THE A.\Tl-:i;HHi I.IMHs. 



87 



uliui. li\ tlie pentadactylous animals, as Man, Iho Cut, etc., on 

 (fee contrary, this is a veritable long bone which equals, or.\.n 

 exceeds, the radius in volume. 



'1. The closeness of union betieeen the radinx anil ulna 'x in 

 i sed proportion as tJte animal exclusively i-mjilni/n UK i. 



tiling or trailing. Thus, in Solipeds and Itnini- 

 nants, and Pachyderms in general, the two bones are consolidated, 

 or at least united, by an interosseous ligament, and in so firm a 

 manner that they can only execute very obscure movements on 

 each other. The anterior limb of these animals is indeed only 

 used to support the body on the ground. In those, on the con- 

 tain, whicL m:iy employ it to dig up the soil, climb on tree*, < tv, 

 .>r as an organ of prehension, the radius and ulna are merely 

 joined nt their extremities by an articulation, which permits them 

 to move upon one another with the greatest facility. Kodents, the 

 majority of the Caruivora, and the quudrumana, are so provided; 

 but it is in Man that the relative independence of the two bones is 

 curried to the highest degree. No animal can so easily execute 

 the movements of pronation and supination of the hand, which 

 are d.-termined by the play of the two bones of the fore-arm on 

 each other. 



the indication of these fundamental characters may be 

 added s m,e details on a few particular and important points. 



In all the domesticated animals other than Solipeds, the ulna 



lojie 1 from three ossifying centres, extends the whole length 



of the radius, and concurs to form the articular surface correspond- 



ing to the carpal bones. It is an elongated bone in Ruminants, 



and a long bone, hollowed by a medullary canal, in the Pig and 



The inferior articular surface of the bone of the fore-arm in 

 II nut i Hants is cut obliquely from above to below, and from with- 

 out to within. In these animals we find the radius very flat from 

 to behind, the bicipital tuberosity scarcely noticeable, and 

 two radio-ulnar arcades united externally by a deep fissure. The 

 union of the two bones is more intimate than in the Horse, for the 

 ossification always finishes by invading that portion of the inter- 

 osseous ligament placed above the superior vascular arcade. 



In the Fig, the ulna is flattened from before to behind, and 



1 out on the posterior face of the radius, which it almost 



comjilt-i.-ly covers. Its olecranon is very prominent. In the Dog 



and ( 'nt. the two Ixmes of the fore-arm are nearly equal in volume, 



and are .-lightly crossed in an X fashion. The superior extremity 



ulna is ihieker than its lower extremity; it is nearly the 



in of this in the radius. Movable on one another, these 



only touch by their extremities, and to this effect offer : 1, 



AU>\e, (in die ulna, a concave articular surface, the small sig- 



inoid eavity, and on the radius a rounded hinge-like facet; '2, 



P> low, on the radius, a concave surface, and on the ulna a convex 



one. 



D. FORE-TOOT, OR HAND. 1. Carpal bones. The carpus of the 

 /'/:/ bke that of Man, contains eight bones four in each of the 

 The xecond bone of the upper row corresponds with the ulna, 

 and to a small extent with the radius. In the bones o! the lower 

 row, it is observed that the first corresponds with the two external 

 arpals, the second with the great internal m. taoXpal, the third 

 with the ] .receding and the small internal mrtnearpni. The fourth, 

 j. /.him. terminates inferiorly by a blunt point, and has no 

 is with the metacarpal bones, because the thumb is entirely 

 in this animal. 



Fig. 52. 



ranon; 2, Body of the ulna; 3, Body of the radio? ; 4. 



. siM.ni'l, .mil third bones of the upj>er row .>:' tin , n-pu- ; 7, 8, 



1-4 



.in.l second bones of the lower row ; 9, Kudiroentarv m.-t.i. .1- ' " > '"' 



pals; 10, Principal metacarpals: 11, External digit ; 1 : ., Intfi-a.d '" "ii ..\ : : 



\II.W. 



