22 ANATOMY. 



these bones were larger than they are now, having the same length 

 and the same functional importance as the principal metacarpal 

 and metatarsal bones. The original ancestor of the horse is sup- 

 posed to have had five metacarpals and five metatarsals with cor- 

 responding digits or toes. 



Each digit contains three bones known as the phalanges, the 

 horse having three phalanges and the cow six. These are com- 

 monly known as the first, second and third phalanges, or os suf- 

 fraginis, os corona, and os pedis. The anatomy of this region 

 is discussed more fully in the special chapter on the foot. 



The phalanges, sesamoids, and navicular bones are very sim- 

 ilar to the corresponding bones of the front limb, already de- 

 scribed. 



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