ECZEMA. 



509 



hair constitutes a preferred location for numerous parasites (lice, 

 trichodectes, etc.). This disease is, therefore, most commonly found 

 on badly kept farms and in countries where, on account of certain 

 prejudices or superstitious belief, the grooming of the horse is 

 neglected (Tartary, Russia, Poland, etc.). A cause which is en- 

 tirely the opposite of the precediug, is the abuse of soap on the 

 mane ; if the soap is not removed with a free use of water, it becomes 

 the agent of a repeated or permanent irritation of the skin of the 

 neck, and may produce eczema. 



Prolonged dampness of the mane (through rain water, repeated 

 washings), leads to maceration of the epidermis and decomposition 

 of the normal secretions of the skin (sebaceous matter, perspiration), 

 like rain rot of the sheep; it thus becomes a direct cause of eczema, 

 which is produced so much easier on accouut of the fine and tender 

 condition of the skin of the regions protected by the mane, which are 

 thus specially predisposed to this disease. Anterior inflammatory 

 processes which have more or less modified the condition of the 

 skin favor a recurrence of the trouble (squamous eczema). 



Symptoms. The first manifestations of eczema on regions cov- 

 ered with horse-hair (the mane) often pass uuobserved, either on 

 account of neglect in the care of the skin, or because the dermal 

 lesions are masked by the cutaneous exfoliation. It is only when 

 the decomposed inflammatory products have aggravated the disease 

 that the owner observes the alterations of the hair and symptoms 

 of pruritus. The animals scratch and rub themselves, they bite 

 the diseased parts. The lesions are then generally the following : 

 the skin is covered with a serous, purulent, bloody, or scabby 

 exudate ; vesicles and pustules are often observed in it ; the hairs 

 of the mane and tail are agglutinated by perspiration and by a 

 fatty, sticky, dirty, fetid matter ; they become firmly packed in a 

 more or less thick layer (Polish plica). Later, when the inflamma- 

 tory process is extended to the hair follicles, the character of the 

 horse-hair is modified ; the hairs become fragile, curl, and through 

 the irregularity of direction the felting which characterizes plica is 

 favored. Upon other regions where the animals rub or bite them- 

 selves easily (at the tail, for instance), the hairs become atrophied 

 and fall. The skin of the caudal appendage becomes gradually 

 sclerosed, thickened, and indurated, the cutaneous papillse become 

 depressed, the horse-hairs do not grow again (rat tail). This is the 

 chronic state of squamous eczema. 



