THE ruHE-LIxMB. 



41 



on this bone towards the middle line (Figs. 32, 34), where it 

 widens out^ and is united by its external margin with the sternum, 

 thus forming the precoracoid as already described, see p. 40. 

 These connections are best seen in young animals, as is shown in 

 Fig. 34. 



The clavicle [ci) is of ossifying cartilage ; the cartilage (e), the 

 epicoracoid, is very large, and hyaline, and at cl runs directly into 

 the epicoracoids, which are here united mesially by ligament. In 

 the fully developed animal the whole of the epicoracoid changes to 

 calcified cartilage, as also does the precoracoid lying in the groove 

 of the clavicle. 



B. Bones of the Fore Limb. 



1. The arm has but one bone. 

 The humerus, os hmeri (Figs. 0^^, 36, 37). The shaft of the 

 humerus is, on the whole, cylindrical, the middle part being the 



Fig. 35- Fig. 36. Fig. 37. 



Humerus of Rana cs- 

 ciilenta, female, seen 

 from below. 



Humerus of Rana i:s- 

 culenta, male, seen 

 from below. 

 Figures twice natui-al size. 



Humerus of Rana 

 esculenta, female, 

 outer side. 



(• Anteiiur extremity. c' Posterior extremity. cd Crista deltoidea. 



cm Crista medialis. t trochlea. 



narrowest ; its dorsal surface is slightly concave, the ventral surface 

 convex. In the iipper half the cylindrical form is indistinct, from 

 the presence of a weJl-marked crest [crista âeltoidea) upon the under 

 or ventral surface. The hinder half of the bone has very different 



