NAVICULARTHRITIS. 147 



ment, than from hard or continued work ; and we shall universally 

 find that those of the fore or hind extremity suffer most, in parti- 

 cular the navicular or hock joints, according as they have respect- 

 ively been the most called into action. We see this exemplified 

 in hunters, racers, chargers, hackneys, carriage or coach horses, &c. 

 It is an axiom in practice with every veterinarian of experience, 

 that lameness in the fore limb has for its ordinary seat the foot, 

 in the hind limb, the Kock ; and, as we have seen, when we 

 come to reason physiologically on the subject, science completely 

 bears us out in accounting for these apparently paradoxical local- 

 ities of lameness. 



But why should not the coffin suffer as well as the navicular 

 joint, that entering equally into the construction of the pedestal of 

 the column of the fore limb ? This shews there must be something 

 more, besides the circumstance of its nethermost situation in the 

 column of support, to account for the navicular joint being so fre- 

 quent a seat of injury, while the coffin is, in fact, a part rarely dis- 

 eased. And I cannot, myself, satisfactorily account for this but on 

 the principle of frog-pressure, or, rather, frog-contraction. The 

 facts already stated, of navicularthritis having become so frequent 

 a disease since frog-pressure became so fashionable in the practice 

 of shoeing, compared to what we have reason to believe it was be- 

 fore, and of its invariably happening in feet presenting sound pro- 

 minent frogs, militate most strongly in favour of this opinion : at 

 the same time, there may be something in causation ascribable to 

 the circumstance of the navicular jbrn^, as we denominate it, being 

 one which owes its formation to the main tendon of the fore leg in 

 connection with bone. We know that one of the uses of the frog 

 is to serve as a stop or stay to the foot; and where horses in action 

 are suddenly pulled up, or in their descent from leaps have to sus- 

 tain themselves by firm footing upon the ground, they throw them- 

 selves at once upon their heels and frogs, and in such efforts and 

 shocks, no doubt, frequently do mischief to the navicular joints, 

 and particularly when their hoofs, from standing in the stable or 

 lack of moisture, have become hard and dry and inelastic. In the 

 act of standing for any length of time, and in any efforts that may 

 be required to sustain that posture, it would be the coffin-joints, 



