OS METACARPI MAGNUM. 



77 



PISIFORM BONE.* 



The pisiform is a very small, pea-shaped bone, situated, when 

 present, 'at the postero-intemal part of the knee, in some cases 

 articulating with the trapezoid, and in others being imbedded in 

 the internal lateral ligament. It is generally, perhaps always, 

 present in old subjects, but often overlooked owing to its small 

 size. 



METACARPUS. 



The metacarpus, that part of the skeleton which lies between 

 the carpus and the finger, consists, in the horse, of three bones. 

 The principal one, the great metacarp?i bone, situated between 

 the others, which are called the inner and outer small meta- 

 carpals, is the only perfect one of the three ; the others are not 



D C B A 



Generic development of the Horse's foot. A. Foot of 

 Eohippus ; B, That of Orchippus ; C, That of Hipparion ; 

 D, That of Horse. The digits are numbered, when present, 

 I. to V. 



only small, but they have no distal articular surface, 

 frequently all three bones become united by ossification. 



Very 



OS METACARPI MAGNUM. 



(Fig. 17. 9.) 



The large metacarpal, or cannon bone, is a long, straight 

 bone, placed in i* vertical direction. This bone, one of the most 

 compact in the skeleton, is flattened in its shaft, from before back- 

 wards, especially towards its distal end, the anterior surface being 

 •convex and smooth, and the posterior broad, flattened, and pierced 



* [Some authorities call this bone the Trapezium, and our Trapezium the 

 Pisiform. Either view may be admissible, as the nomenclature will depend 

 upon whether we compare these bones analogously or homologously with those 

 ■of the human carpus. — Ed,, Second Edition.] 



