BIRDS. 371 



The station of birds, the support of their body by the hind 

 limbs, is favoured by the flexures of the joints, by the thigla-bone 

 bent forwards, and the tarsus also directed forward, as also by the 

 long toes standing far apart. The flexure of the toes in grasping 

 branches is effected in many birds, involuntarily and even during 

 sleep, by the weight of the body, which bends the knee-joint. A 

 muscle, which runs from the pubic bone along the inside of the 

 thigh-bone [musculus gracilis s. rectus interims), goes with its long- 

 thin tendon over the knee-joint outwards, and is attached to the 

 upper extremity of the perforating flexor of the toes. The running 

 of birds is in many small singing birds rather a hopping; in the 

 struthious birds their rapid course is assisted by the stroke of their 

 wings. Some birds are peculiarly adapted for swimming, others 

 for climbing; but a certain law of compensation prevails in these 

 different motions, so that aptness in one kind is coupled with less 

 ability in the others. The most common, the chief motion is how- 

 ever flying ; as in swimming the feet expand their swimming-mem- 

 brane, and the toes are separated from each other whilst they are 

 extended backwards, and in the succeeding forward movement are 

 folded together and cleave through the water with the least ex- 

 posure of surface, so also in flying the wings are spread out so as 

 to act upon a large surface of air in their down stroke, and are 

 again folded up when rapidly brought forward. The bird flies to 

 the right or left, in the flrst case by moving the left wing more, in 

 the second the rights The motion of flying is uncommonly rapid 

 when compared with the motions of other animals. There are some 

 birds that can fly over more than 60 feet in a second. The velocity 

 of the swiftest race-horse is only about 40 feet in a second, and if 

 some can perform more, they are able to support such velocity 

 only for a short time. It is related that a falcon of the French king 

 Henry II. flew in one day from Fontainebleau to the island Malta^. 



The intelligence of birds is more highly developed than that of 

 reptiles. Their memory is testified by their capacity of learning. 



^ Such, long ago, was the statement of Borelli De Mot it Animalium, 

 Comitum, 1743, 4to, pp. 196, 197; but Borelli held greatly exaggerated ideas 

 respecting the muscular power of birds, which were refuted principally by J. J. 

 Prechtl in his Untersnchunr/en ilher den Flug cler Vogel, Wien, 1846, 8vo. 



2 BuFFON Hlsf. nat. des Oiseanx, i. Paris, 1770, 4to, p. 3?. 



24—2 



