38 



THE BONES AND JOINTS. 



concentrically with the margin. The anterior border (f/) is bent 

 on itself so as to form a g-roove (Fig-. 27). The dorsal surface 

 of this bony plate is quite smooth^ and covered only by periosteum ; 

 the ventral surface, on the contrary, is for the most part covered 



Fm. 26. 



Fiii". 2: 



Suprascapula of Rana esctilnita, from above, 



twice nat. size. 

 Calcified cartilage. 

 Hyaline cartûage. 

 Bony portion. 

 Anterior curved border. 



Suprascapula of Rana csmknta, from below, 

 twice nat. size. 

 CO Calcified cartilage. 

 Co' Layer of calcified cartilage on the under siirface 



of the bone. 

 h Hyaline cartUage. 

 Bony poition. 

 0' Anterior curved border. 



by an even layer of calcified cartilage (Fig-. 27 co'). This passes 

 directly into the second portion of calcified cartilage (co) ; so that if 

 the whole be dried, the thin hard lamina of bone can easily be split 

 away from the underlying parchment-lils e cartilage. The layer of 

 calcified cartilage is, however, not so complete that the mprascaimla 

 can be said to consist of calcified cartilage. 



b. The scapula (Figs. 25*, 28, 29) is a long, flat, four-cornered 

 plate of compact bone, contracted in the middle, and wider at either 

 end. From above (Fig. 28 /) it descends to the shoulder- joint with a 



Fig. 28. 



Fig. 29. 



Left scapula of Rana esoiknta, 

 from below, twice nat, size. 



a Anterior border. 

 CM. Cavitas artkiilaris. 

 I Outer border. 

 m Inner border. 

 /( Posterior border. 



Scapula seen 

 from behind, 

 twice nat. size. 



f.(7. ('(iv. artkidaris. 

 d Dorsal i)roue.ss. 

 V Ventnil process. 



slight curvature, with the con- 

 vexity directed outwards. The 

 inferior or ventral border (Fig. 

 28 w), which assists in the forma- 

 tion of the shoulder -joint, is cleft 

 into two processes, a ventral and 

 a dorsal. This may be best seen 

 by looking at the border of the 

 bone from behind or before (as 

 in Fig. 29). The lower ventral 

 process (Fig. 29 v) may be re- 

 garded as the acromion, or at 



