634 A MANUAL OF VETERINARY PHYSIOLOGY 



air with the fore and hind legs crossed like a pair of scissors ; next a 

 thrust with a diagonal hind-leg, which shoots it once more into the 

 air, alighting on a lateral fore-leg. Consequently, in a single stride 

 of the greyhound there are two springs, once from a fore-leg and 

 once from a diagonal hind-leg. 



The Footprints occurring during the various paces of the horse 

 have been previously referred to ; they are illustrated in Fig. 212. 

 Before the days of instantaneous photography a great deal of atten- 

 tion was paid to them as a graphic record of locomotion, and nothing, 

 perhaps, better illustrates how differently horses move while per- 

 forming the same pace, or even the same horse at different times. 

 The differences do not, of course, lie in the modes by which the 

 limbs are moved, but the length of the steps taken and the position 

 of the feet relative to the central line of the body. In the walk, for 

 example, the hind-feet may be placed down immediately on top 

 of the impressions of the fore, or they may be placed in front of or 

 half covering the fore-prints. The only real interest now attached 

 to a study of footprints lies in the information they furnish of the 

 extent to which the feet are brought under the middle line of the body 

 as a means of support. This is ascertained by the use of a line so 

 adjusted as to lie midway between the tracks made by the near and 

 off feet. Such a line represents the middle line of the body. It 

 might at first sight be reasonable to suppose that the off feet would 

 fall to the right and the near feet to the left of such a line, and that 

 the distance the impressions were made from the central line, would 

 be represented by a line passing midway between the feet during 

 repose. But this is not so ; a pair of fore-feet 5 inches apart during 

 repose, may be shown during locomotion to be brought completely 

 under the middle line of the body, or even to cross it. During the 

 slowest paces the feet are planted very nearly or quite in a line with 

 the centre of the body ; during the faster paces they may be brought 

 so far under from each side as to cross the central line. In the 

 gallop the feet are brought well under the central line of the body, 

 forming a very straight track, occasionally broken by being planted 

 away from the centre, or sometimes completely crossing the centre 

 to the opposite side of the body. All the features discussed 

 may be seen on inspection of the various foot-tracks shown in 

 Fig. 212. The dotted line represents the middle line of the body. 



Summarising these results, we see that, though in repose the 

 feet may be 4 or 5 inches apart measured from their inside edge, 

 the tracks these feet leave on the ground do not show this interval ; 

 on the other hand, they are brought well under the centre of the 

 body, sometimes even crossing it, and the faster the pace, the nearer 

 the footprints approach a straight line. It is obvious that the more 

 the feet are brought under the middle line of the body, the more 

 stable the support afforded, but it is not clear how they are able to 

 avoid striking their fellows. 



The Jump. — It is said that no two horses jump alike, and 

 even that the same horse under identical conditions will jump 

 differently. The differences alluded to originate in the manner 

 in which the hind-legs are handled preparatory to collecting 

 the body for the spring upwards. Under ordinary circumstances, 

 as the jump is approached, the animal is steadied in his stride, 

 in order to afford him the needful opportunity of ' collecting ' 



