Muscular Svstciii. 



The largest pectoral muscle (pectoralis major) arises from 

 the sternum and its keel, and from the clavicle ; is inserted 

 on the humerus ; and depresses the wing. The smaller but 

 longer muscle (pectoralis minor), exposed \Yhen the large 

 one is reflected, elevates the wing. It arises from the keel 

 and sides of the sternum, and is continued over the shoulder 

 to its insertion on the dorsal surface of the humerus. Aris- 

 ing chicHy from the coracoid, but in part from the sternum, 

 and inserted on the humerus is a small coraco-brachialis 

 which helps a little in raising the wing. 'I'here are sexeral 

 yet smaller muscles. 



Intoiostiiii; :\lso is the nioch:\nisni of peichiiiL;. 

 on ils jx'ich, the loos clasp Ihis tii:;hll)'. The 



When tlio binl sits 

 .'\or tendons ol' tlte 

 the luelixtarsal joint 



toes ate contiimod np\\ai\is in tlexor nuisoles o\e 

 to tlie tibia, and are llexei-1 atitoniatieal!)' when the lei:; is bent dur- 

 ing perehini^. Furthermore, an anibiens niiisele, inserted on the iVont 

 o{ the pubis, is continued down the anterior side of the t'ennir, and ils 

 lenLJon bending round the knee to the opposite sivie o{ tlie tibia, is 

 iirferiorly connected \\ith the Itexors of t\\'o digits. \Mien tiie leg is 

 bent in sitting, the anibiens tendon is stretched, and tlie digits clasp the 

 biancli. Thus the bin!, \\ hen asleep, does not fall I'tV its pcrcli. 



In connection with the muscular s\stem, we luay also 

 notice that the walls of the gizzard consist of thick muscles 

 radiating around tendinous discs. Two small sterno- 

 tracheal muscles ascend from sternutii to trachea. Complex 

 muscles are associated with the song-bo\. 



Skch-toii. 



In Birds there is a marked tendency to fusion of bones, 

 as seen in the skull, vertebral column, pelvis, and limbs. 

 In the (ligcon most of the bones, except those of the tail, 

 fore-artu, hand, and hind-limb, contaiti air spaces. 



The \ertcbral column is dixided into the regions — cer- 

 \ical, thoracic, lumbar, sacral, and caudal. In the pigeon the 

 mobile neck consists of fourteen cervical \ertcbra: with 

 cervical ribs, short except in the last two, which have 

 them well-developed. C">f the thoracic \crtebrx, namely 

 those whose ribs reach the sternum, the anterior four are 

 fused to one another, while the tilth is fused to the sacral 



