68 ANATOMY OF VERTEBRATES. 



in the horizontal, plane. Moreover, in the rapid trot, each leg 

 rests a short time on the ground and swings a longer time. 



The gallop includes three combinations of movements of the 

 limbs. When the Horse begins the gallop on the right hind-leg, 

 the left one reaches the ground first ; the right hind and left fore- 

 legs next, simultaneously, and the right fore-leg last ; this is termed 

 the gallop of three beats. In the gallop where the four legs strike 

 the ground successively, the left hind-foot reaches the ground 

 first, the right hind-foot second, the left fore-foot third, and the 

 right fore-foot fourth ; this is the ' canter,' or gallop of four beats, 

 but it is not the kind of movement adapted for great speed. The 

 gallop wherein the legs follow the same order as in the trot — 

 that is, the left hind and right fore-feet reaching the ground simul- 

 taneously, then the right hind and left fore-feet — is the order in 

 which horses move their feet in racing, where the greatest speed 

 is required, and is called the gallop of two beats. In the ( amble,' the 

 two legs on one side rest on the ground and propel the centre of 

 gravity forward, whilst those on the opposite side are raised and 

 advanced, and, on taking a new position on the plane of motion, 

 the former pair are raised and advanced in a similar manner : 

 these successive actions are accompanied by considerable lateral 

 motion. This resembles the gallop of the Giraffe, and is a result of 

 special training in the Horse. In the ordinary gallop, the centre 

 of gravity moves in a vertical plane, and describes the path of a 

 projectile. The space passed over on the plane of motion is equal 

 to the horizontal velocity of the centre of gravity multiplied by the 

 time. According to Sainbell, the horse Eclipse, when galloping 

 at liberty and with its greatest speed, passed over the space of 

 twenty-five feet at each stride or leap, which he repeated 2^ times 

 in a second, being nearly four miles in six minutes and two seconds. 

 Flying Childers was computed to have passed over eighty-two feet 

 and a half in a second, or nearly a mile in a minute. In both 

 these famous racers the muscular system had been allowed to gain j 

 its full developement, as at four years, before being exercised for 

 the course : modern impatience strains and spoils the muscles by 

 the chief prizes being allotted to three-year-old horses. 



In many Marsupials and Rodents the hind-legs are shorter 

 than the fore-legs, the disproportion being greatest in the Kan- 

 garoos and Jerboas. In slow progression the Kangaroo supports 

 the body on the tail and fore-legs, while the hind-legs are simul- 

 taneously moved forward outside and in advance of the fore-legs ; 

 the base of support being here transferred from a triangle to 

 transverse line. In full speed the tail is rigidly outstretched 



