THE AKTERWR LIMBS. 81 



with the semilunar and scaphoides; below, with tho principal metacarpal 

 and the internal rudimentary metacarpal. 



The third, or tr<i]n'z<ii(li>.<, tho smallest, is provided with five facets, and 

 is in contact with tho scaphoides above, and tho middle and internal meta- 

 carpals below. 



Collectively, these bones of the lower row form two Fig. 47. 



large, diarthrodial surfaces. The upper surface responds 

 to the bones of tho upper row, and is constituted in front, 

 and from without to within, by a small condyle and two 

 glenoid cavities ; behind, by two isolated condyles, 

 formed by the os magnum and the trapezoides. Tho 

 inferior articular surface is only formed by more or less 

 long and plane facets, which incline towards each other. 

 It corresponds to the three portions of the metacarpus. 



Sfrii'-tnri' and development. Each carpal bone is 

 formed by a nucleus of close spongy substance enveloped 

 in a layer of compact tissue. Each is developed from 

 a single centre of ossification. 



2. Metacarpal Bones. 



In Solipeds, the metacarpus is composed of three 

 bones, named the " metacarpals," standing parallel to each 

 other. These are the principal metacarpal and the two 

 rudimentary metacarpals, an external and internal. 



PRINCIPAL METACARPAL. This is a long cylindrical 

 bone, situated vertically between the carpus and tho 

 digital region. 



Body. The body is a little depressed before and 

 behind, a disposition which permits it to be described 

 as having two faces and two borders. The anterior face 

 is perfectly smooth and rounded from side to side. Tho 

 posterior face is flat, and exhibits : 1, Towards tho upper 

 third, the nutritive foramen of tho bone; 2, On the 

 sides, two narrow, roughened surfaces, parallel and elon- 

 gated vertically, commencing near the superior extremity 

 to disappi ar a little below the middle of the bone ; these 

 surfaces are held in apposition with tho rudimentary 

 mi tacarpals by means of an interosscous ligament which 

 is often ossified in old horses. The borders, external and 

 iiif- rnal, are very thick, round, and smooth, like tho an- 

 terior face. 



m i ties. Tho superior is flattened before and 

 behind, and presents : 1, Above, an undulating articu- 

 latory surface, formed by tho union of several flat 



x more or less inclined on one another: they 



ond to all the lower row of carpal hones; 2, An- 

 teriorly and inwardly, a tuberosity for muscular inser- 

 tion : 3, Posteriorly, and directly above the roughened 

 surfaces of the po>t--rior face, four small diarthrodial facets in pairs, and 

 running into the larger articular surface by their superior border: they are 

 adapted to similar facets on the rudimentary metacarpals. The i,,, 



,/////, elun^at'-d tran-\i TM ly. cm n sponds to the tir^t phalanx and tin- 

 large sesamoids by an articular surface, convex from ! fn to iM-hind, which 



a 



POSTERIOR VIEW OF 



Uli.lir MKTACAKri s. 



1, Head of large meta- 

 carpal bone for ar- 

 ticulation with the 

 trapi'/nMi-s, mag- 

 num, and uucit'onn : 

 2, Inner splint, or 

 Miiall metacarpal 

 bone, for articula- 

 tion with the trape- 



Ziii.lrs; 4, Sr:il>rous 



surface for tin- at- 

 tachment of the MI>- 

 pensory ligament ; 

 5, Nutrient fen- 

 IBM ; 'I. Median 

 ri'l^e separating tin- 

 two infi-ri'-r < "ii- 



