304 



therefore, that it is formed by a perichondria! ossificalion, for although 

 no ossifj'ing perichoiKlriiim is visible here, tiie fact that the bone is 

 formed from the surrounding mesenehyma co-ossifjing with carti- 

 lage, established the character of the ossification. In fig. 5 we give a 

 cross section of this first stage of the spina. 



I have not been able to recognize two centres of ossification in 

 the cartilaginous scapula, described by Rambaud and Renai.t (quoted 

 by PoiRiEK '), which, according to these authors, arise between the 

 40''' and 50''' day and fuse in the third month. 



In the scapula of an older embryo (56 mm. in length) this peri- 

 chondria! ossification appeals to be largely extended. The margo 

 anterior scapulae is almost reached. Tlie cartilage of the planum 





Fig. 6. Homo 56 mM. Transversal. 7l!( = Humerus; CZ = Clavicula; 

 Cor = Processus coracoideus; /4cr = Processus acromialis; 

 Sp =^ Spina scapulae; Sc = Scapula. 



scapulae, however, has been distinctly calcified over a considerable 

 area already. Tlie marked enlargement of tlie spina scapulae is shown 

 in fig. 6. Resides the spina this figure also shows part of the foramen 

 described above. The spina is formed by a growdi of bone between 



') PoiRiER el Gharpy, Traite d'Anatomie humaine. 



