THE PIGEON. Ill 



the windpipe and out of the humerus, and vice 

 versa. 



8. Slit the skin back over the abdomen to the anus, 

 loosen it well back on each side, and cut through 

 the abdominal wall just behind the breastbone ; in- 

 flate once more, and observe the abdominal air-sacs. 



9. Cut down into the muscle of the breast, close along- 

 side the ridge (keel) of the breastbone, and around 

 the outer border of the breastbone ; thus loosen and 

 raise a great flap of muscle, the pectoral is major. 

 Note the nerve and blood-vessels entering 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 attach- 

 ments of the muscle which was covered by the pec- 

 toralis 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 smaller muscle is the 

 pectoralis minor. 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 



