4 THK IKATHKUKD TUl liES. 



The wi'll-kiuAvii l);iiu' called tlie meiTV-tliouolit, counteracts the tentleiU'V to approach 

 which the action of th(> wings produces iu flight. There are also clavicles, or collar- 

 bones, which are long and narrow, uniting at one end -with the srapi'/if, and at their 

 point oi' junction assist to form the cavity in which the head of the huinerus is r(>ceived. 



The inferior limbs consist of the following parts : — The thigh-bone, ov fcniiir (c), which 

 is short, lies close to the body, enveloped in muscles, covered ^^•ith tlie skin, and concealed 

 beneath the feathers. The next part is the tibia (d), and to this succeeds the farnna (e), 

 con.sisting of a single elongated bone, covered only with scaly skin, having the toes 

 articulated to its extremity. In most birds the toes (f) are three before and one behind, 

 but here great variety prevails. 



The nimiber of bones which compose each respective toe appears, iiidred, to be regulated 

 by a imiform law. The innermost toe, which may be compared to a thumb, consi-sts 

 invariably of two bones ; that \\hich is next to it in the order of sequence has always 

 tlnci' ; that which follows has four; and the outermost toe has five bones: the claws 

 being in every case affixed to the last juints, which have, therefore, been termed the 

 ungual bones. 



The perching birds have the two middle toes parallel to each other, and the inner and 

 outer toes turned back, so as to be opposed to them in action. They are thus enabled to 



FIG 3. 





lIAUM'.Oe. 



SKA-MF.W. 



PAuiiOQi rr. 



grasp objects with the greatest facilily, having, in fact, two fluunbs, whicii are opposable 

 to the two fingers. 



^^^len the bird is perched, it embraces the branch with its claws, and, by a \\'onderful 

 mechanism, it holds it the more .strongly the longer it is placed there. The flexible 

 muscles of the claws pass over the joints of the knee and the talons, and when those, 

 fatigued by the weight of the body, begin to bend, they draw over the tendons of the 

 muscles in (jiiestion ; then the claw bent by them seizes with greater force the branch 

 which sustains the bird. As to the birds with long claws, which generally keep on the 

 earth, they have been spared the fatigue of long standing, by pi'eventing the thigh from 

 liending over the leg ; when the member is extended, the lower part of the femur, which 

 j)resciits a IkjIIow, is rested on a projection of the tibia, like the bowl of a bilbocpiet on its 

 axis, and the animal, not wanting to contract its mu.sdes, experiences no weariness. 



When we proceed to the history of families, it will be seen that th(> disposition of the 

 claws is in harmony with the habits of the bird; thus walking birds, as the ostrich, 

 have long and strong claws and a small foot ; birds of prey, like the eagle, have the 

 claws short and vigorous, the nails crooked and .sharp; the birds which Hnc on tho 

 liaiiks of streams, and seek there for prey, have slender daws, but (excessively long, 

 and seem to be mounted on stilts ; ainong the birds which inhabit deep waters, the claws 

 are palinatcd, that is to say, between the parts a membrane is extended which does not 



