Teeth of Horses ']t^ 



least modified mammals, iu fact, have the radius aud ulna, 

 the tibia aud fibula, distinct and separate. They have five 

 distinct and complete digits on each foot, and no one of these 

 digits is very much larger than the rest. Moreover, in the 

 least modified mammals, the total number of the teeth is very 

 generally forty-four, while in the horse the usual number is 

 forty, and, in the absence of the canines, it may be reduced to 

 thirty-six ; the incisor teeth are devoid of the fold seen iu those 

 of the horse ; the grinders regularly diminish in size from the 

 middle of the series to its front end ; while their crowns are 

 short, early attain their full length, and exhibit simple ridges 

 or tubercles, in place of the complex foldings of the horse's 

 grinders. 



" Hence the general principles of the hypothesis of evolution 

 lead to the conclusion that the horse must have been derived 

 from some quadruped which possessed five complete digits on 

 each foot ; which had the bones of the forearm and of the leg 

 complete and separate ; and which possessed forty-four teeth, 

 among which the crown of the incisors and grinders had a 

 simple structure ; while the latter gradually increased in size 

 from before backwards, at any rate in the anterior part of the 

 series, aud had short crowns. 



" Aud if the horse had been thus evolved, and the remains 

 of the different stages of its evolution have been preserved, 

 they ought to present us with a series of forms in which the 

 number of the digits becomes reduced ; the bones of the fore- 

 arm and leg gradually take on the equine condition ; and the 

 form and arrangement of the teeth successively approximate 

 to those which obtain in existing horses. 



" Let us turn to the facts and see how far they fulfill these 

 requirements of the doctrine of evolution. 



" In Europe abundant remains of horses are found in the 

 Quaternary and later Tertiary strata as far as the Pliocene 

 formation. But these horses, which are so common in the 

 cave-deposits and in the gravel of Europe, are in all essential 

 respects like existing horses, and that is true of all the horses 

 of the later part of the Pliocene epoch. But, in the deposits 

 which belong to the earlier Pliocene, and later Miocene 

 epochs, and which occur in Britain, in France, in Germany, in 

 Greece, in India, we find animals which are extremely like 



