We may now direct our attention to the horse's action, for which purpose he should first be made to walk about 50 yards backwards and forwards, with his head as free and unrestrained as it can possibly be allowed. The common practice of taking hold of the bridle close to the bit, and forcing up the head, as usually adopted by the expert nagsman, adds very considerably to the difficulty of forming a diagnosis in the slighter forms of lameness, and may be the means of causing them to be altogether overlooked. The animal may now be turned short round from right to left, and from left to right, and then caused to move in a backward direction. During this test it will be noticed whether the action is close, and such as to cause brushing, or interfering, and whether there are any indications of stringhalt or shivering. The former will be indicated by a spasmodic upward jerk in one or both hind limbs - rarely it may occur in the fore ones - while the latter is recognized by a difficulty in backing, during which the muscles of the quarter and the tail are thrown into a tremulous condition (fig. 533). Although both these affections constitute unsoundness, it must be borne in mind that animals that suffer from them are generally capable of performing a considerable amount of useful work; and further, that either of them may exist in such an incipient condition as only to be perceived on rare occasions. It cannot therefore be said that because a horse does not exhibit signs of their presence at the time of the examination he is necessarily free from them.
Lameness when present is not always developed by walking, but may only appear in the faster paces, and even then it may not be displayed until weight is placed on the back. It is therefore necessary to a thorough examination that the horse be trotted for 50 yards in hand backwards and forwards on a loose rein, at au easy pace, and then again under saddle, first on soft ground and then on hard. While this is going: on, his movements should be carefully criticized, both as to the natural action, which may be close and "brushing", as well as to the presence of actual lameness.
There is an idea in the minds of some that where lameness exists the affected animal " drops" on the lame limb, but, as matter of fact, the reverse is the case. When the unsound leg is on the ground the head is elevated, in order that the muscles may relieve it of a certain amount of weight, and when the sound limb meets the ground the head " drops" with it. The same kind of movement is observed where lameness occurs behind. It is well known that lameness is aggravated when passing from soft to hard ground, and some veterinarians have regarded this phenomenon as indicating the foot as the seat of trouble. Our experience is, that when the cause of lameness is in the foot the difference in the intensity of lameness in passing from the softer to the harder surface is greater than when the cause is elsewhere, but we do not consider that the test is of any diagnostic value.