Identifier: horseitsrelative00lydeuoft (find matches)
Title: The horse and its relatives
Year: 1912 (1910s)
Authors: Lydekker, Richard, 1849-1915
Subjects: Donkeys Equidae Horses Zebras
Publisher: New York : MacMillan
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
ome of the extinct ancestors of the horse, and areof importance as showing that the three largefunctional premolars of the latter correspond to thethree last of the typical mammalian series of four.Hence it is frequently found convenient to speakof these teeth as the second, third, and fourth pre-molars, instead of calling them the first, second, andthird. On the other hand the three pairs of molarsare respectively denominated the first, second, andthird. In a young colt, if the wolf-teeth be not de-veloped, there are three pairs of milk-molars in eachjaw ; those of the upper jaw having their crownsmore elonofated from front to back than is the casewith the premolars by which they are subsequentlyreplaced. As the colt grows older, the first molarcuts the gum before the last premolar has replacedthe corresponding milk-molar; and, as a conse-quence of this, it will always be found in an adulthorse that the crown of the first molar is rathermore worn than that of the tooth immediately in
Text Appearing After Image:
POSITION AND STRUCTURE OF HORSE 35 front of it, that is to say, the last premolar. Withthis exception, each cheek-tooth in an adult horseis always more worn than the tooth immediatelybehind it. With the exception of the first and last, whichare more or less pointed at the free end, an uppercheek-tooth of a horse consists of a square prismrather more than an inch in diameter, and aboutthree inches in height when unworn, with its lowerextremity terminating in four roots. Both theouter and inner surfaces are marked by strongvertical tlutings; and when in use, only a smallextent of the upper part of the crown is exposedabove the gum. As these teeth are usually seen in a more orless worn condition, it is preferable to take such apartially worn tooth as the basis for a description oftheir leading characteristics. Such a tooth may becompared in structure to the incisors ; its apparentcomplexity of structure being due to the pushing-in,on the summit of the crown, of two pits compar-able to th

Note About Images