THE PIGEON l8l 



(2) Remove the muscles from both sides of the sternum 

 and expose the bones connecting it with the framework of 

 the body. Observe the union of these bones with the ster- 

 num. Is there a movable joint ? Is there anything between 

 the bones at their union ? What is it ? These are the cora- 

 coid bones, and they unite with the scapulae which run back 

 over the ribs. Do you find another bone present in front 

 of these? Note its shape, length and way of attachment. 

 What name is generally applied to it? It is the clavicle 

 which in other vertebrates forms a principal part of the 

 shoulder girdle, but in the bird it is not as highly devel- 

 oped as the coracoid bones. 



(3) Loosen the coracoid bones from the shoulder, cut 

 away the ribs from the side of the sternum and remove the 

 sternum, the coracoids and the clavicles. This exposes the 

 internal organs. With the scissors cut the skin up to the 

 throat and spread it out on the sides. 



II. The Vital Organs of the Visceral Cavity. — 

 ( I ) Beginning with the head, find the opening at the back 

 of the mouth. Loosen the sides of the jaw, note the esopha- 

 gus, and follow it down the neck, loosening it from the sur- 

 roundings organs as you proceed. Running along by the 

 side of the esophagus will be found the trachea, or wind- 

 pipe, which may be separated from the esophagus and 

 studied apart. 



(2) Is the esophagus the same size all the way down? 

 What is the object of the enlargement? What is it called? 

 What advantage does it give the bird ? How does the bird 

 swallow? Can it swallow with head down? Why? Tie 

 a string tightly around the esophagus, behind the crop, cut 

 the esophagus in front of the string, and remove it. Ex- 



