88 



THE BONES. 



In the Cat there are also eight bones. The second, or pyramidalis, of the tipper row 



is very developed ; it occupies all the external border of the carpus, and articulates with 



the ulna, the first bone of the second row, and the first metacarpal. The supercarpal 



bone, elongated, prismatic, and thickened at its extremities, offers in front two coalescing 



articular facets, one to correspond with the ulna, the other to join the pyramidalis. 



The bones of the inferior row decrease in thickness from the first to the fourth, and 



correspond : the first, to the first and second metacarpals ; the second, to the metacarpal 



of the third digit ; the third, to that of the fourih digit ; the 



Fig. 53. fourth, to the metacarpal of the thumb. 



In the Dog there are only seven bones, as the scaphoid 

 and semilunar bones are united, but the general disposition 

 is the same as that in the Cat. 



Lastly, in the Ox and tSheep the carpus is only composed 

 of six bones: four in the upper row, and only two in the 

 lower, where the os magnum and trapezoides are consolidated. 

 The supercarpal bone has no groove for gliding, and tfce 

 pyramidalis articulates with the radius and cubitus. The 

 bones of the lower row only articulate with the principal 

 metacarpal bone. (Professor Gobaux, in 1865, exhibited 

 specimens which go to prove that of the two bones of the 

 lower row in the carpus of Ruminants, the internal really 

 represents two; so that these animals actually have seven 

 carpal bones like the Horse.) 



2. Metacarpal bones. The number of metacarpal bones 

 varies much in the domesticated animals : 



In the Carnivora there are 5 



In the Pig there are ..*.... 4 

 In Ruminants there are 2 



The five metacarpals of the Dog and Cat articulate with 

 each other, at their superior extremities, by lateral facets; 

 they offer, at their inferior extremity, a'condyle prolonged 

 backwards by an articular surface resembling that of the 

 Horse. The middle two are always longer than the two 

 lateral. The smallest belongs to the fifth digit, or thumb, 

 and is terminated inferiorly by a trochlea. 



The four metacarpals of the Pig articulate with each other, 

 as in the Carnivora. The second and third are larger than the 

 first and fourth. The fifth metacarpal is not developed. 



In Ruminants the metacarpal bones are two in number : 

 a principal, which itself results from the consolidation of the 

 second and third metacarpals, and another altogether rudi- 

 meritary. 



The principal metacarpal is channeled on its anterior face, 

 and for its whole length, by a deep vascular fissure a trace 

 FORE-ARM AND FOOT OF o f the primitive separation of the bone in two pieces. This 

 THE DOG ; ANTERIOR nssure presents, interiorly, the anterior orifice of a canal that 

 FACE - completely traverses the bone. The posterior face is also 



1, First digit; 2, Second marked by a very slight longitudinal groove. The superior 

 digit; 3, Third digit; extremity exhibits, extern; illy and posteriorly, a single diar- 

 4, Fourth digit ; 5, throdial facet for the articulation of the rudimentary meta- 

 Thumb; 6, 7, 8, 9, First carpal. The inferior extremity is divided by a deep notch 

 second, third, and fourth into two articular surfaces, which together resemble the single 

 bones of the lower row surface in the Horse; each corresponds to one of the digits; 

 of carpal bones ; 10,11, the external is always smaller than the internal. In the 

 First and second bones foetus, the two long bones that form the great metacarpal 

 of the upper row; 12, are simply laid together, and their medullary canals are sepa- 

 Supercarpal bone ; 13, rated from each other by the double partition which results 

 Body of the ulna; 14, from this apposition ; after their coalescence, however, the par- 

 Apex of the olecranon ; titions are completely destroyed by resorption, and in a short 

 15, Beak of the olecra- time there is only a single medullary canal for the entire bone, 

 non; 16, Body of the The rudimentary metacarpal is only a small osseous stylet, 

 radius. articulating, by a diarthrodial facet, behind and to the outside 



of the superior extremity of the principal metacarpal ; it is 

 sometimes absent in the Sheep and Goat. 



