144 NAVICULARTHRITIS. 



under ordinary but under extraordinary circumstances. A foot 

 with a sound and prominent frog is in a condition to receive the 

 disease; while one with a shrunk, shrivelled, and especially a dis- 

 eased frog, enjoys a sort of immunity from taking it — is, in fact, 

 as I shall shew, protected from an attack of navicularthritis. 



Predisposition. — The notorious fact of the foot in a condition 

 to receive navicularthritis, or actually attacked by the disease, 

 presenting a hoof which for normal aspect might be selected as a 

 specimen of health, with a frog such as Coleman would have pro- 

 nounced to be perfection, while it puzzles the non-professional 

 man, is at once seized upon by the veterinary surgeon, supposing 

 the horse to be lame of the foot, as pathognomonic of the nature 

 of the case. Beholding so good-a-looking foot, and yet a lame 

 foot, his suspicions become at once aroused, and the probability 

 is, that, investigation into the cause of the lameness confirms them. 

 Contraction has certainly nothing to do with the case; on the con- 

 trary, the foot is open at the heels, and presents a bold prominent 

 frog, a frog that has evidently been all along receiving a full 

 amount of pressure from the ground, and been in full play in con- 

 sequence, and so has warded off contraction. Whenever con- 

 traction proves to be an accompaniment of navicularthritis, one 

 disease will be found to be the sequel of the other : contraction 

 of the hoof being almost certain to supervene upon such constant 

 favouring of the foot as the pain and lameness of navicularthritis 

 necessarily entails. 



The contracted foot, I repeat, with its high heels, and its raised and 

 shrunken, and perhaps diseased frog, may be regarded as possessing 

 a kind of protection from navicularthritis ; and, presently, we shall 

 perceive the reason of this. The curious correlative fact, however, 

 is, that neither is the broad or flat foot, no more than the narrow 

 one, the subject of disease in the navicular joint. If violent pressure 

 to the frog be — as I think I shall be able to demonstrate that it is — 

 fruitfully productive of navicularthritis, how comes it that flat feet, 

 in which frog pressure is remarkable, should be exempt from or in- 

 susceptible of it 1 The answer to this question is, that such is the 

 normal thinness or weakness of the horn of such feet, and such 

 their consequent properties of elasticity and yielding, that pressure 



