DESCRIPTION OF THE PLATES.

PLATE 1.1

STRUCTURE OF THE SCARF-SKIN.

FIG. 1. A small portion of scarf-skin from the palm of the hand, magnified nineteen times. The parallel arrangement of the ridges, and the manner in which they terminate abruptly every here and there, is shown in this figure; as well as the circular pores of the perspiratory tubes.

a. A vertical section, showing the elevation of the ridges of the preceding. b. Represents the tufts of papillæ of the sensitive skin, which are the cause of the ridges. The spiral coil running up from each tuft is a perspiratory tube.

FIG. 2. The under surface of a portion of scarf-skin from the palm of the hands magnified like the preceding, nineteen times. The ridges and grooves are the reverse of fig. 1. In each of the three grooves represented in this figure are seen numerous oval-shaped depressions for the tufts of papillæ of the sensitive skin, and running along the middle of each groove a slightly elevated line, a, upon which, at short distances, are the conical sheaths of the perspiratory tubes. b. One of the conical sheaths in question. c. A vertical section of the preceding figure. If this be compared with fig. 1, a, the correspondence of the two will be seen. d. One of the

conical sheaths of a perspiratory tube, projecting from the middle of the groove: similar conical sheaths are seen in the other two grooves. FIG. 3. A portion of scarf-skin from the arm-pit, magnified nineteen times. The numerous lines crossing the figure are furrows adapted to the motions of this part of the body. In the compartments between these furrows, smaller divisions are seen corresponding with the little tufts of papillæ of the sensitive layer of the skin. The round spots scattered over the surface are the pores of hair tubes and oil-glands. FIG. 4. A portion of scarf-skin from the back of the thumb, magnified nineteen times. The lines of motion and compartments have a different arrangement from those in the preceding figure, but in nature are the same. The little prominences caused by tufts of papillæ are more strongly marked, and there are several pores of hair-tubes and oil-tubes scattered over the surface.

FIG. 5. A portion of scarf-skin from the back of the hand, viewed upon its under surface, and magnified thirty-eight times. The depressions correspond with the tufts of papillæ of the sensitive skin. This figure illustrates the irregular distribution of the papilla of the sensitive skin, as compared with fig. 2, in which the depressions are arranged in rows.

1 The figures in the first six plates were drawn with the camera lucida; their relative size is consequently preserved.

2

FIG. 6. A thin fragment of scarf-skin, magnified 155 times, showing its construction of flat, polyhedral, overlapping scales, in some of which a nucleus is seen.

FIG. 7. Vertical section of a portion of scarf-skin from the palm of the hand, magnified 155 times. In the lower part of the figure the section has cut across, and then proceeds nearly parallel with, a tortuous perspiratory tube. The cells, of which the scarf-skin is composed, are more open in the lowest than in the upper part of the figure; a nucleus, also, is seen in the cells of the lower stratum, while in the upper the cells are converted into thin scales.

FIG. 8. A series of scarf-skin cells, magnified 310 times, showing the mode of growth of the cells, and their ultimate conversion into scales. These changes take place in the lower stratum of fig. 7.

a. Primitive isolated granules, measuring about ʊʊʊ of an inch in diameter. b. Aggregated granules, composed of several of the preceding, measuring about 100000 of an inch. c. Nucleated granules, measuring about 365 of an inch. d. Cells measuring 300 to ' of an inch. The deepest layer of the scarf-skin is made up of the four preceding elements and has the appearance of a smooth but irregular mosaic. e. Cells measuring of an inch. f. Cells measuring of an inch. g. Cells measuring 10 of an inch. In all the figures from d to g, the cell is composed of a granular centre or nucleus, and of a number of newly-formed young cells, which are arranged around it. h. Two fully-formed cells, measuring of an inch in longest diameter, and converted into flattened scales. These scales have resulted from the growth of the granules and young cells. of g, so that the perfect cell contains cells of secondary formation, and, within some of the latter, smaller cells of tertiary formation; this is a good illustration of a "parent cell."

PLATE 2.

ANATOMY OF THE SENSITIVE SKIN AND NAIL.

FIG. 1. A small portion of sensitive skin, comprehending two ridges, from the palm of the hand, magnified thirty-eight times. Each ridge is composed of two rows of clusters, and each cluster of a number of papillæ. Between rows of papillae, at short distances, are seen the openings of perspiratory tubes. a. One of the ridges. It is this arrangement of papillæ which causes the appearance of the scarf-skin, shown in figs. 1 and 2, plate 1.

FIG. 2. A portion of sensitive skin from the back of the hand, magnified thirty-eight times. The papillæ are seen, singly and in small clusters, scattered irregularly over the surface. The scarf-skin, modelled upon such a surface as this, would have the appearance represented in figs. 3, 4, and 5, plate 1.

FIG. 3. A section of the skin of the palm of the hand, the section being made through the middle of one of the ridges, and not across the ridges, as in plate 1, fig. 1, a. The figure is magnified thirty-eight times.