308 DISEASES OF THE HORSE'S FOOT 



sensitive frog and sole, and destroys their connections with 

 the horny covering. 



The use of the word ' fungoid/ and particularly that of 

 ' inoculate,' is suggestive enough, and is evidence sufficient 

 that either Blaine or his editor recognised, simply through 

 clinical observation, the working of a special cause. 



Four years later, Bouley is found holding the opinion that 

 canker was closely allied to tetter, thus recognising for it 

 a local specific cause. The same observer also pointed out 

 that the secretion of the keratogenous membrane instead 

 of being suspended was greatly increased, taking care to 

 explain, as did Dupuy, that the products of the secretion 

 were perverted and had lost their normal ability to become 

 transformed into compact horn. 



In 1864 this slowly growing recognition of a specific 

 cause received further impetus from the statements of 

 Megnier. This observer claimed to have discovered in the 

 cankerous secretions the existence of a vegetable parasite 

 (namely, a cryptogam, as in favus), which he termed the 

 keraphyton, or parasitic plant of the horn. 



Modern research, though failing to substitute anything 

 more definite, has not confirmed this. The exact and ex- 

 citing cause of canker is therefore still an open question, 

 and a matter for research. We may, however, sum the 

 matter up by briefly discussing the causes, so far as clinical 

 observation teaches us. This we shall do under two head- 

 ings — namely, Predisposing and Exciting. 



Predisposing Causes. — Starting with the assumption that 

 the disease is due to local infection, we may relate as pre- 

 disposing causes anything having a prejudicial effect upon 

 the horn, disintegrating it, and so laying the tissues beneath 

 open to attack. The most prominent in this connection is 

 certainly a continued dampness of the material on which 

 the animal has to stand. Particularly is this the case 

 when the material is also excessively foul and dirty, con- 

 taminated with the animal discharges, and presumably 

 swarming with the lower forms of animal and plant life. 

 We shall therefore find bad cases of canker in stables 



