_Raising the toe_ by means of a tip, a full shoe with thinned branches or a toe-calk, _or paring away the quarters_ will tilt the os pedis backward, break the foot-axis backward in the pedal joint and to a less extent in the coronary joint, and increase the tension of the perforans tendon considerably and of the perforatus slightly. These tendons tightening behind the fetlock-joint force it forward, causing the long pastern to stand steeper, and taking some strain from the suspensory ligament. Hence, _the perforans tendon is under greatest tension, and the suspensory ligament under least tension, when the foot-axis is broken strongly backward_. _Shortening the toe, or raising the quarters_ by heel-calks or thickened branches, will tilt the os pedis forward, break the foot-axis forward in the pedal joint, and will _greatly lessen the tension of the perforans tendon_. The aggregate tension of perforans and perforatus tendons being diminished, the fetlock sinks downward and backward, the long pastern assumes a more nearly horizontal direction, and the tension of the suspensory ligament is increased. Thus, _the perforans tendon is under least tension, and the suspensory ligament under greatest strain, when the foot-axis is broken strongly forward_. D. The Elastic Parts of the Foot. [Illustration: FIG. 20. Os pedis and inner face of one lateral cartilage; _a_, toe of os pedis; _a′_, pyramidal eminence to which the extensor tendon attaches; _a″_, wing of pedal bone; _b_, lateral cartilage; _C_, points of attachment of suspensory ligament of lateral cartilage; _d_, point of insertion of ligament to the short pastern; _e_, point of insertion of ligaments from navicular bone.] All bodies which under pressure or traction change their form, but return again to their original shape as soon as the pressure or traction ceases, are called _elastic_ or _springy_. Nearly all parts of the horse’s foot, except the bones, possess more or less elasticity. The _lateral cartilages_ and the _plantar cushion_ are elastic to a high degree, but the _coronary band_, the _laminæ_, the _articular cartilage_, and the horny box or _hoof_ are less elastic. This property or characteristic is possessed by the respective parts of the foot in accordance with their function, location, and structure. [Illustration: FIG. 21. Plantar cushion seen from below: _a_, base or bulb of the plantar cushion; _b_, summit; _c_, median lacuna or cleft in which lies the “frog-stay” of the horny frog.] [Illustration: FIG. 22. Plantar cushion seen from above: _a_, base (bulbs) of same; _b_, summit; _c_, suspensory ligament of plantar cushion; _d_, place at which the elastic ligament connecting the os suffraginis and the lateral cartilage unites with the plantar cushion.]