DISEASES. 601 



As with other parasitic diseases, canker is communicable by- 

 contagion ; although the examples are quite rare they cannot be 

 doubted. Hutrel, d'Arboval, Plass, Blind and Megnin have ob- 

 served them, and in all the cases dampness has contributed to 

 the propogation of the cryptogam. 



The lymphatic constitution in. an animal is eminently propi- 

 tious to the development of canker, as it is observed to be, in fact, 

 for all parasitic diseases. 



It is known by daily observation of facts that horses whose 

 skin is thick, with the hairy system well developed, the feet flat, 

 with thick frogs, are more often affected with canker than animals 

 of a nervous constitution. It is more particularly observed in 

 horses with much white at then- extremities, with stockings and 

 white feet, and in those where there is a tendency to albinism. 



An, unknown diathesis has also been considered as causing a 

 predisposing constitutional organic condition, but this has not 

 been justified by observation. It may happen that canker cured 

 or dried on one foot, may attack another foot, perhaps a third, 

 and then a fourth, to re-appear in the first ; this character of the 

 disease has often been mentioned as proof of this diathesio condi- 

 tion ; but it may also be explained by its contagious character. 

 The disease remains too much localized to be constitutional, as 

 generally in diathesio diseases we have critical eruptions upon 

 different organs or different tissues. 



Treatment. — From the preceding remarks, it is evident that 

 in feet affected with canker, the keratogenous apparatus of the 

 foot has undergone no essential alteration in its structure, that its 

 thickness and density have only increased by consequence of the 

 infiltration and organization in its net-work of the plastic products 

 of inflammation. And, again, the secreting function of this appa- 

 ratus, far from being arrested, is on the contrary, more active ; but 

 the products it gives instead of being conerescible, remain difflu- 

 ent ; hence the impossibihty for the hoof to be restored in the 

 regions where this alteration of secretion exists and remains. 

 These important facts, says M. Bouley, must take the lead in the 

 chapter of the therapeutics of canker, because they .teach the 

 practitioner that the object to effect, in the treatment of this dis- 

 ease, is not to radically destroy the diseased tissues, as has been 

 too often done and recommended, but to return to them their 

 physical and physiological properties by the appHcation on their 



