Branch Chordata 99 



appears to be a longitudinal opening in the roof of the 

 back part of the mouth.- Push a pin through the 

 nostrils from the outside. Where does its point enter 

 the mouth ? < 



IV. — Study the eyes and eyelids. How are the latter 

 attached ? See if you can find the nictitating mem- 

 brane which sometimes covers the eye of the living 

 bird. 



V. — Study the ear-opening. Describe its size and shape. 



VI. — Study the wings. How does their length compare 

 with that of the body .' How many joints in them ? 



VII. — Observe the kinds of feathers and their distribu- 

 tion over the body. Do you find on the trunk any 

 feather tracts beside comparatively bare places .'' Take 

 a long feather from wing or tail : see its central stem 

 or axis, and the vane which is made up of a vast num- 

 ber of barbs which in turn branch into barbules. The 

 barbules hold the barbs together. Are they more 

 effective toward the basal or the apical end of the 

 feather ? Compare a feather from the ear and one from 

 the breast with the long one. How do they differ .' 



VIII. — Study the legs : what bones should you think are 

 covered by the feathers .'' Is there any system in the 

 arrangement of the scales on the tarsus and toes .' 

 Notice the shape of the claws on the toes, and the pro- 

 tection along the under surface of the toes. 



INTERNAL ANATOMY 



IX. — Lay the specimen on its back in the dissecting 

 dish with its head pointing toward you. Cut the skin 

 along the median ventral line, beginning at the pos- 

 terior extremity of the lower mandible. Pushing back 



