106 INTRODUCTION TO ZOOLOGY. 



The Internal Structure. 



1. Insert a tube into the mouth and inflate the 

 crop. Carefully remove the skin and inflate again. 



2. Loosen the crop from the neck and breast. 



3. Find the windpipe, or trachea. Describe its 

 structure. 



4. On each side of the neck is a vein and a white 

 cord. The cord is the pneumogastric nerve. The 

 vein is the jugular vein. 



5. Insert the tube into the glottis and inflate the 

 lungs. Observe the swelling of the whole body, and 

 the inflation of the thin-walled air sac in front of the 

 breast bone. Other sacs can be seen just behind the 

 breast bone. 



6. Find the ridge of bone along the breast of the 

 pigeon. This is the keel of the sternum. 



7. Cut the large muscle of the breast loose from 

 the sternum. The muscle is the pectoralis major. 

 Loosen it all ai-ound except at the front end. Find 

 the white cord (tendon) by which it is attached in 

 front. To what is it attached? What motion is pro- 

 duced when the pectoralis major is pulled? 



8. Find the pectoralis minor, or subclavian mus- 

 cle, directly under the pectoralis major. Loosen it, 

 except in front. Trace the tendon to its insertion. 

 What motion is produced when the pectoralis minor 

 is pulled? 



9. Scrape the flesh from the breast bone and from 

 the bones in front. Find the wish bone. It consists 

 of the homologaes of two clavicles united. Remove 

 it and draw. 



10. Find the coracoid bones, extending from the 

 sternum to the shoulder. What is the vise of the cora- 

 coid bones and the clavicles ? 



11. Remove the sternum carefully, clean it, and 

 draw. 



