[Illustration:  Fig. 36.  I. LEFT FORE-FOOT SHOD AND MOUNTED TO RECOGNISE THE SINKING OF THE SOLE. a, Iron plate covering the inner half of the horny sole; b, openings in the same, with screw-holes for the reception of the contact-screw c (the part of the sole under the plate is covered with tinfoil, which at d passes out under the outer branch of the shoe, and becomes connected with the tinfoil of the wall; in order to give the freshly applied tinfoil a better hold, copying-tacks are at e passed through it into the horn, and one is similarly used to protect the tinfoil at the place where the contact-screw touches the latter); f, holes with screw thread for the fastening of the angle required to measure the movement of the wall, and also for the fastening of the conducting-wire, g; h, conducting-wire passing from the tinfoil; i, isolated nails.]

[Illustration:  Fig. 36.  II.  BAR-SHOE WITH OPENINGS. a, Near the inner margin and in the longitudinal bar; b, for the reception of the contact-screw c; d, openings for fastening the angle and the conducting-wires.]

After numerous experiments with the depicted contact-screws, moved to the various positions indicated in the drawings, the following conclusions were arrived at: 

1.  BEHAVIOUR OF THE CORONARY EDGE.—­During uniform weighting of all four hoofs the coronary edge shows a tendency to contraction in the anterior and lateral regions of the hoof, and a tendency to expansion posteriorly.  With heavy weighting of the hoof, which is shown by a backward inclination of the fetlock, contraction in the anterior and lateral regions is slight, but the expansion behind, in the region of the heels, is distinct, commencing gradually in front, becoming stronger, and diminishing again posteriorly.  The coronary edge of the heels becomes slightly bulged outwards.  The bulbs of the heels swell up and incline a little backwards and downwards.

When the fetlock is raised the expansion of the coronary edge of the heels disappears from behind forwards, passing forwards like a fluid wave.  In the lateral and anterior regions of the coronary edge the contraction disappears; and when the weight is thrown off the foot it passes into a gentle expansion of the coronary edge of the toe.  During the opposite movement of the fetlock, that of sinking backwards, this change of form is executed in the converse manner.

In short, the coronary edge resembles a closed elastic ring, which yields to pressure, even the most gentle, of the body-weight, in such a way that a bulging out of any one part is manifested by an inward movement of another part.

In Fig. 37, b, the dotted line represents the changes of form in comparatively well-formed and sound hoofs at the moment of strongest over-extension[A] of the fetlock-joint.

[Footnote A:  The term ‘over-extension,’ as employed by Lungwitz, is intended to indicate that position assumed by the fetlock-joint when the opposite foot is raised from the ground.]