THE PIGEON 167 



behind and beneath the lungs and along the outer sides of the 

 abdominal sacs; they join the sides of the lungs. The anterior 

 thoracic sacs lie in front of and partly beneath the posterior 

 thoracic sacs; they join the ventral surface of the lungs. The 

 interclavicular sac is a branched structure which lies beneath the 

 anterior end of the breastbone and the clavicle; it joins each lung 

 just in front of the main bronchus ; on each side it is joined by an 

 axillary sac which lies beneath the shoulder. The paired cervi- 

 cal sacs lie in front of the lungs, with the anterior ends of which 

 they communicate. 



It is impossible to dissect out these sacs without destroying 

 the organs among which they lie. Some of them, however, can 

 easily be seen. Lay bare the humerus, the large bone in the upper 

 arm, and cut a hole in it. Insert the blowpipe in the glottis or in 

 a slit in the trachea, and blow into the lungs. The air will be felt 

 coming out of the humerus, which is a hollow bone containing 

 a branch of the axillary sac. 



Make a midventral incision through the abdominal wall from 

 the hinder end of the breastbone to the anus ; do this by lifting 

 up the wall with the forceps and cutting it with scissors. Make 

 a transverse incision on each side along the hinder end of the 

 breastbone and cut away the flaps of the abdominal wall. Inflate 

 the lungs again ; the abdominal sacs will be filled and brought 

 into view. Note the great delicacy of their walls. Under the 

 wings will be seen the axillary sacs, and beneath the crop the 

 interclavicular sac. 



The Viscera. Lay bare the breastbone, removing the pectoral 

 muscles from it. Cut the breastbone loose from its attachments 

 along its posterior and lateral margins. Lift it up gently and ob- 

 serve the falciform ligament,— a transparent, median mesentery 

 which joins it with the organs beneath. Note the large liver 

 beneath the hinder part of the breastbone. Cut the falciform 

 ligament and, still lifting up the breastbone, note the large heart, 

 which lies in its concave dorsal surface. Entirely remove the 

 breastbone from the body, cutting with scissors the ribs at its side 

 and the bones of the shoulder girdle, which join the breastbone with 

 the shoulder blade. Be careful to avoid cutting the blood vessels. 



