324 KANSAS UNIVERSITY SCIENCE BULLETIN. 



shaft of each prong, but at the base of the V, where we would 

 expect it if the scapula were a single element. The threads of 

 bony matter are seen running in both directions and along the 

 sides of each prong from the base of the V where they have 

 their origin. At the base of the V the fibers are most compact, 

 and here is the center of ossification for the scapula. In order 

 to be sure that the single condition was found in early embry- 

 onic life before ossification sets in, sections have been made 

 which show that there is no separation in the early stages of 

 the element, and that both prongs originate synchronously. 

 The fibers do not occur in the glenoid fossa but are present on 

 the inner side of the V. The glenoid cavity, as stated by 

 Rathke, remains cartilaginous. 



Rathke has obtained practically the same result in some 

 forms, and in others he secured results which would seem to be 

 contradictory. His final conclusion is that there are two 

 elements in the scapula, although he studied forms which 

 showed clearly but one ossific center. Hulke* has rather mis- 

 interpreted Rathke and converts the embryologist's language 

 into meaning that he had discovered two centers of ossification 

 for this bone. As a matter of fact, the fibers of bone when laid 

 down are very difficult to see in the early stages. Especially 

 would this be true in dissected specimens, and it is no 

 wonder that Rathke thought there were two in some and 

 one in others. That he did discover forms in which there was 

 but a single center is evident from the following: "In jedem 

 Stiicke aber geschiet dies'' nicht, ... an zwei Stellen, 

 sondern nur an einer, und zwar in der Nahe der Grube fur 

 das Schultergelenk . . ." Parker, working some sixteen 

 years later, came to the latter conclusion in regard to the 

 scapula, for he says, four years after his investigations : "This 

 front fork forms with the scapula a gentle arc; it is of the 

 same thickness, nearly the same length and has no separate 

 osseous center, the two bars being hardened by one ectosteal 

 sheath."i° Baur has called the anterior ray of the scapula 

 the "proscapula," but Andrews suggests that a better term 

 would be the proscapular process, since the former term im- 

 plies the existence of a separate element. 



There is no great similarity in the fundamental structure 



8. Hulke, 1893, Proc. Roy. Soc. Lond., p. 249. 



9. Rathke, 1848, Ent. Schild., p. 1.39. 



10. Parker, 1868, Structure of Shoulder Girdle, Ray Society, p. 141. 



