THE FOOT. 15 



depression called the nasal fossa ; they are often hid- 

 den by bristly or otherwise modified feathers. The 

 various forms which the bill assumes in different 

 groups of birds are indicated by terms, the meaning 

 of which is usually obvious. 



The Foot. Much misunderstanding prevails re- 

 specting the parts of a bird's legs and feet in compari- 

 son with those of a quadruped. Taking an ordinary 

 case, as that of a Robin for instance, that part of the 



FIG. 3. BONES OF A BIRD'S LEG AND FOOT. (From a Loon.) A, hip. B, knee. 

 C, heel, or ankle joint. D, bases of toes, a, thigh-bone (femur) ; A to B is the 

 thigh, or "second joint." A, knee-cap (patella), b, tibia', and c, fibula; these two 

 bones reaching from B to C, and representing the leg proper, or shin (crus). From 

 C to D only, that is, from heel to toes, is the foot proper, chjefly consisting, in a bird, 

 of the metatarsus , but in descriptive ornithology commonly called the tarsus ; in com- 

 mon parlance, the shank. The whole limb, down to C, is commonly buried in the feath- 

 ers ; beyond C is the naked part, d, metatarsal bone, consisting of three metatarsal 

 bones fused in one, commonly called the " tarsus." in, accessory metatarsal bone, sup- 

 porting i/, the first or hind toe, of two joints ; zt, second or inner front toe, of three 

 joints ; 3^, third or middle front toe, of four joints ; 4^, fourth or outer front toe, of 

 five joints. These joints are the phalanges. The dot-line i crosses the basal pha- 

 langes of all the toes ; dot-line 2, the next set of phalanges. (N.B. In the Loon, the 

 tibia projects above the knee-joint ; but such is the case in very few birds, the knee of 

 most birds being smoothly convex, as in man.) 



hinder limb which is both feathered and hidden in the 

 general plumage of the body, corresponds to the whole 



