342 THE SKLV AND ITS DISEASES. 



CHAPTER XV. 



THE SKIN AND ITS DISEASES. 



The skin of tlie horse resembles in construction tliat of other animals. 

 It consists of two chief parts, viz., the cuticle and cutis, materially 

 differing in their structure and oflBce. The outer one is the cuticle — - 

 the epidermis or scarf-skin, extending over the whole external part of the 

 animal. It is composed of two parts, the extenial or scaly, and the internal 

 or cellular. If the epidermis is examined by means of a microscope, the 

 existence of the scales somewhat like those of a fish Avill be readily detected 

 on its surface. There is always a singular change taking place in this 

 outward covering of the animal, a constant alteration and renewal of every 

 part of it, and the scales which fall off in the shape of dandriff are the cells 

 of which the internal portion of the epidermis is made up, having under- 

 gone compression, on their being forced upward to the surface of the skin. 

 Tn the action of a blister they are raised from the skin beneath, in the 

 form of pellucid bladders, and in some diseases are thrown up in hard, dry, 

 white scales, numerous layers of which are placed one above another. The 

 cellular portion of the epidermis is in contact with the papillated surface 

 of the cutis or true skin, from which it is secreted. The name of rete mu- 

 cosum has been given to this part of the epidermis from its web-like 

 structure and soft mucous consistence. In the cells of which it is made up, 

 the material which gives colour to the animal is secreted. In horses with 

 white hair the rete mucosum is white ; it is brown in those of a brown 

 colovu' ; black in the black, and in patches of different colours with those, 

 the hue of whose integument varies. The cuticle does not possess either 

 nerves or blood-vessels ; it is therefore devoid of sensibility, but it fulfils a 

 most important function in furnishing a protection to the parts beneath, 

 which are so often exposed to a morbid sensibiHty. In every part of the 

 body the cuticle is perforated by innumerable pores, some of which permit 

 the passage of the hair ; through others the perspii-able matter finds a pas- 

 sage ; while from others various unctuous secretions make their escape. The 

 cutis or true skin lies beneath the rete mucosum. Like the cuticle, it 

 consists of two principal parts, the upper or papillated, and the coi'ium or 

 deeper layer. The papillated layer lies beneath and in contact with the 

 rete mucosum or cellular portion of the epidermis, and is so named from 

 numerous conical prominences or papdlas on its surface. It is exceedingl;y * 

 vascular, highly sensitive, and differently arranged in vaiious parts of the 

 body. The sensitive lamina of the foot is the papillated sui-face of the 

 dermis, arranged in a different manner. Beneath tliis we have the corium, 

 made up principally of areola mixed mth white and yellow fibrous tissue. 

 The corium makes up the chief thickness of the skin, and constitutes the 

 phant and yielding part of it. It varies in its structure in different animals ; 

 in the better bred one we have a larger development of the yellow elastic 

 tissue, and in the coarser breed a large amount of white fibrous tissue. 

 It is the substance which is converted into leather when removed 

 from the body, and binds together the different parts of the frame. In 

 some places it does this literally, and chngs so closely to the substance 

 beneath that it scarcely admits of any motion : this is the case about the 

 forehead and the back, while upon the face, the sides and flanks, it hangs 

 in loosened folds. In the parts connected Avith progression it is folded 

 into various duplicaturcs, that the action of the animal may admit of the 



