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CANKER. 



Canker of the foot is a disease due to the rapid reproduction of a 

 vegetable parasite. It not only destroys the sole and frog, but by set- 

 ting up a chronic inflammation in the deeper tissues, prevents the 

 growth of a healthy horn by which the injury might be repaired. 

 Heavy cart horses are more often affected than those of any other class. 



Causes.— The essential element in the production of cankers is of 

 coarse the presence of the parasite; consequently the disease may be 

 called contagious. But, as in all other diseases due to specific causes, 

 the seeds of the disorder must find a suitable soil in which to grow be- 

 fore they are reproduced. It may be said, then, that the conditions 

 which favor the preparation of the tissues for a reception of the seeds 

 of this disease are simply predisposing causes. 



The condition most favorable to the development of cankers is damp- 

 ness—in fact, dampness seems indispensable to the existence and growth 

 of the parasite; for the disease is rarely, if ever, seen in high, dry dis- 

 tricts, and is much more common in rainy than in dry seasons. Filthy 

 stables and muddy roads have been classed among the causes of canker ; 

 but it is very doubtful if these conditions can do more than favor a 

 preparation of the foot for the reception of the disease germ. 



All injuries to the feet may, by exposing the soft tissues, render the 

 animal susceptible to infection ; but neither the injury nor the irritation 

 and inflammation of the tissues which follow, are suflicient to induce the 

 disease. 



For some unknown reason horses with lymphatic temperaments, 

 thick skins, flat feet, fleshy frogs, heavy hair, and particularly with 

 white feet and legs, are especially liable to canker. 



Symptoms. — Usually, canker is confined to one foot ; but it may attack 

 two, three, or all of the feet at once; or, as is more commonly seen, the 

 disease attacks first one then another, until all may have been succes- 

 sively affected. When the disease follows an injury which has exposed 

 the soft tissues of the foot the wound shows no tendency to heal, but, 

 instead, there is secreted from the inflamed parts a profuse, thin, fetid, 

 watery discharge, which gradually undermines and destroys the sur- 

 rounding horn, until eventually a large part of the sole and frog is dis- 

 eased. The living tissues are swollen, dark-colored, and covered at cer- 

 tain points with particles of new, soft, yellowish, thready horn, which 

 are constantly undergoing maceration in the abundant liquid secretion 

 by which they are immersed. As this secretion escapes to the sur- 

 rounding parts it dries and forms small cheesy masses composed of the 

 partly dried horny matter, exceedingly offensive to the sense of smell. 

 When the disease originates independently of an injury, the first evi- 

 dences of the trouble are the offensive odor of the foot, the liquid secre- 

 tion from the cleft and sides of the frog, and the rotting away of the 

 horn of the frog and sole. 



