DISEASES OF THE SKIN 137 



Papules, lueaiiiiig pimples, are of various kinds, ranging from minute 

 specks due to excess of blood in the papillae of the skin, to the larger 

 elevations caused by distension of the follicles, or by the deposition of 

 lymph around them, or by solid deposits in the true skin. There are 

 also papules or pimples formed by the collection of sebaceous secretion 

 within the follicles, and others resulting from hypertrophy or overgrowth 

 of normal structures, forming minute fibrous excrescences or small warts. 



Vesicles are really small bladders or blisters containing a watery 

 Huid; they naturally vary in size according to the amount of fluid which 

 they contain. When the bladders are sufficiently extensive to be de- 

 scribed as large bladders they are termed hullce; thus, as the result of an 

 ordinary blister, large and small water bladders, otherwise vesicles and 

 bullee, will easily be distinguished. 



Pustules. — These elevations are distinguished from vesicles by their 

 contents. While the vesicle contains clear watery fluid, the pustules 

 always contain pus, and are the result of more active inflammation than 

 occurs in simple vesicular eruption. Vesicles in some diseases become 

 converted into pustules as a consequence of a more intense inflammation 

 arising in the course of the ailment. 



Squamae. — The word is used to indicate scales, which are obvious 

 enough on a mere cursory examination. A scaly condition of the skin 

 may be an accidental condition, and simply denote want of cleanliness, 

 or it may be an indication of irritation of the surface, or the outcome of 

 some specific disorder. 



Pityriasis, or bran disease, is not uncommon in the horse, and is a 

 good illustration of the condition of skin which is described as squamous. 



Tubercula are small lumps or large pimples, which are hard and 

 circumscribed, and are commonly permanent. Occasionally they undergo 

 slow suppuration, but ordinarily remain as small fibrous tumours, which 

 are of no special significance unless they occur on parts of the body with 

 which the harness is brought into contact, as on the shoulders and back. 



Besides these changes in the skin which have been described, there are 

 to be found crusts or scabs which consist of the dried exudation matter dis- 

 charged from a broken surface. They vary in their appearance according 

 to the character of the discharge, to the drying of which they owe their 

 origin. 



Ulcers are well known as complications m certain forms of skin disease. 

 They consist really in destruction of the tissues of the true skin^ arising 

 either from simple inflammation, or from a specific disease, as in glanders. 



Excoriations are those superficial injuries due to the removal of the 

 cuticle by friction between two surfaces of the skin, or by the act of 



