ORGANS OF THE BODY. 



COS 



9. Sensory Apparatus. 



301. 



The skin in man (fig. 565), the organ presiding over the sense of touch, 

 consists of the cutis vera (below, c), the cuticle (a, b), the subcutaneous 

 areolar tissue (h), nerves (&), vessels (d), sudorific (#, e, f), and sebaceous 

 glands, hairs and nails. 



All these parts have been already separately considered in speaking of 

 the several tissues. For the cutis, see p. 228; the epidermis, p. 144; 

 the subcutaneous areolar tissue, and the collection of fat cells occurring in 

 it, 120-123. The nerves, as far as their course and mode of termina- 

 tion is known, were discussed in 185 and 187. The two species of 

 glands occurring in the skin have been already spoken of generally, at 

 198 and 196, in describing glandular tissue. Hair has been dealt with 

 in 212, and the nails in 99. 



The thickness of the cutis varies in different parts of the body, ranging 

 from 0*45 to 3*38 mm. It is thinnest in the eyelids, the glans penis and 

 prepuce, and inner surface of the labia majora. In the face, the scrotum, 

 and areola of nipple it becomes thicker, varying from 0'68 to 1*13 mm., 

 and on the forehead it is 1 '50 mm. Its average depth, on most parts of 

 the surface of the body lies between 1*69 and 2*26 mm. On the sole of 

 the foot, the nates and back, and often, likewise, in the palm of the hand, 

 it attains the greatest thickness. In males it is stronger than in females, 

 and in children under seven 

 years of age it is hardly half 

 as deep as in the adult (C. 

 Krause). 



The epidermis also, already 

 considered at greater length in 

 another place, varies much in 

 different localities, and, more- 

 over, in a much higher degree 

 than the corium. This varia- 

 tion affects principally its cor- 

 neous layers ; while the soft 

 strata of cells underneath only 

 range from 0-1128 to 0-0347 

 mm. or so ; the horny portion 

 may vary from 0*0347 to 2 -26 

 mm. Its average thickness, in 

 most regions, was fixed by C. 

 Krause at 0-075 1-0 -1735 mm. 

 The epidermis attains the great- 

 est strength in the palm of the 

 hand and sole of the foot, [in 

 both of which situations, as has 

 been known from the earliest 

 days of histology, this inequa- 

 lity may be noticed even in the 

 embryo. 



The tactile papillae of the skin have been already described in 136. 

 They are to be found over the whole extent of the latter, but present con- 



Fig. 565. Vertical section of human skin, a, superficial 

 laminae of the epidermis; 6, rete Malphighii. Below 

 this the corium is seen forming papillae at c, and 

 merging into subcutaneous areolar tissue underneath ; 

 g, sweat glands, and their ducts e and/; d, vessels; ', 

 nerves. 



