AND PHYSIOLOGY. 97 



cula, merry thought, or wish bone. They also possess another 

 bone which acts the part of a clavicle, called the Coracoid. 

 It reaches from the scapula to the sternum, side by side with 

 the Furcula, and is a principal source of support to the 

 wings in flight. There is a bone analogous to this among 

 some reptiles. 



207. Humerus. — The Humerus is generally a % larger and 

 stouter bone than the femur, contrary to the relative propor- 

 tion in man. This is because the anterior extremities of birds 

 are of much more importance in their habits than the poste- 

 rior ones, since the hind legs in most of the flying birds act 

 merely as a support for the body when at rest, and are not of 

 special service for running or scratching. 



208. Bones of Wings, Fingers. — The two bones of the 

 fore-arm are proportionally longer than the same bones in 

 mammals, and are longest in birds of flight. The carpus is 

 represented by two short bones, and the metacarpus is of the 

 same number. In some birds the thumb is entirely wanting, 

 but when present it is made up of two bones. The little 

 finger has only one bone. The middle finger is the longest, 

 consisting of two and even three bones. 



209. Femur, Tarso-Metatarsus, — The Femur is both 

 thicker and shorter than the bones below it, which constitute 

 the leg. The Fibula is always, partially at least, united with 

 the tibia at its lower extremity. The Tarsal and Metatarsal 

 Bones are found as one, called the Tarso-Metatarsus, which 

 has at its lower extremity three pully-shaped heads for the 

 attachment of the toes. 



210. Sesamoid Bones. — Sesamoid Bones are abundant in 

 birds, and in many cases even the tendons themselves become 



Is this peculiar to birds alono ? 207. What is the comparative length and size of the 

 Humerus and Femur in birds ? Why are the anterior extremities in most cases the 

 longest ? 208. What is said of the two bones of the fore-arm ? How many bones are 

 there in the Carpus? Describe the fingers of birds. 209. What peculiarities in the 

 lower extremities of birds? Describe the Tarso Metatarsal Bone. 210. What is said 

 about Sesamoid Bones in birds ? 



