Aves. 117 



its inner surface ; separate it from a smaller muscle lying 

 under it, which will be known by the glistening appearance 

 of the muscle sheath ; sever the attachment of the pectoralis 

 major to the breastbone, and all other organs except at the 

 extreme front end ; here the muscle narrows into a tough 

 white cord, or tendon ; trace this tendon to its attachment to the 

 bone of the arm ; now lay the pigeon on its back in one hand, 

 and pull this muscle backward, noting the effect on the wing. 

 In like manner loosen all the posterior attachments of the sub- 

 clavian muscle which was covered by the pectoralis major, 

 lying in the angle between the keel of the breastbone and the 

 body of the breastbone ; prove its action, this time holding the 

 pigeon right side up. Compare these two muscles in size, and 

 in the amount of work they have to do. The hinder attachment 

 of each of these muscles is called its origin ; and the place of 

 attachment of the tendon to the wing bone is the insertion. Cut 

 through the body wall around the margin of the breastbone, 

 through the ribs, coracoid bones, and wishbone, and entirely 

 remove the breastbone. 



10. Covering a considerable part of the abdominal organs is 

 the reddish brown liver. 



11. Lift the liver and disclose, at the left of the body cavity, 

 a hard mass, the gizzard. Slit the abdominal wall in the middle 

 line back to the anus, push aside any fat that may cover the. in- 

 ternal organs, and turn the gizzard to the left of the bird to find 

 where the intestine arises from it ; trace the intestine from the 

 gizzard backward. 



12. The part of the intestine nearest to the gizzard is the 

 duodenum. 



13. In a long loop formed by the duodenum is a pinkish 

 organ, the pancreas. 



14. Trace the intestine, tearing away the fat and the thin 

 walls of the abdominal air sacs, observing that it is held in place 

 by a thin, transparent membrane, the mesentery. 



15. The intestine has two short side branches, the ceca. 



