220 VERTEBRATES. 



barbs with the barbs of a contour feather. What is the 

 probable use of these down feathers ? 



There are certain hairlike feathers (filoplumes) on the 

 skin of birds. These are easily seen on a plucked fowl 

 before singeing. They are not hairs, as a microscopic 

 examination of one will prove. Birds do not have true 

 hairs. 



Other Structures. Separate the feathers above the 

 base of the tail, and find the oil can, a double, cone- 

 shaped gland, which secretes an oily fluid for "feather 

 dressing." The bird, with its beak, presses a drop of oil 

 from this gland, and distributes it over the tips of the 

 feathers, in the familiar act of preening. 



Examine the ear again, and note that the tympanic 

 membrane is at the bottom of a short external auditory 

 meatus, and that the skin of the head dips down into and 

 lines this opening. 



Holding the back of the head firmly with one hand, 

 alternately raise and depress the upper mandible, and 

 observe that it is movable upon the head. 



Within the mouth find the single guarded opening of 

 the nostrils. Find also the openings into the esophagus 

 and into the glottis. Note the shape and character of the 

 tongue. 



Insert a tube into the glottis, and inflate the lungs. 

 Note what portions of the body are expanded. 



Dissection. Prepare a freshly killed specimen for dis- 

 section. Fasten the specimen with tacks, back down- 

 ward, on a shingle, with legs and wings fully extended. 

 Part the feathers, and divide the skin along the median 

 ventral line, from the neck to the tail, taking care not to 

 cut through the thin abdominal muscles. Now loosen 

 the skin from the sides of the body by holding the 

 severed edge of the skin between a thumb and finger, 



