ECZEMATOUS DERMATITIS. 915 



with regular healing and leads to the formation of cracks, fissures, 

 and folds. Chronic proliferation then sets in around these, producing 

 in the hollow of the pastern ridge-like cicatrices, which can only 

 be removed by operation. 



During the acute stage the animals go very lame, especially for 

 the first few steps, but improve after a short time at exercise. 



Causes. Coarse-legged horses with long hair often surfer from this 

 form of dermatitis when working on wet ground. The epidermis is 

 continually moistened, becomes macerated, and inflammation is then 

 readily produced in presence of infective substances. The absence of 

 visible external cause, and the simultaneous appearance of disease in 

 several limbs, or in several animals in the same stable, gave rise to the 

 idea that mud-fever was a blood disorder, and should be regarded 

 as a metastasis or as erysipelas. Observations made on men, dogs, 

 and other animals, seem, however, to favour the belief that eczematous 

 disease may be associated with constitutional changes, which are at 

 present very imperfectly understood. Joly and Truche regard it 

 as contagious, although the specific organism is unknown. Truche 

 seems to rely on the fact that the disease attacked several horses 

 in a previously healthy stable after the introduction of some American 

 horses suffering from it. The fact that the same causes were acting 

 on a considerable number of animals at the same time was overlooked. 



Eczematous dermatitis is usually produced by external irritation 

 either of a mechanical, chemical, or specific character. The disease 

 often occurs soon after shoeing with high heels, because the changed 

 position of the foot favours the formation of folds in the skin just 

 above the heels, in which sand and dirt lodge and produce excoriation. 

 One of the commonest causes of mud-fever and of cracked heels in 

 town horses is to be found in the habit of washing horses' heels with 

 strong alkaline soaps (like soft soap) and hot water. The soap 

 irritates, and the hot water produces vascular relaxation and 

 congestion, which are liable to be followed by inflammation. Some- 

 what similar results are produced, in heavy horses, by washing the 

 legs with a cold-water hose after returning from the day's work. 

 Omnibus and cab horses, whose legs are only roughly rubbed dry 

 and are cleaned next morning with a brush, seldom suffer from any 

 of these forms of dermatitis. An excellent method of drying 

 and cleansing the legs simultaneously, is to rub them freely with 

 clean pine sawdust. Animals working on stubble or freshly-laid 

 roads or forest paths are apt to contract slight skin injuries, which 

 sometimes form the point of origin of disease ; the wound discharges, 

 macerate the epithelium, irritate the skin, and produce inflammation. 



