissue is traversed in all directions by a dense mass of interlacing bundles of connective-tissue fibres, Avhich exhibit an entirely irregular disposition, except quite at the periphery of the ossicle. Here they are less dense and are arranged in such a manner as to form at least one darkened zone concentric Avith the margin in the comparatively translucent border. Occasionally, but not at all points, the fibres in this peripheral area may be observed to radiate regularly outwards. Numerous small vascular canals, frequently branching, are cut in A'arious directions ; and the bony tissue, which is developed in every part of the ossicle, exhibits abundant |
