RUMINANT UUADRUPEUS. 447 



the early periods of ossification, however, they each 

 consisted of two slender bones, lying close and 

 parallel to each other ; but afterwards united by an 

 ossific deposition, which fills up the interval be- 

 tween them, and leaves behind no trace of suture.* 

 In proportion as the young animal acquires strength, 

 the union of these two bones becomes still more 

 intimate, by the absorption of the partition which 

 separated their cavities ; so that ultimately they 

 constitute but one cylinder, with a single central 

 cavity, which is occupied by marrow. 



The cannon bone is much elongated, both in the 

 fore and hind extremity ; so that the carpus and 

 tarsus, which are the commencements of the real 

 feet, are raised considerably above the ground. It 

 is a common mistake, arising from the height of 

 these joints, and the names they bear in ordinary 

 language, to consider them as the knees of the 

 animal. The slightest inspection of the skeleton 

 will be sufficient to show that what is called the 

 knee in the fore leg is properly the wrist ; and in 

 the hind leg, the part so misnamed is really the 

 heel. Thus the foot, especially in the posterior 

 extremity, is of great length ; a structure which is 

 evidently intended to give greater velocity to the 

 actions of the muscles, while it at the same time 

 ensures the utmost steadiness and security of motion. 



At the lower extremity of the cannon bone there 

 are two articular surfaces, indicating the originally 

 separate ends of its two component bones. They 

 are for the articulation of the two following bones, 

 which are also very long, and which correspond in 



* The observations which establish this fact are detailed by G. 

 St. Hilaire, in a paper in the " Memoires du Museum," x. 173. 



