The Polo Pony.—Handiness and speed, with sufficient staying and weight-carrying power, are the two chief requirements of the polo pony. Consequently, he should be light in front, should carry his head and neck well, have sloping shoulders, strong hocks, and his hind legs well under him. The fact of his being rather " goose-rumped " will be no detriment. These views are strengthened by the remarks made on pages 310 and 311 about the conformation of the zebra; for the polo pony, like his striped relative, requires great ability of suddenly stopping, turning round, and galloping off in the opposite direction. This turn has to be done chiefly on the hind legs, which in this case will be more or less bent, and will then have full power to project the pony in the new direction. The best English polo ponies, such as the once matchless Dynamite, are animals which, but for an accident of breeding, would have been high-class hunters or brilliant chasers.
Points of Horse pp392-95
another horse so called Hack pp389
The Hack.—The chief points about the hack are that he should be " light in front," have sloping shoulders, and sound legs and feet, so that he may be sure-footed and able to stand work ; and he should be rather high in front (pp. 177 and 178). The conformation of his head and neck should be such as to allow him to bend readily to the rein. The action of the hack should be somewhat " high" and should be " true," so that, when viewed from behind, the near pair of limbs, in the walk, trot and canter, should move in a line parallel to that of the off pair. Action, good looks, and a showy carriage of the head and tail are essentials in the high-priced hack.
According to hipologist Juan Carlos Altamirano, great historian and specialist on the Pura Rasa Espanola or Spanish Horse, the XVI century nondescript hacks or 'haquas' imported from England, Northern Europe and Poland were foundation horses along with particular Barb, Neapolitan and Andalusian stallions and Marismenas mares when king Felipe II (Philip II) ordered creation of the breeding program at the Yeguada Real in Cordoba, Spain in 1567 AD.
H. Hayes' entire book can be read here, but my text belongs to 1904 edition and the photos of the horses given in the text as well http://books.google.com/books?id=P1sCAAAAYAAJ&printsec=frontcover&source=gbs_atb#v=onepage&q&f=false
at the top some old sketch of mine