Extreme and forcible flexion of the corono-pedal articulation also sometimes gives evidence of tenderness.  In this case the foot is held up, the animal’s metacarpus resting on the operator’s knee, and the toe of the hoof pushed downwards with some degree of force.

The same movement of the joint is given by causing the animal to put full weight upon the diseased limb, a small wedge of wood being first placed under the toe.  In this manner the pressure of the perforans tendon upon the bursa is greatly increased, and the animal is caused to show symptoms of distress.

The lameness may also be increased, and diagnosis helped, by paring the heels, so as to leave the frog prominent and take the whole of the body-weight.  The same end is also obtained by applying a bar shoe.  This was originally pointed out by Brauell, and is quoted by Zundel and by Moeller.

The changes in the form of the hoof may now be noticed.  These are largely dependent on the fact that more or less constantly the patient saves the heel.  The horn of the walls in this region, and the horn of the frog, is thereby put out of action and induced to atrophy.  The hoof gradually assumes a more upright shape, and the heels contract.  We thus get a hoof which is visibly narrowed from side to side, with a frog that is atrophied and often thrushy, and with a sole that is abnormally concave, hard, and affected with corns.

When occurring in the hind-feet—­a condition that is rare, but which has been noticed by Loiset, and quoted by Zundel—­the animal is stiff behind, walks on his toes, and gives one the impression that he is suffering from some affection in the region of the loins.

One such case is reported by an English veterinary surgeon, and we quote it here: 

’A gray gelding, and a capital hunter, the property of a gentleman in this neighbourhood, became lame in the near fore-foot after the hunting season of 1859.  The lameness was believed to be due to navicular disease.  The operation of neurectomy was ultimately had recourse to.  The horse subsequently did his work as well as ever, and was ridden to hounds regularly till the end of the year 1861, when he went lame of the off fore-foot.  From this date he also showed very peculiar action behind, and was at times lame of both hind-limbs without any apparent cause.

’In the year 1862, from the groom’s indiscreet use of physic, superpurgation was brought on which caused the animal’s death.  On a post-mortem examination being made, the horse was found to have navicular disease of all four feet.  It is worthy of note that this horse had always “extravagant” action behind, but was a remarkably quick and good jumper.’[A]

[Footnote A:  F. Blakeway, M.R.C.V.S., Veterinarian, vol. ii., p. 21.]