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a. The scarf-skin, showing its laminated texture, and four spirally twisted perspiratory tubes which traverse it. b. The papillary layer of the sensitive skin; three clusters of papillæ are seen. c, d. The corium of the true skin; in its upper part, namely, at c, being close and dense in texture; and in its deeper part, as at d, composed of strands of fibres of considerable size. e, e. Little cushions of fat, which occupy the interstices of the strands of fibres in the deep part of the corium. The fat, or rather oil, of the body is contained in little globular sacs or vesicles, packed together in considerable numbers, as is shown in the figure. f. The network of capillary vessels lying at the base of the papillæ, and supplying the latter with blood, by means of capillary loops, of which several are seen in the figure. g. One of the arteries conveying the blood to the capillary network; two others of the same kind are seen in the figure. h. Two perspiratory glands, with their twisted tubes. Several other glands and tubes are seen in the figure.
FIG. 4. A portion of the sensitive skin forming the bed of the nail, magnified nineteen times. In this situation the sensitive skin is disposed in longitudinal folds.
FIG. 5. One of the longitudinal folds of the bed of the nail, magnified 38 times. a. The depth of the plait, in which the capillary vessels are distributed in the form of loops. b. The horizontal network from which the capillary loops spring. c, e. Arteries supplying the horizontal network. FIG. 6. Vertical section of a portion of finger nail, made transversely to the longitudinal folds, magnified 19 times. a. The nail, which is seen to be laminated in texture, is prolonged by a number of thin plates into the substance of the sensitive skin. b. The portions of sensitive skin included between the horny plates of the nail are the longitudinal folds of fig. 4.
ANATOMY OF THE SEBIPAROUS GLANDS.
FIG. 1. A sebiparous gland from the scalp. The excretory duct is slightly twisted; a, is the gland. All the figures from 1 to 11 are magnified 38
FIG. 2. Another sebiparous gland from the scalp; showing the difference of size.
FIG. 3. A sebiparous gland from the skin of the nose. The gland is double, and communicates with the excretory duct by means of two smaller ducts. If it be imagined that the duct a, b, is filled with concreted oily substance, the form, size, and situation of the so-called "grub" will be understood. The extremity at a will become blackened by the dirt floating in the atmosphere, the rest retaining its natural whiteness.
FIG. 4. Another sebiparous gland from the nose. The excretory duct exhibits a spiral twist, like that of a perspiratory duct.
FIG. 5. Another sebiparous gland from the nose.
The duct is filled with the peculiar animalcules of the sebaceous substance; their heads being directed inwards.
FIG. 6. One of the fine hairs, with its appended sebiparous glands, from the ear. The hair-follicles and sebiferous duct are seen to be combined. FIG. 7. A small hair from the scalp, with its sebiferous glands. The latter form a cluster around the shaft of the hair-follicle.
FIG. 8. A hair with its follicle and appended sebiparous gland, from the earpassage.
FIGS. 9, 10. Sebiparous glands of more complicated structure, from the same situation; connected with hair-follicles.
FIG. 11. A sebiparous gland and duct of larger size than the preceding, from the ear-passage.
FIG. 12. A sebiparous gland from the lower eyelid; magnified 19 times. The lobulated structure is shown.
FIG. 13. A full grown specimen of the animalcule of the sebaceous substance, the steatozoon folliculorum.
FIG. 14. An egg of the same animal.
FIG. 15. The form assumed by the egg, previously to the development of legs and other characters of the perfect animal.
FIG. 16. A young specimen undergoing the process of casting its skin. FIG. 17. A small portion of the epidermal sheath of a perspiratory duct, magnified 310 times. It is seen to be composed of a regular mosaic of nucleated cells, the hexagonal and pentagonal forms of the cells being occasioned by their mutual pressure. The relative thickness of the area of the tube and its walls is also indicated.
FIG. 18. A group of downy hairs, from the compacted oily substance of an oil-tube; they are magnified 19 times. The peculiar shape of these little hairs is shown in the figure; they are rounded at the ends, and very little smaller in this situation than in the shaft. Their worn-out-paint-brushlike roots are also seen.
ANATOMY OF THE HAIR.
FIG. 1. A small portion of the shaft of a human hair, magnified 310 times. The waving lines caused by the free edges of the overlapping scales are scen, as is their projection along the edge of the hair. The reason of a hair feeling rough when pulled, from point to root, between the fingers, will be perceived at once, on examining this figure.
FIG. 2. A small portion of the shaft of a human hair, magnified 310 times, showing the appearance of the fibrous structure. The dark streaks are the seat of colour of the hair, and in proportion to their numbers the hair is lighter or darker in its degree or shade.
FIG. 3. Horizontal sections of hair from the beard, magnified 155 times. In this figure the oval shape of the shaft of the hair is seen, as well as the three portions of a hair, namely, its central pith; the fibrous part surrounding the pith, and constituting the chicf bulk of the hair; and its outer transparent thin layer.
FIG. 4. A hair from the scalp, showing its position in the hair-tube and its mode of implantation at the bottom of the latter. a. The epidermal sheath of the hair-tube. b, c, d. The bulb of the hair, composed of cells in