ANCESTRY OF THE HORSE. 319 



that the position of every footprint can ever be accurately 

 defined. 



We learn from the study of geology that living creatures 

 began to inhabit the earth after its crust, which was once in a 

 liquid state, had cooled down, and the action of physical 

 causes, such as wind and water, had commenced to form 

 sedimentary rocks, in which the bones and other remains of 

 existing animals, became entombed as fossils. Thus, through 

 countless ages, a history of animal and also of vegetable life 

 has been written in stone by the hand of time. The last leaves 

 of this book lie uppermost, while the first ones repose on fused 

 rock, of which granite is a familiar example. This history is 

 divided by scientific men into the Primary, Secondary, and 

 Tertiary periods, of which the last-mentioned is the only one I 

 shall take into account ; as, during it, hoofed animals appeared 

 for the first time on the earth. The Tertiary period is divided 

 into the Eocene, Miocene, Pliocene, and Pleistocene periods ; 

 the Eocene being the most ancient ; and the Pleistocene the 

 one immediately preceding historic times. In searching 

 through the records of the past, an examination of fossil feet 

 is particularly interesting ; for we can obtain from it the most 

 direct and the most clearly expressed evidence respecting 

 the capacity of movement possessed by the animals which, 

 during life, walked on the earth. 



Before beginning, I may remind my readers that the knee 

 of the horse corresponds to our wrist (see p. 32) ; and his 

 fore fetlock to the row of knuckles nearest to the wrist. 

 Instead of having, as in our hand, five metacarpal bones 

 between the knee and fetlock, he has only one entire bone 

 (the cannon-bone), and two rudimentary (or splint) bones. I 

 may remark that in the hind limb, the bones between the 



