194 VERTEBRATE ZOOLOGY 



In down feathers either there is no shaft— the barbs arising 

 from the distal end of the quill— or the shaft is very rudimentary ; 

 no hooks are present. In the filoplumes either the barbs are absent 

 or they are present in a rudimentary condition. 



Exercise 35. Draw a down feather much enlarged. Draw a filoplume. 



The endoskeleton is the inner framework of the body and is 

 made up of bone and cartilage. It may be divided into (i) the 

 axial skeleton, which includes the skull and the vertebral column, 

 with the ribs and the sternum, and (2) the appendicular skeleton, 

 which forms the framework of the extremities. 



To prepare the internal skeleton for study, open the abdominal 

 cavity, without injuring any of the bones, and remove all the 

 viscera. The body should then be boiled a short time until the 

 skin and muscles can be easily removed. Do not boil it so long 

 that the skeleton falls apart. If the neck vertebrae show a tend- 

 ency to become separated from one another, they had better be 

 strung on a cord. The head should be removed from the neck, 

 and care taken not to lose the lower jaw or the hyoid apparatus, 

 which lies in the floor of the mouth and supports the tongue. 

 Care must be taken also that the bones of the legs and wings, 

 and of the uropygium, do not become separated. 



Observe the general character of the skeleton. It is distin- 

 guished by great lightness, almost all the bones being hollow or 

 spongy, instead of compact or filled with marrow. It is also dis- 

 tinguished by great rigidity, the bones having a decided tendency 

 to ankylose. 



The Appendicular Skeleton : the Anterior Extremities. These 

 consist of the pectoral girdle and the wings. The pectoral, or 

 shoulder, girdle is a strong structure which forms the connection 

 between the skeleton of the wings and the trunk; during flight 

 the body of the bird is supported in the air by the wings, and it 

 is important that this connection be a strong and yet an elastic 

 one. The girdle is composed of a right and a left half, which are 

 joined ventrally by the sternum, or breastbone. Each half con- 

 sists of three bones : the scapula, the clavicle, and the coracoid. 

 Of these bones the first named is dorsal in position ; the other two 



