ORIGIN AND CHARACTERISTICS 35 



those of the wings, are composed of three prin- 

 cipal portions. The first of these is the Femur 

 or thigh, which, as we have already mentioned, 

 articulates with the cup or acetabulum of 

 the pelvis, following which come the Tibia 

 and Fibula, often more or less coalescent and 

 together forming the shank or '' drumstick," 

 and lastly the bones of the Foot. Not a little 

 confusion exists, even amongst persons fairly 

 familiar with birds, respecting these three divi- 

 sions of a bird's leg. The actual thigh of a 

 bird is hidden by the plumage, and the shank 

 (Tibia and Fibula) is often mistaken for it, as 

 the metatarsus is for the shank. The metatarsus 

 is a compound structure formed by the fusion 

 of the second, third and fourth metatarsal bones, 

 which when maturity is reached do not lie in 

 the same plane (except in the Penguins and 

 some Parrots), the third having its upper end 

 thrust backward and its lower end pushed 

 forward during the course of growth. The 

 fifth metatarsal is only seen in the embryotic 

 stage, soon disappearing, whilst the first meta- 

 tarsal chiefly remains separate, lying in the 

 majority of birds behind the distal part of the 

 others. The metatarsus is covered with a series 

 of angular horny plates or scutellae, varying 



