THE STERNUM THE THORAX THE SKULL 131 



The neck is long, and forms (except in the posterior part of the series) a smaller 

 angle with the shaft than in the horse. The articular surface of the tubercle is 

 concave transversely, except on the last two or three, where the facet is small and 

 flat or absent. The ventral ends of the second to the tenth or eleventh inclusive 

 form diarthrodial joints with the costal cartilages. The first costal cartilages are 

 very short; they articulate by their medial surfaces with the sternum, but not with 

 each other. 



The presence of a fourteenth rib is not very rare. It is usually floating and may correspond 

 to an additional thoracic vertebra or to the first lumbar. Reduction of the thirteenth is more 

 common. The eighth cartilage often does not reach the sternum, but articulates with the seventh. 



THE STERNUM 



The sternum consists of seven sternebrse, most of which are developed from 

 two lateral centers. It is wider, flatter, and relatively longer than in the horse, 

 and the ventral crest or "keel" is absent. The manubrium is somewhat wedge- 

 shaped and laterally compressed. Its base forms a diarthrodial joint with the 

 body of the bone, and laterally it bears extensive facets for articulation with the 

 first pair of costal cartilages. The body widens from before backward, but behind 

 the last pair of costal facets it becomes much narrower. The ventral surface is 

 prominent on the second and third segments, concave further back. The lateral 

 borders are notched for the passage of vessels. The cariniform cartilage is absent. 

 The xiphoid cartilage is like that of the horse but is smaller. 



THE THORAX 



The bony thorax is shorter than in the horse. The inlet is higher. The roof 

 is short, and the floor is wider and relatively longer. The transverse diameter is 

 wider in the posterior part. The summits of the spinous processes are almost in a 

 straight line from the second thoracic vertebra to the middle of the lumbar region. 



The Skull 



Bones of the Cranium 



The occipital bone forms the lower part only of the posterior surface of the 

 skull, and is separated from the highest part (the frontal eminence) hy the parietal 

 and interparietal bones. The supraoccipital, interparietals, and parietals fuse 

 before birth or soon after, and the mass so formed is separated from the lateral 

 parts of the occipital bone by a transverse suture in the skull of the calf. Above 

 this suture is a central tuberosity, the external occipital protuberance, to which 

 the ligamentmn nuchae is attached, and the surface on either side is depressed and 

 rough for muscular attachment. There is commonly a median occipital crest 

 which extends ventrally from the protuberance. Below the suture the bone is 

 much wider than that of the horse. The foramen magnum is wide, so that the 

 condyles are further apart, except below. The paramastoid processes are short and 

 wide and are bent inward. Usually at least two foramina are found in the condy- 

 loid fossa; the ventral one is the hypoglossal, the other (often double) conducts a 

 vein from the condyloid canal.^ The latter passes upward from a foramen on the 

 medial side of the condyle and opens into the temporal canal. The mastoid for- 



^The number of foramina here is variable. In exceptional cases the foramen which opens 

 into the condyloid canal is very small or absent; much oftener there are two, and sometimes three. 

 In some cases there are two hypoglossal foramina. Thus as many as five foramina may be present 

 here. 



