THE POSTERIOR LIMBS. 



105 



Fig. 68. 



2. Bones of the Metatarsus. 



These bones are three in number, a median and two lateral, and offer the 

 greatest analogy to the metacarpal bones. This enables us to dispense with 

 a general description of them, and to confine ourselves only to indicating 

 the differential characters which distinguish them from the corresponding 

 bones in the anterior limb. 



The principal, or median metatarsal bone, is longer than the same 

 metacarpal, and its body, instead of being slightly compressed before and 

 behind, is nearly a regular cylinder. It presents out- 

 wardly a fissure which is directed at first obliquely 

 backwards and downwards, and afterwards descends 

 vertically along the lateral external metatarsal bone. 

 The articular surface of the superior extremity is ex- 

 cavated in its centre by a large fossa of insertion. The 

 inferior extremity is at the same time wider and thicker 

 than that of the metacarpus. 



Of the two rudimentary (digital) or lateral metatarsal 

 bones, the external is always longest and thickest. The 

 internal bears on the superior face of its head three 

 articular facets, two of which respond to the small 

 cuneiform, and the third to the large bone of that name. 



3. Bones of tlie Digital Region. 



The digital region of the posterior closely resembles 

 that of the anterior limb. The analogy in the con- 

 formation of these bones is even pushed so far, that 

 it becomes very difficult to distinguish them from one 

 another. 



It is remarked, nevertheless : 1, That the first pha- 

 lanx is not so long as in the anterior limb, and less 

 wide and thick at its inferior extremity, but is, on the 

 contrary, wider and thicker at its superior extremity ; 2, 

 That the lateral diameter of the second phalanx is 

 shorter ; 3, That the third phalanx, less spread out"j 

 towards its inferior border, has more the shape of a V, * f 



and that its inferior face is more concave ; 4, That the POSTERIOR ASPECT OF 

 sesamoids are less voluminous; 5, That the navicular LEFT METATARSUS. 

 bone is shorter and narrower. !> Head of principal 



metatarsal bone ; 2, 



3, External and in- 

 ternal splint bones, 

 or metatarsals of the 

 rudimentary digits; 



4, Rough surface for 

 insertion of suspen- 

 sory ligament ; 5, 

 Nutrient foramen ; 

 6, Middle ridge of 

 inferior articular 

 surface. 



DIFFERENTIAL CHARACTERS OF THE POSTERIOR LIMB IN 

 OTHER THAN SOLIPED ANIMALS. 



A. PELVIS. It is remarked : 1, That in all the domesticated 

 animals, with the exception of Solipeds, the direction of the coxae 

 is nearly horizontal ; 2, That in all, except Solipeds, the ilium 

 tends to assume a vertical direction ; 3, That in all the trans- 

 verse diameter of the pelvis is relatively less extensive. 



In the Ox, Sheep, and Goat, the space between the two coxae 

 is scarcely so great in front as behind ; the ilium is not volumi- 

 nous, and has only three processes on the superexternal iliac 

 spine. There is no furrow on the lower face of the pubis, and 

 its upper face, like that of the ischium, is very concave. Three eminences are seen on 

 the postero-external angle of the ischium. In early life, the ischio-pubic symphysis 

 shows an epiphysary nucleus in the middle of its inferior face. (The epiphysis on 

 the inner border of the ischium has been considered by some anatomists as an inde- 

 pendent bone, and described by them as the interischial bone.) 



