156 SKELETON OF THE SHEEP 



The large metatarsal bone is usually regarded as consisting of the fused third and fourth 

 metatarsal bones, and the small bone as the second metatarsal. The meduDaxy cavity is subdivided 

 like that of the large metacarpal bone. Some anatomists, however, consider that the ridges at 

 the upper end of each border represent the second and fifth metatarsals (Rosenberg and Retterer) . 

 On this basis the small bone would be the first metatarsal. 



The phalanges and sesamoids resemble those of the thoracic hmb so closely 

 as to render separate description unnecessary. 



SKELETON OF THE SHEEP 



VERTEBRAL COLUMN 



The vertebral formula may be given as C'7Ti3L6-7S4Cyi6-i8, but it should be 

 noted that, except in the cervical region, variation in number is common. 



It is not very rare to find twelve thoracic and seven lumbar, or an ambiguous intermediate 

 vertebra. More commonly there are seven lumbar vertebrae without reduction in the thoracic 

 region. In some cases there are foiu-teen thoracic and five or six lumbar vi'rtebrEe, and Lesbre 

 records a case in wliich twelve thoracic and seven lumbar were present. In some cases the fourth 

 sacral vertebra remains separate, and in others the first coccygeal unites with the sacrum, although 

 the fusion here is rarely complete. Nathusius states that the number of coccygeal vertebrse 

 varies from three to twenty-four or more. 



The cervical vertebrae are relativelj^ longer than those of the ox. The atlas 

 differs chiefly in that the prominence on the dorsal arch is much less developed. 

 The anterior articular cavities are often separated by a central ridge. The wings 

 are produced to form blunt points behind. The spinous process of the axis is not 

 enlarged posteriorly; those of the succeeding vertebrse are less developed than in 

 the ox; they increase in length from the third to the last. The ventral spines are 

 rudimentary. The arches are separated dorsally by interarcuate spaces. 



The thoracic vertebrae are usually thirteen in number, but fourteen may be 

 present, or, more rarely, only twelve. Their bodies are relatively wider and less 

 constricted than those of the ox, and their extremities are not so strongly curved, 

 especially toward the end of the series. The intervertebral foramina are larger, in 

 correlation with the absence of the foramina which usually occur in the arches of 

 these vertebrge in the ox. 



The lumbar vertebrae number six or seven, the former being a little more fre- 

 quent than the latter. It is not common to find the nmnber reduced to five. In 

 some cases there is an ambiguous vertebra at the junction of the thoracic and lum- 

 bar regions. The bodies are more flattened dorso-ventrally than those of the ox; 

 their anterior ends are somewhat concave transversely, and the posterior ends are 

 almost flat. The anterior articular processes are strongly curved and overlap the 

 posterior ones. The transverse processes curve forward and have expanded ends. 



The sacrum consists orchnarily of foiu- segments, but the last vertebra may re- 

 main separate or undergo only partial fusion. There is no vascular groove on the 

 pelvic surface. The spines are not fused, with the exception of the first and second, 

 which may be partially united. The transverse processes of the last segment are 

 distinct and outstanding. 



The coccygeal vertebrae vary in number from three (in short-tailed sheep) to 

 twenty-four or more. The bodies have no hemal processes on the ventral surface. 

 The transverse processes are long and thin and project backward. 



THE RIBS 



The ribs usually number thirteen pairs, l)ut the occurrence of fourteen pairs is 

 not at all uncommon. The thirteenth rib is fioating and has a cartilage about an 



