File:The Horse - its treatment in health and disease, with a complete guide to breeding, training and management (1905) (14591802180).jpg

Identifier: horseitstreatmen09axej (find matches)
Title: The Horse : its treatment in health and disease, with a complete guide to breeding, training and management
Year: 1905 (1900s)
Authors: Axe, J. Wortley
Subjects: Horses
Publisher: London : Gresham
Contributing Library: Webster Family Library of Veterinary Medicine
Digitizing Sponsor: Tufts University

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6, Horse. being reduced to a very .slender rudiment. In this animal the ulna(fig. 669) is well developed, but the fibula has become quite rudimentary;the forms of the molar teeth have not undergone very considerablechano-e. In the Miohijjpus, the contemporary of the Anchitherium of Europe,the extremities remain nearly as in the Mesohippus. The ulna has thelower part greatly reduced; the other limb-bones remain nearly thesame. To the Miocene period also belongs the Merychippus, found throughouta large portion of North America, which is remarkable in that in the youngcondition it has the short-crowned, uncemented teeth of its ancestors,while the adult animal has the long-crowned and cemented teeth of itssuccessors. Proceeding upwards to the Protohippus and its near relative theEuropean Hipparion from the Lower Pliocene, it appears that the changescliiefiy relate to the ulna, which in these animals has decreased consider-ably in length, only reaching to the middle of the radius. The two
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COMPARISON OF THE FORE AND HIND FEET OF THE HORSEWITH THOSE OF SOME OF ITS ANCESTORS I. Phenaccdus. 2. Protorol.ippus. 3. Mcsohippiis. 4. Mioliijipus and Anchitheiiun,. 5 Protohippus. 6. Hipparion.7. Horse. (All these figures are drawn to one scale.) FOSSIL ANCESTOKS OF THE HORSE 513 extra toes in the fore- aiul hind-feet still remain, but they are evidentlyshrinking in size. The changes in the molar teeth are also very con-siderable. As will be seen on reference to fig. 668, the teeth are passingfrom the brachydont or short-crowned to the hypsodont or high-crownedvariety, a change which goes on progressively in correspondence with thevanishing of the extra digits. In the upper molars of the Hi23parionthere is a distinctive feature which is at once recognized by the anatomist,in the presence of an interior column of dentine completely isolated fromthe rest of the mass, as shown in the section of the upper molar(e, fig. 667) close to the bottom, in the form of a white oval spotsurround

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