THE PIGEON 187 



to the coracoid, and freedom of motion. Note the wing 

 bones, radius and ulna, which are below the humerus. Ob- 

 serve their form, size, relation to one another. Note the 

 peculiar extension of the ulna back of the joint. Of what 

 advantage is this ? Below are found the carpus, metacarpus, 

 and phalanges, strangely modified into a hand in which the 

 phalanges are short and degenerated. 

 Draw bones of wing (Xi)- 



(3) The pelvic girdle may be studied in the same way. 

 The bones of the leg are femur, tibia, tarsometatarsus and 

 phalanges. Do you see any indication of a fibula? Can 

 you find the place of union of the tarsus and metatarsus 

 to form the tarsometatarsus? How are the phalanges ar- 

 ranged? Make a drawing of leg (X/4). 



The bones forming the pelvic girdle are: (a) the acetabu- 

 lum, which receives the head of the femur; (b) the ileiim, 

 which extends a considerable length before and behind the 

 acetabulum; (c) the ischium, projecting horizontally back- 

 ward from the acetabulum; (d) the pubis, which extends 

 downward and backward on the ischium. These bones are 

 very much modified to suit the peculiar structure and 

 habits of the bird. Study and explain the relation of the 

 habits of the bird to its structure. 



(4) The spinal column may next be studied, begin- 

 ning at the head. Sever the head from the first vertebra 

 of the neck, being careful not to injure the bones. Note 

 that the spinal column consists of four regions: (a) the 

 cervical vertebrae, sixteen in number ; (b) the thoracic, five 

 in number; (c) the sacrum, fourteen or fifteen vertebrae 

 fused together to support the ilium; (d) the caudal, four 

 or five free ones and a terminal pygostyle. 



