Fore Limb of Fowl. 105 



and ulna; of a number of small bones and cartilages (to be 

 more particularly described immediately), the carpus ; of a set 

 of longish bones, one for each finger, the metacarpals ; and, 

 finally, of a number of smaller elements, still several to each 

 finger, the phalanges. 



Of separate carpal bones, six can be recognized in, the 

 common frog. They are arranged in two rows, a proximal 

 and a distal. In the proximal row are three bones, of which 

 two articulate with the radio-ulna. The innermost of these is 

 the ulnare, the outermost the centrale. A litde below the 

 latter, but really belonging to the radius, is the radiale. In 

 most animals this bone is articulated with the radius; but in 

 the frog it has lost this primitive position. The distal row has 

 also three bones. The first of these bears the rudimentary 

 thumb, but also articulates with the second digit ; the second 

 articulates with the second digit only ; the third is much larger, 

 and is really formed by a fusion of two separate cartilages 

 belonging to the two next digits of the hand."- 



The shoulder-girdle and fore-limb of the Fowl differs 

 greatly from that of the frog — a difference which is, of course, 

 related to its very different use. 



The scapula is a thin scimitar-shaped bone, which lies along 

 the ribs, parallel to the long axis of the body. Below the 

 glenoid cavity, for the articulation of the humerus, is the cora- 

 coid, a more solid and a shorter bone than the scapula. From 

 the inner face of each coracoid a process grows forward, which 

 is a T(i.iasae.rAa.'rj procoracoid. The two coracoids are implanted 

 in grooves upon the anterior edge of the sternum. The clavicles 

 are represented by a curved and U-shaped bone often termed 

 the " furcula." It is a membrane bone, as is the clavicle of 

 the frog. 



The sternum of the fowl is a much more solid structure 

 than that of the frog. It grows out below into a thin but 

 strong keel, or carina, which serves for the attachment of the 

 powerful pectoral muscles, which are the chief agents in the 

 downward stroke of the wing during flight. This sternum is 



' It is apparently very rarely the case among frogs Ihat the fifth carpal 

 has a cartilaginous rudiment. 



