KNlJE, FETLOCK, ANKI<E, AND FOOT. I93 



Canker. Canker of the foot is a disease due to the rapid reproduc- 

 tion of a vegetable parasite. It not only destroys the sole and frog, but 

 by setting up a chronic inflammation in the deeper tissues, prevents 

 the growth of a healthy horn by which the injury might be re- 

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

 other class. 



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

 course 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 prep- 

 aration 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 sufficient to induce the 

 disease. 



For some unknown reasons horses with lymphatic temperament, 

 thick skins, fiat 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 at- 

 tack 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 suc- 

 sessively affected. When the disease follows an injury which has ex- 

 posed 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 

 surrounding horn, until eventually a large part of the sole and frog is 

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

 certain points with particles of new, soft, yellowish, thready horn, 

 ■which are constantly undergoing maceration in the abundant liquid se- 

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



