288 HUMAN EMBRYOLOGY AND MORPHOLOGY. 



reaches the presternum. It may also contain another element. In 

 more primitive types of vertebrates, in fact in all below the higher 

 mammals, a part of the coracoid element of the shoulder girdle, 

 the epi-coracoid (pre-coracoid), is situated at the cephalic end of 

 the sternum (Kg. 244). The supra-sternal bones, not infrequently 

 seen on the upper border of the human manubrium sterni (Fig. 

 231), appear to represent the epi-coracoids. These bones are 

 probably always present, but their presence is difficult to detect 

 because they are commonly more or less completely fused with 

 the presternum (Paterson). Occasionally the first segment of the 

 meso-sternum joins the manubrium instead of the body of the 

 sternum — a union frequently seen in some anthropoids. 



The presternum is the first part of the sternum found in 

 ascending the scale of vertebrate animals, and is developed as a 

 median ventral support for the shoulder girdle. 



