EPIDERMIS. 249 



In addition to the papillae, we observe on the surface of 

 the epidermis a great number of lines or furrows which 

 map it out into a network of small polygonal and lozenge- 

 shaped spaces ; these are of two kinds, the one large and 

 coarse and corresponding with the flexures of the joints ; 

 the others smaller, occupying the interspaces between the 

 larger, and also being generally distributed over the surface 

 of the epidermis, where the articular furrows have no ex- 

 istence. The plan of arrangement of the smaller lines is 

 as follows : a number of straight lines, usually from six to 

 ten, radiate, like the rays of a wheel from its centre, from 

 each hair-pore ; these usually come in contact with the lines 

 proceeding from other hairs. These radiating lines thus 

 mark out the surface into triangular spaces, between which 

 are usually situated two or three other pores, those of the 

 sebaceous and sweat glands ; from each of these also similar 

 radiating lines proceed ; these unite with the coarser lines 

 given off from the hair follicle, and occasion a still further 

 subdivision of the surface of the epidermis into triangular 

 spaces. The result of this minute subdivision is to occasion 

 the whole surface of the epidermis to assume a minutely and 

 beautifully reticular appearance. The coarser lines are best 

 seen in the palms of the hands and soles of the feet, while 

 the smaller and finer lines may be readily traced, following 

 the disposition just described on the back of the hand. 



The effect of water in rendering the cells of tesselated 

 epithelium white and opaque has been referred to : its long- 

 continued application to even the living epidermis produces a 

 similar result, which most persons must have observed, al- 

 though some would be at a loss to account for it ; thus, the 

 skin of the fingers of those who have been engaged in wash- 

 ing for some hours becomes of a pearly whiteness. 



It sometimes happens that epidermic cells are developed 

 in increased and abnormal quantities, giving rise to tumours, 

 and which are by no means of uncommon occurrence. 



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