486 



A TEXTBOOK OF PHYSIOLOGY 



water from the surface. The lymph affords material whereby the 

 chemical change into keratin is effected. 



The true skin dermis, or corium consists chiefly of connective 

 tissue. The outermost layer is a dense fibrous tissue, which is thrown 

 into multitudes of papillae or ridges. Corresponding to these are the 

 patterns, seen on the surface of the epidermis, which cover the ridges. 

 The patterns on the finger tips are peculiar to each individual, and 

 afford finger prints for identification. This layer is well supplied 

 with plexuses of capillary vessels, and also contains some of the 

 organs of sensation, such as Meissner's corpuscles, etc. The deepest 

 layer of true skin consists of fatty or adipose tissue. Besides serving 

 as a fat depot, it is of importance in keeping the heat within the 



FIG. 233. MICROSCOPE, Low POWER. SECTION THROUGH THE SKIN. 



A, Horny layer of cells; B, layers of soft growing. cells; C, thick connective-tissue 

 coat ; D, fat layer ; E, sweat-gland and duct ; F, hair ; G, sebaceous gland ; H, papilla 

 of hair; J, small artery; K, muscle of hair; L, capillaries. 



body. Arctic mammals are protected by thick layers of blubber. 

 It also acts as a cushion, and gives softness of contour and beauty 

 of form to the body. In some positions e.g., neck, scrotum 

 plain muscles fibres are found in the corium. Connecting the two 

 layers of the corium is a loose fibrous-tissue layer. 



Hair follicles are found in all parts of the skin of man, except in 

 that of the palms of the hand and of the soles of the feet. They are 

 developed from the Malpighian layer, which grows downwards into 

 the corium. They consist of various layers corresponding to the 

 epidermis and dermis, the hairs growing up from a layer of cells known 

 as the hair bulb. Smooth muscle fibres, forming the pilo-motor 

 nerves, are attached to each hair follicle, and cause it to stand erect 



