THE INTEGUMENTARY APPENDAGES. 799 



prolongation rising up into the hair-bulb. It furnishes the hair with 

 nutrition and the elements of growth. The walls of the follicles of the 

 large hairs, or tentaeula, which garnish the lips of the Horse, or bristle from 

 those of the Cat, are provided with nervous ramifications which endow these 

 appendages with a high degree of sensibility, and enable them to play an 

 important part ia the exercise of touch. 



Two sebaceous glands, and a smooth muscular fasciculus, are annexed to the 

 pilous follicle. The sebaceous glands, which have been already described, 

 open into the sheath of the hair by a small excretory canal, which traverses' 

 the fibrinous walls of the follicle. The muscular fasciculus is situated on 

 the side to which the hair and its follicle are inclined ; it arises from the 

 superficial face of the derma, and terminates at the bottom of the foUicle, 

 which it erects by contracting. When the fasciculi contract over a wide 

 surface, the extent of the skin is diminished, and the hairs are erected and 

 pai'tially ejected from their follicles (producing the cutis anserina). 



(The formation of a hair is identical with the formation of the epidermis 

 by the papillary layer of the derma. The capillary plexus of the follicle 

 throws out plastic lymph which is converted into granules, then into cells 

 which become elongated into fibres. The cells that are to form the surface 

 of the hair, are converted into flat scales that inclose the fibrous structure of 

 the interior. As these are successively produced, they overlap those pre- 

 viously formed, and give rise to the waving lines seen on the circumference 

 of the hair; this overlapping also causes the roughness experienced in 

 drawing a hair between the fingers from its point to the bulb. The latter 

 is the newly-formed part of the hair, its expanded form being due to the 

 greater bulk of the fresh-cells. 



The colour of the hair is very varied in animals, ranging from black to 

 white, red and brown, with all the intervening shades. The tint also 

 changes at difierent periods of life, being sometimes altogether altered 

 between the juvenile and adult periods ; dark-coloured Horses becoming 

 light-coloured as age advances. Besides, it is never uniform in the same 

 animal ; black Horses not unfrequently having white patches and diverse tints, 

 with other dissimilarities. The disease termed " melanosis " is very common 

 in old white Horses which were previously grey, and is supposed to be due 

 to the localization of the black pigment at certain limited points. The hair 

 grows according to the climate, seasons, food, etc., and varies with the species 

 and breed. The coat in every animal is shed at certain times, and is replaced 

 by new hairs. 



The hair preserves the skin from unhealthy external influences — wet 

 and cold for example. It is a bad conductor of heat, and therefore keeps 

 the body warm. The tentaeula are very useful as tactile organs : while the 

 mane, forelock, and tail keep away insects, and the long hairs of the fetlock 

 and pastern protect these parts from the injurious effects of cold and wet, 

 and the action of foreign bodies.) 



HOBNT PEODTICTIONS. 



(Preparation. — The hoof and its contents may be examined by sections made in different 

 directions. The hoof can be removed by prolonged maceration, or by roasting on a fire, 

 when it may be cut and torn off by means of the farrier's knife and pincers.) 



The horny tissues form several groups the first comprises the horns of 

 Euminants ; the second, the so-called chesnuts of Solipeds ; the third, the 

 protective layer enveloping the digital extremities, and constituting the claws 

 of Carnivora, the Pig, Ox, Sheep, and Goat, and the hoofs of the Horse, Ass, 



