222 VERTEBRATES. 



Dissect these breast muscles free from all attachments 

 except their insertions, and, while doing so, look for 

 veins, arteries, and nerves, entering the muscles near the 

 shoulder. 



The removal of the pectoral muscles discloses the enor- 

 mously developed sternum, with its sharp keel and its 

 lateral ribs. The V-shaped bone in front of the sternum 

 is the wiskbone or merrythought, and is made up of the 

 two clavicles grown solidly together at their inner ends. 

 The paired stout bones extending from the shoulders 

 to articulate with the anterior end of the sternum are 

 the coracoids. Disarticulate and entirely remove the 

 clavicles. Free the coracoids from the sternum, and turn 

 them outward. With small scissors cut away the exposed 

 abdominal wall, and cut forward through the ribs at the 

 sides of the sternum. Then remove the sternum, avoiding 

 blood vessels as much as possible. This will expose the 

 internal organs. Again inflate the lungs through the glot- 

 tis, and observe the large air sacs in the abdomen, commu- 

 nicating with them. Remove blood, which may collect 

 about the organs, with a small damp sponge. Moisten the 

 neck, if it dries and hardens too rapidly. 



II. The Trachea. Find at the base of the tongue a 

 small U-shaped hyoid lone surrounding the front of the 

 glottis, the long arms of the U extending posteriorly 

 behind the skull. Dissect it and the tongue free from 

 their attachments to the lower jaw. The glottis opens 

 into a slightly swollen cartilaginous antechamber of the 

 trachea, called the larynx. At the posterior end of the 

 trachea, where it divides into two small bronchi, is another 

 slightly swollen portion (the syrinx). This latter is the 

 principal voice organ in birds. Cut across the trachea 

 half an inch in front of the bronchi into which it divides. 

 Make a lateral cut with fine scissors along the sides of 

 the trachea and bronchi, and turn down the ventral wall. 



