BRANCH CHORD AT A; CLASS AYES: THE BIRDS 331 



keel-shaped bone with lateral expansions to which are 

 attached the ribs. Where are the largest and most 

 powerful muscles of the toad located ? Where are they 

 in the fish ? In the bird the most powerful muscles are 

 these pectoral muscles, which move the wings in flight. 



TECHNICAL NOTE. Cut the pectoral muscles from the left side 

 of the sternum, push hack and pin to one side. With a strong pair 

 of scissors cut through the ribs on the left side of the sternum and 

 through the overlying bones. Lift the whole sternum, with the 

 right pectoral muscle attached, to the left side of the pan and pin it 

 down. Cut through the membrane which covers the viscera and 

 cover the dissection with water. 



In this operation note the V-shaped wishbone in front 

 of the sternum. It is composed of the two clavicles with 

 their inner ends fused. Note the stout coracoid bones 

 extending from the anterior end of the sternum to the 

 shoulder. 



Note near the middle of the body the heart with the 

 large blood-vessels proceeding from it. Behind the heart 

 lies the large reddish-brown liver, and on the left side 

 below the liver is the large gizzard or muscular stomach. 

 Note the viscera folded over themselves in the body- 

 cavity. Push them temporarily aside and note in the 

 dorsal region under the heart large pinkish spongy sacs, 

 the lungs. These are attached by short tubes, the 

 bronchi, to the long cartilaginous trachea. At the union 

 of the bronchi with the trachea is a small expansion with 

 cartilaginous walls, w r ithin which are stretched small bands 

 of muscles. This organ is the syrinx, the song- or voice- 

 apparatus of the bird. It should be cut open and carefully 

 examined. Trace the trachea fonvard to its anterior end. 

 It opens by a glottis into the larynx, a slightly swollen 

 chamber with cartilaginous walls. Note the U-shaped 

 hyoid bone surrounding the front of the glottis. Through 

 a blowpipe or quill inserted into the glottis blow air into 

 the .trachea and observe the inflation of the lungs and of 



