914 DERMATITIS. 



X.- DERMATITIS IN THE FETLOCK REGION. MUD FEVER— 

 CRACKED HEELS— GREASE. 



The names " mud fever," " cracked heels," and " grease," have 

 been used since olden times to designate diseases of the skin about 

 the fetlock and particularly on its posterior surface. They vary 

 considerably in their nature and course, though certain characters 

 are common to all, viz., their point of origin in the heel, their 

 inflammatory nature, and spontaneous appearance. 



(a) Dermatitis erythematosa. This is the mildest form of dermatitis, 

 and is commonest in horses with thin fine skin; well-bred animals 

 suffer more frequently than heavy working-horses. In many 

 horses the skin of the pastern- joint seems exceedingly sensitive, 

 so that even the presence of sand in soft soils may cause irritation, 

 and give rise to this form of dermatitis. Similar results have been 

 noted after long-con tinued exposure to direct sunlight. The unpig- 

 mented skin appears red and rather painful, but after a few days 

 these symptoms disappear, and active desquamation sets in. The 

 disease consists of hyperemia of the papillary layer of the skin, 

 produces no permanent injury, and only occasionally requires special 

 treatment. When, however, the condition is neglected, and the 

 horse continues to work, this form of dermatitis may give rise to 

 the next in order. 



(b) Dermatitis eczematosa. Mud-fever, cracked heels. Eczema, 

 or inflammation of the skin, appears spontaneously, is ushered in 

 with swelling and redness, is usually soon followed by exudation 

 from the surface, and in general takes a typical course, which, 

 however, is less easily studied in this position than in others. The 

 swelling and redness are often scarcely visible, though there is 

 lameness, especially when the animals are first moved, whilst the 

 surface of the skin becomes covered with a yellowish-red fluid, 

 which soon dries to a brownish crust. The papular stage is 

 not well marked, though the vesicular stage, i.e., the formation of 

 small bladders, may sometimes be noted. The weeping stage 

 (stadium madidans) appears more distinctly, and is rapidly succeeded 

 by the formation of crusts (stadium crust osum). The crusts soon 

 loosen under proper treatment, and desquamation follows (squamous 

 stage), revealing normal epidermis. In characteristic cases the 

 process takes eight to fourteen days, and ends in complete recovery, 

 but not infrequently complications occur, especially if the animals 

 are worked during the disease. The movement of the inflamed skin 

 produced by walking, assisted by the presence of exudate, interferes 



