ANATOMY AND PHYSIOLOGY. 



TEGUMENTARY SYSTEM. 



ON THE HAIR OF HORSES. 



Hair is a peculiar tegumentary appendage, 

 characteristic of the horse and other rtiam- 

 mals. It is developed on the interior of 

 ollicles which are formed by a depression of 

 the true skin. These follicles are lined by a 

 continuation of the epidermis, the cells of 

 which are developed in peculiar abundance 

 from a spot at its deepest portion ; the dense 

 exterior of the cluster thus formed being 

 known as the bulb of the hair, while the 

 softer interior is termed its pulp. The 

 elementary parts of hair are: a cortical or 

 investing substance of a dense horny tex- 

 ture; and a medullary or pith-like sub- 

 stance, of a much softer character, occupy- 

 ing the interior. The cortical envelope of 

 hairs is a continuation of the outer scaly 

 layers of the epidermis that lines the follicle ; 



whilst the medullary is derived from the 

 deeper stratum whose cells are produced in 

 unusual abundance at the coecal extremity ; 

 and it is by the constant development of 

 new cells at this point, that the continual 

 growth of the hair is kept up. 



An excoriation or moulting of the hair, 

 which falls off, is replaced by a new growth, 

 which as it comes to maturity assumes the 



original color. 



This change in the covering 



with which nature has so wisely clothed 

 the horse, usually takes place either in spring 

 or autumn, or at both periods. The hair 

 of the mane and tail, however, is not sub- 

 jected to these periodical changes; hence, 

 it acqukes considerable calibre and length. 



By analysis, the hair yields carbon, hy- 

 drogen, nitrogen, oxygen, and sulphur, and 

 its variation in color is due to the presence 

 of different shades of matter which infil- 

 trates the cortical substance. 



EXAMINATIONS ON THE CO]\IMON INTEGUMENTS. 



Q. Of how many parts do the common integuments 

 consist ? — A. Three : cuticle, cutis, and rete mucosum. 



Q. Describe the cuticle or epidermis ? — A. It is a 

 thin, transparent, tough, and elastic jjorous membrane, 

 ser\ing as an envelope to the cutis, or true sldn. It is 

 composed of flexible lamellae, so arranged as to bear 

 some analogy to the scales of lish ; it pervades the 

 whole body, and insinuates itself into jiorous struc- 

 tures and follicular passages, inlets, and outlets of the 

 system ; it is supposed to be continous from the mouth 

 to the anus. 



Q. Describe the pores or perforations. — A. There 

 are three. First, those surrounding the hair. Sec- 

 ondly, exhalcnt pores. Tliii'dly, absorbent pores. 



Q. How is the cutis designated? — A. As the cutis 

 vera, or true skin. 



Q. "VYhat is the structure of the cutis ? — A. It is of 

 a fibrous texture, tough, elastic, vascular, and highly 

 eensitive, and is what we commonly denominate leather. 



Q. What are the attachments of the cutis? — A. 

 The cutis is attached to the subjacent parts by cellu- 

 lar membrane, in some places so tensely that httle or 

 no motion is admitted of; in others so loosely that it 

 admits of being tlu'o\ATi into folds. About the forehead, 

 ujDon the back, around the tail, and upon the pasterns, 

 it can scarcely be pinched up ; but upon the sides of the 

 face and neck, upon the ribs, along the flanks, and upon 

 the anus and thighs, it will easily admit of duplication. 



Q. What varieties are there in the density of the 

 cutis ? — A. It varies in density, not only where it covers 

 different parts in the same animal ; but in horses of 

 different breeds and temperaments, it varies very essen- 

 tially. 



Q. AVhat is the organization of the rete mucosimi ? 

 A. It is composed of a fine, delicate, laminated tissue, 

 interposed between the cuticle and cutis, and serves as 

 their connecting medium, and is supposed to secrete 

 the coloring matter of the external surface and hair. 



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