HAIR. 543 



The ducts are slightly curved as they pass through the corium. 

 Where the scarf skin is thick, they assume a spiral appearance ; 

 where it is thin, they open directly out. They consist of two 

 coats ; an outer, continuous with the coriura, and an inner 

 epithelial one, which is continued to the surface. Each sweat- 

 gland is supplied with a cluster of capillary blood-vessels. Their 

 size varies, being very large where perspiration is excessive. The 

 contents of the smaller glands are quite fluid, those of the larger 

 contain fine granules. 



The skin of the horse is characterised by its great sensitiveness, 

 which is still further promoted by the operation of grooming, and 

 artificial protection ; and also by the development and activity of 

 the sudoriferous apparatus ; few animals, if any, perspire so freely 

 as the horse. The large quantity of pigment found in the skin 

 is believed to serve as a protection against the heat of the sun. 

 An epithelial excrescence appears on the distal part of the fore- 

 arm internally, and on the proximal portion of the metatarsus 

 also internally ; these objects, ergots or chesnuts, the "chataignes" 

 of French authors, according to Chauveau, "represent the vestige 

 of the thumb." 



HAIR. 



Hair is an appendage of the skin, and in most mammals forms 

 its external covering. It is a special modification of epidermis, 

 having in its bulk the same essential structure. A hair consists 

 of a root, a shaft, and a point. The root has a bulbous enlarge- 

 ment at its extremity, is lighter and softer than the shaft, and is 

 lodged in a recess or hair follicle, which may either be in the 

 corium or subcutaneous areolar tissue. 



The follicle is dilated at the bottom, to correspond to the 

 root bulb, and the ducts of one or more sebaceous glands open 

 into it. It consists of two coats; an outer or dermic, an inner 

 or cuticular. The outer, composed of areolar tissue, is highly 

 vascular, continuous with the corium, and possesses numerous 

 minute nerve fibrils ; the inner, continuous with the cuticle, is 

 attached at the base of the follicle to the root of the hair. The 

 lining adheres to a hair when plucked out, forming the root 

 sheath. At the bottom of each follicle is a conical vascular 

 papilla, similar in every respect to those on the surface of the 

 skin. This papilla fits into a corresponding depression in the 

 root of the hair. 



