80 GENERAL ANATOMY. 



the eyelids, scrotum, and penis, it is exceedingly thin and delicate. The skin 

 generally is thicker in the male than in the female. 



The areolae are occupied by adipose tissue, hair-follicles, and the sudoriferous 

 and sebaceous glands ; they are the channels by which the vessels arid nerves 

 are distributed to the more superficial strata of the corium, and to the papillary 

 layer. 



Unstriped muscular fibres are found in the superficial layers of ihe corium, 

 wherever hairs are found ; and in the subcutaneous areolar tissue of the scro- 

 tum, penis, perineum, and areolae of the nipple. In the latter situations the 

 fibres are arranged in bands, closely reticulated, and disposed in superimposed 

 laminae. 



The papillary layer is situated upon the free surface of the corium : it con- 

 sists of numerous small, highly sensitive, and vascular eminences, the papillae, 

 which rise perpendicularly from its surface, and form the essential element of 

 the organ of touch. The papillae are conical-shaped eminences, having a round 

 or blunted extremity, occasionally divided into two or more parts, and con- 

 nected by their base with the free surface of the corium. Their average length 

 is about ytftfth of an inch, and they measure at their base about . 3 n th of an 

 inch in diameter. On the general surface of the body, more especially in those 

 parts which are endowed with slight sensibility, they are few in number, short, 

 exceedingly minute, and irregularly scattered over the surface; but in other 

 situations, as upon the palmar surface of the hands and fingers, upon the plan- 

 tar surface of the feet and toes, and around the nipple, they are long, of large 

 size, closely aggregated together, and arranged in parallel curved lines, forming 

 the elevated ridges seen on the free surface of the epidermis. In these ridges, 

 the larger papillae are arranged in a double row, with smaller papillae between 

 them ; and these rows are subdivided into small square-shaped masses by short 

 transverse furrows, regularly disposed, in the centre of each of which is the 

 minute orifice of the duct of a sweat-gland. No papillae exist in the grooves 

 between the ridges. In structure, the papillae resemble the superficial layer of 

 the cutis; consisting of a homogeneous tissue, faintly fibrillated, and contain- 

 ing a few fine elastic fibres. The smaller papillae contain a single capillary 

 loop : but in the larger the vessels are convoluted to a greater or less degree ; 

 each papilla also contains one or more nerve-fibres, but the mode in which 

 these terminate is uncertain. In those parts in which the sense of touch is 

 highly developed, as in the lips and palm of the hand, the nerve-fibres are con- 

 nected with the "tactile corpuscles." Kolliker considers that the central part 

 of the papillae generally consists of a connective tissue more homogeneous than 

 that of the outer part, surrounded by a sort of sheath of elastic fibres, and he 

 believes that these corpuscles are merely a variety of this structure. The cor 

 puscles, and their connection with the nerves, have been described above. 



The epidermis, or cuticle (searfskin), is an epithelial structure, accuratel 

 moulded on the papillary layer of the derma. It forms a defensive coverin 

 to the surface of the true skin, and limits the evaporation of watery vapor from 

 its free surface. It varies in thickness in different parts. Where it is exposed 

 to pressure and the influence of the atmosphere, as upon the palms of the hands 

 and soles of the feet, it is thick, hard, and horny in texture; whilst that which 

 lies in contact with the rest of the body, is soft and cellular in structure. The 

 deeper and softer layers have been called the rete imicnsum, the term irle being 

 used from the deepest layers presenting, when isolated, numerous depressions, 

 or complete apertures, which have been occupied by the projecting papilla'. 



The free surface of the epidermis is marked by a network of linear furrows 

 of variable size, marking out the surface into a number of spaces of polygonal 

 or lozenge-shaped form. Some of these furrows are large, as opposite the flex- 

 ures of the joints, and correspond to the folds in the derma produced by their 

 movements. In other situations, as upon the back of the hand, they are ex- 

 ceedingly fine, and intersect one another at various angles: upon the palmar 



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