[Illustration: FIG. 9.—Drawing (of the actual size of the original) of a flat carving in shoulder-bone, of a horse’s head, showing twisted rope-bridle and trappings. _a_ appears to represent a flat ornamented band of wood or skin connecting the muzzling rope _b_ with other pieces _c_ and _d_. This specimen is from the cave of St. Michel d’Arudy, and is of the reindeer period. This, and others like it, are in the museum of St. Germain.] Some of the engravings of horses’ heads seem to indicate the existence of a horse alongside the commoner form with a narrower, more tapering face, and may possibly be due to the introduction, even at that remote period, of another race distinct from the Northern or Mongolian wild horse. That this admixture of a distinct and more slender horse with the Northern horse has taken place over and over again in historical times is a matter of knowledge. The question is, when did it first take place, and where did the more slender horse come from? In later days we know this more shapely breed as the Arab and the Barb, and the introduction of its blood at various times into the more Northern stock is well ascertained. The latest great historical case of such admixture is the production of the English thoroughbred in the eighteenth century by such sires as the Darley Arabian, the Godolphin Barb, and the Brierley Turk, whose blood is transmitted to modern racehorses through the great historic sires, Herod, Matchem, and Eclipse, the ancestors of practically all modern racehorses.