BONES OF THE THORACIC LIMB 127 



The sphenoidal sinus is almost entirely in the sphenoid bone and does not 

 communicate with the palatine and maxillary sinus. It has one or two openings 

 into the ventral ethmoidal meatuses. There is no cavity in the perpendicular part 

 of the palate bone. 



There are several small air-cavities between the lateral mass of the ethmoid 

 and the anterior part of the frontal sinus, which communicate separately with 

 ethmoidal meatuses. 



BONES OF THE THORACIC LIMB 



The scapula is more regularly triangular than in the horse, relatively wider at 

 the vertebral end and narrower at the lower end. The scapular index is about 

 1 : 0.6. The spine is more prominent and is placed further forward, so that the 

 supraspinous fossa is narrow and does not extend to the lower part of the bone. 

 The spine is sinuous, bent backward in its middle, forward below. Its free border 

 is somewhat thickened in its middle, but bears no distinct tubercle. Instead of 

 subsiding below as in the horse the spine becomes a little more prominent, and is 

 prolonged by a pointed projection, the acromion, from which part of the deltoid 

 muscle arises. The subscapular fossa is shallow. The areas for the attachment 

 of the serratus muscle are not very distinct. The nutrient foramen is usually in 

 the lower third of the posterior border. The glenoid cavity is almost circular and 

 without any distinct notch. The tuberosity is small and close to the glenoid 

 cavity. The coracoid process is short and rounded. The cartilage resembles 

 that of the horse. 



The humerus has a shallow musculo-spiral groove. The deltoid tuberosity 

 is less prominent than in the horse, and the curved line running from it to the neck 

 bears a well-marked tubercle on its upper part. The nutrient foramen is usually 

 in the lower third of the posterior surface. The external tuberosity is very large, 

 and rises an inch or more (ca. 3 cm.) above the level of the head. Its anterior part 

 curves inward over the bicipital groove, and below it externally there is a promi- 

 nent circular rough area for the insertion of the tendon of the supraspinatus. The 

 anterior part of the internal tuberosity has a small projection which curves over 

 the groove. The groove is undivided. The distal articular surface is decidedly 

 oblique, and the grooves and ridge are very well marked. The coronoid and 

 olecranon fossae are deep and wide. The external condyloid crest is represented by 

 a rough raised area. The proximal end unites with the shaft at three and one-half 

 to four years, and the distal at about one and one-half years. 



The radius is short and relatively broad. It is somewhat oblique, the lower 

 end being nearer the median plane than the upper. The curvature is more pro- 

 nounced below than above. The shaft is prismatic in its middle part and has 

 anterior, external, and posterior faces. There is a marked increase in width and 

 thickness below. The proximal articular surface presents a synovial fossa which 

 extends inward from the deep groove between the two glenoid cavities. The 

 bicipital tuberosity is represented by a slightly elevated rough area. The posterior 

 facets for the ulna are larger than in the horse. The two bones commonly fuse 

 above the proximal interosseous space and always fuse below it, except near the 

 distal end, where there is a small distal interosseous space. A groove connects 

 the two spaces externally. The distal extremity is large, and is thickest internally. 

 Its articular surface is oblique in two directions, i. e., from within upward and 

 backward. The grooves for the extensor tendons are shallow. The proximal end 

 unites with the shaft at one to one and one-half years, and the distal at three and 

 one-half to four years. 



The approximation of the lower ends of the forearms and the carpi gives the "knock-kneed" 

 appearance in cattle. The obliquity of the joint surfaces produces lateral deviation of the lower 



