46 THE SKELETON OF THE HORSE 
(Facies articularis tuberculi coste) for articulation with the transverse process of 
the corresponding thoracic vertebra. 
The sternal extremity (Extremitas sternalis) is slightly enlarged, and is united 
with the costal cartilage. 
The first rib is easily distinguished. It is shortest and the shaft widens greatly 
toward the sternal end. At the lower part of the anterior border there is a smooth 
Tubercle 
Costal groove 
Head Neck Tubercle 
Anterior border 
Anterior border 
Costo- 
chondral 
junction 
Sternal extremity Sternal extremity of costal cartilage 
Fic. 22.—Lerr Ercurs Rrp or Horse; Lat Fic. 23.—Ricur Ercarax Rie anp CosraL CARTILAGE OF 
ERAL VIEW. Horse; Mepiar Virw. 
impression where the brachial vein curves around it; above this there is commonly 
a small tubercle (Tubereulum sealeni) which indicates the lower limit of the in- 
sertion of the sealenus muscle. The costal groove is absent. The head is large and 
has two facets of unequal extent, which meet at an acute angle in front; the smaller 
one faces forward and articulates with the last cervical vertebra; the larger one is 
directed medially and articulates with the first thoracic vertebra. The neck is 
thick and very short. The tubercle is larger than that of any other rib and has an 
