STRUCTURE OF BIRDS. 37 



7. Above and before the pectoralis minor is a small muscle, 

 which arises from the upper part of the coracoid bone, and a 

 strong fascia extended from its base to its extremity above, passes 

 obliquely upwards, and is inserted anteriorly to the pectoralis 

 minor. Its action is to draw the humerus directly downwards. 



The muscles which arise from the scapula to be inserted into 

 the humerus, are the following : 



8. The siipra-spinatus^ Fig. 1, arises from the fore part of the 

 scapula, and is inserted into the posterior or inner crest of the 

 humerus externally of the tendon of the pectoralis minor. 



9. The infraspinatus arises from the outer surface of the 

 scapula as far as its extremity, and is inserted into the same 

 prominence as the last. These two muscles draw the humerus 

 backward. 



The suhscapularis arises from the fore part of the inner or 

 under surface of the scapula, and is inserted into the same pro- 

 tuberance. 



10. The deltoides arises from the fore part of the scapula, 

 and from the top of the coracoid bone, its anterior fibres being 

 in contact with those of the pectoralis major. Its anterior por- 

 tion is inserted into the outer and back part of the edge of the 

 anterior crest of the humerus, its posterior into that bone as far 

 as the origin of the supinator radii longus, that is, for four-fifths 

 of its length. A thin flap is attached to the skin in the bend 

 of the winsr. The deltoid muscle raises the humerus. 



Under the deltoid is the coraco-brackialis, which arises from 

 the tip of the coracoid bone and adjoining part of the scapula, 

 and is inserted into the proximal part of the crest of the humerus. 

 Its action is to pull the humerus forward and upward. 



The muscles inserted into the cubitus or fore-arm come next 

 in order ; but it may be proper here to describe a very curious 

 apparatus existing in the bend of the wing, anteriorly, between 

 the shoulder and wrist joints, b and d. At that part the edge of 

 the wing is formed by a fold of the skin enclosing an elastic 

 substance, and edged with an elastic tendon or fibre, which has 

 at its commencement at the shoulder joint a small muscle de- 

 tached from the pectoralis major. 



11. This muscle, named the tensor pUcw alw^ or stretcher of 



