150 SKELETON OF THE DOG 



with a discoid sesamoid bone. The second and fifth are placed more on the pos- 

 terior aspect of the large l)ones than is the case in the fore limb. 



The first and second phalanges are a little longer and narrower than those of 

 the fore limb. 



SKELETON OF THE DOG 

 VERTEBRAL COLUMN 



The vertebral formula is CjTj3L7(g)S3Cy2Q_^3. 



The cervical vertebrae are relatively longer than in the ox and the pig. The 

 bodies of the typical vertebra diminish in length from first to last and are com- 

 pressed dorso-ventrally. The anterior extremity is moderately convex and the 

 posterior slightly concave; both are oblique. The median ridge and lateral grooves 

 on the upper surface of the body are very well marked. The second, third, and 

 fourth' have distinct ventral spines. The spinous process of the third has the 

 form of a long low crest; in the remainder it is higher, blunt-pointed, and inclined 

 forward. The transverse processes of the third, fourth, and fifth project downward 

 and backward, and divide into two branches; of these, the anterior one is thin, 

 and the posterior is thick and tuberculate at its free end. The process of the 

 sixth has two parts; one of these is an extensive quadrilateral plate directed down- 

 ward and outward and ridged on its inner surface; the other part is short and blunt, 

 and is directed outward and a little backward and upward. The seventh is readily 

 distinguished by its shortness, the length of its spine, and the single transverse 

 process. The posterior articular processes bear tubercles which are large on the 

 third, fourth, and fifth. 



The ventral arch of the atlas is narrow from before backward, and bears a 

 small tubercle posteriorly. The upper surface of the dorsal arch is strongly 

 convex and rough centrally. The wings are wide, flattened, and almost horizontal. 

 The upper surface is rough. There is an alar notch (Incisura alaris) on the anterior 

 border instead of the anterior foramen. The foramen transversarium is present. 



The l)ody of the axis is flattened dorso-ventrally, especially in front. The 

 odontoid process is rounded and relatively long, reaching almost to the occipital 

 bone; it is inclined upward a little. The articular surfaces which flank it are 

 condyloid in form and very oblique. The inferior surface is wide, and is divided 

 by a median crest into two fossae. The transverse processes are single, pointed, 

 directed backward and outward, and perforated by relatively large foramina 

 transversaria. The spinous process is thin and of moderate height, but very long; 

 it is prolonged forward so as to overhang the dorsal arch of the atlas, and is ter- 

 minated l)ehind by a tuberosity which is connected by two crests with the posterior 

 articular processes. The anterior notches are large and are never converted into 

 foramina. 



The ])odies of the thoracic vertebrae are wide and compressed dorso-ventrally, 

 especially at each end of the region. Their convex anterior surfaces are depressed 

 in the middle. The posterior facets for the heads of the ribs are absent on the 

 last three or four. The transverse processes resemble those of the horse. They 

 bear mammillary processes except at the anterior end of the region. The facets 

 for the tubercles of the ribs are large and concave in the anterior part of the series, 

 and become smaller and slightly convex further back. The last three have acces- 

 sory processes also. The first three or four spinous processes are about equal 

 in length. Behind this they become gradually shorter to the tenth, and then remain 

 equal. The backward slope is most marked in the ninth and tenth. The eleventh 

 is practically vertical (anticlinal vertebra) and the last two incline slightly forward. 



