CHAP. XVII.] THE HAIES. 193 



cells, and fits over a vascular papilla which projects into the 

 bottom of the follicle. The hair grows from the bottom of 

 the follicle by multiplication of the soft cells which cover the 

 papilla, these cells becoming elongated to form the fibres of the 

 fibrous portion, and otherwise modified to form the medulla and 

 cuticle. New hairs are produced indefinitely, so long as the 

 papillae and soft cells remain intact. 



The follicles containing the hairs are narrow pits formed by 

 the involutions of the true skin and the epidermis. They slant 

 obliquely upwards, so that the 

 hairs they contain lie down on 

 the surface of the body. Con- 

 nected with each follicle are 

 small muscles of plain muscular 

 tissue which pass from the sur- 

 face of the true skin, on the side 

 to which the hair slopes, obliquely 

 downwards, to be attached to FlG - H3. SECTION OF THE SKIN 



, , - , , _ SHOWING THE HAIRS AND SEBACEOUS 



the bottom Ot the lollicle. When GLANDS, a, the epidermis; 6, corium; 



these muscles Contract, as thev C> muscles attached to hair-follicles and 



J to under surface of epidermis. 



will under the influence of cold 



or terror, the little hairs are pulled up straight, and stand " on 

 end " ; the follicle also is dragged upwards so as to cause a 

 prominence on the surface of the skin, whilst the cutis vera, 

 from which the little muscle arises, is correspondingly depressed: 

 in this way the roughened condition of the skin known as 

 " goose-skin " is produced. Hairs grow on an average at the 

 rate of half an inch per month. They are found all over the 

 body, except on the palms of the hands and the soles of the 

 feet, and on the last joints of the fingers and toes. 



The sebaceous glands. The sebaceous glands are small saccu- 

 lar glands, the ducts of which open into the hair-follicles. They 

 are lined with epithelium, and secrete a fatty, oily substance 

 (sebum) which they discharge into the hair-follicles. Several 

 sebaceous glands may open into the same follicle, and their size 

 is not regulated by the length of the hair. Thus, some of the 

 largest are found on the nostrils and other parts of the face, 

 where they often become enlarged with pent-up secretion. The 

 sebum lubricates the hairs and renders them glossy; it also 

 exudes, more or less, over the whole surface of the skin, and 



