1284 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS 



of the normal pigment is a not uncommon congenital anomaly producing albinism or leuko- 

 derma. It may affect all the skin structures or it may be partial. 



The skin presents certain elevations and depressions due to the fact that it 

 follows more or less closely the contour of the underlying structures, but in addi- 

 tion to this it possesses certain elevations and depressions peculiarly its own. 

 They are found on the skin in various parts of the body. Some are permanent, 

 others only temporary. Large permanent folds which include all the layers of 

 the skin are seen, as the prepuce of the penis and the pudendal labia. The most 

 marked depression is the umbilical fovea. Other conspicuous folds and furrows 

 are seen in the neighbourhood of the lips and eyelids. Certain other less permanent 

 folds and furrows are produced by the action of the joints, joint-furrows, and of 

 the muscles of expression of the skin, "wrinkles." 



Fig. 



1044. — From a Photograph of the Superficial Furrows on the Back of the Hand. 



(X 1.) 



Other minute folds and furrows which affect only the epidermis and the super- 

 ficial layer of the corium are seen in various places. These are represented by the 

 numerous fine superficial creases, unassociated with elevations, forming rhom- 

 boidal and triangular figures over almost the whole of the surface of the skin 

 (figs. 1042, 1043). They are especially numerous on the dorsal surface of the 

 hands (fig. 1044). The fine curvilinear ridges [cristse cutis] with intervening 

 furrows [sulci cutis] arranged in parallel lines in groups on the flexor surface of 

 the hands and feet are also of this type. They form patterns characteristic for 

 each individual and permanent throughout life. 



Fig. 1045. — From a Photograph of the Skin Ridges and Papill.e of the Palm of the 

 Hand. Epithelium Completely Removed Above; Partly Removed Below. (X 5.) 



Papillae corii -< 



Cristae cutis 



— Corpus papillare corii 



~'^3' Sulci cutis 



Among the i)r()joctions arc the large permanent folds of skin such as the labia pudendi, the 

 preputium penis, tlm frenula preputii, clitoridis, and labiorum pudendi, and less marked ridges 

 a.s tlic in(!dian raphe of llie pcriiuMini, scrotuni and penis, and tlie tuberculum labii superioris. 

 Of a somewhat different sort are the touch pads |toruli tactih's| of i\\c liands and feet. Among 

 the larger deincssions in a(hlit ion to t he umbilical fovea, is I he coccygeal foveola, and a consider- 

 able number of wcdl-niarkful jx-rnianent furrows found in various i)laces, such as the nasolabial 

 arid mentolabial sulci, IIk; philtrum labii superioris, the infraorbital sulcus, and the infra- and 

 supraorbitial palpebral sulci, 'riuiro an; nuin("ro>is articular furrows on i)oth the flexor and 

 exten.sor surfaces jiroduf^ed by the action of the joints, and associated with interveiung folds 

 of skin, parti(;ularly on the dorsal s(n-face. They are especially noticeable on the hands. Varia- 

 tions of the palmar joint sulci are due to variations in opposition of the tlnimb and the use of 

 the fingers and the relative arrangement of the thumb and fingers and joints. They are of 



