Volume 1

A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling.

Landois, L. (Leonard), 1837-1902. Lehrbuch der Physiologie des Menschen. English

Date:: 1891

Credit: A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling. Source: Wellcome Collection.

586/602 page 546

$Fig. 359 Papillfe of the skin, epidermis removed, blood- vessels injected ; some contain a Wagner's toucli- corpuscle, a, the others a capillary loop. to 0-1 mm. high) papillae (figs. 356, 358), the largest being upon the volar surface of the hand and foot, on the nipple and glans penis. Most of the papillae contain a looped capillary {g), while in certain regions some of them contain a touch- corpuscle (fig. 359, a). The papillae are disposed in groups, whose arrangement varies in different parts of the body. In the palm of the hand and sole of the foot they occur in rows, which are marked out by the existence of delicate furrows on the surface visible to the naked eye. The chorium consists of a dense network of bundles of white fibrous tissue mixed with a network of elastic fibres, which are more delicate in the papillse. In silversmiths the elastic fibres are blackened by the partial deposition of reduced silver, and the same ob- tains in those who take silver nitrate in such quantity as to produce argyria. The connective-tissue con- tains many connective-tissue corpus- cles and numerous leucocytes. The deeper connective-tissue layers of the chorium gradually pass into the subcutaneous tissue, where they form a trabecular arrangement of bundles, leaving between them elon- gated rhomboidal spaces filled for the most part Avith groups of fat-cells (figs. 356, 358, a, a). [In microscopic sections, after the action of alcohol, the fat- cells not unfrequently contain crystals of margarin (fig. 295).] The long axis of the rhomb corresponds to the greater tension of the skin at that part {C. Langer). In some situations the subcutaneous tissue is devoid of fat [penis, eyelids]. In many situations, the skin is fixed by solid fibrous bands to subjacent structures, as fascia, ligaments or bones (tenacula cutis); in other parts, as over bony promi- nences, bursfe partially lined with endothelium and filled with synovia-hke fluid, occur. Smooth muscular fibres occur in the chorium in certain situations on extensor surfaces {Neumann); nipple, areola mammse, prepuce, perinseum, and in special abundance in the tunica dartos of the scrotum. [Guanin in the Skin.—The skin of many amphibians and reptiles contain brown or black pigment-granules, and other grannies of a white, silvery, or chalky appearance. Lwald and Krukenberg have shown that the latter consist of guanin, and that this substance is very widely diffused in the skin of fishes, amphibians, and reptiles. Test :—Select a piece oi skm from the belly of a frog ; place it in a porcelain capsule as for the murexide test add concen- trated nitric acid, and heat to dryness, when a yellow residue is obtained ; on adding a drop ot caustic soda a red colour is struck. The yellow residue gives no reaction with ammonia, it to the fluid more water be added, and it be then heated, distributed over the surface of the cap- sule, and cooled by blowing upon it, various shades of purple and violet are obtained.] The nails (specific gravity 1T9) consist of numerous layers of solid, horny, homo- geneous, epidermal, or nail-cells, which may be isolated with a solution of caustic alkali, when they swell up and exhibit the remains of an elongated nucleus (fig. 358, ?^, m). The whole under-surface of the nail rests upon the nail-bed; the lateral and posterior edges lie in a deep groove, the nail-groove (fig. 360, e). The chorium under the nail is covered throughout its entire extent by longitudinal rows of ridges (fig. 360, d). Above this there lies, as in the skin, many layers of prickle cells like those in the rete Malpighii (fig. 358, d), and above this again is the substance of the nail (fig. 360, a). [The stratum granulosuni is rudimentary in the nail-bed. The substance of the nail represents the stratum lucidum, there being no stratum corneum {Klein).] The posterior part of the nail-groove and the half moon, brighter part or lunule, form the root of the nail. They are, at the$