68 INTRODUCTION. 



vertebrae have but little motion; the sternum is of great extent, 

 and still further augmented by a projecting blade, resembling 

 a keel. The sternal as well as the vertebral part of the ribs 

 is bony; in this part of the trunk every thing is disposed, so as 

 to give a solid support and muscular attachments to the wings. 

 The shoulders are formed by the merry thought, (the four- 

 chette) the ossa coracokles, which are very strong, and by elon- 

 gated and feeble scapulae. The wing is supported by the hu- 

 merus, the two bones of the fore-arm and the hand, which is 

 lengthened and has a finger, and two others that are rudimental; 

 it has a range of elastic quills. The pelvis, which is very long, 

 furnish insertions for the muscles of the inferior members, and 

 its bones are sufficiently separated, to allow room for the de- 

 velopment of the eggs. The lower limbs are formed of the 

 femur, of the tibia, and of the fibula, which are joined to it by 

 an articulation with a spring, which keeps it extended without 

 any muscular effort. There are muscles, also, that go from 

 the pelvis to the toes, passing over the knee and heel, so that 

 the toes are flexed by the weight of the body. The tarsus and 

 metatarsus, are formed by one single bone, terminated below 

 by three pulleys. There is most generally one great, and four 

 other toes, diverging from each other, the number of whose 

 joints increase from the great one, which has but two, to the 

 external one, which has five. The neck is lengthened, is com- 

 posed of many vertebrae, and is very moveable; the coccygis 

 is extremely short and furnished with quills like the wings. 

 The brain, whose characters are similar to those of the other 

 oviparous vertebrata, is remarkable by its size, as compared to 

 that of the body, which is considerable; but this does not de- 

 pend upon its hemispheres, which are small. The skin of 

 birds, is, commonly, covered with feathers composed of a hol- 

 low stem and barbs; the skin is scaly on the superior surface 

 of the toes, and callous beneath; the sense of touch, must con- 

 sequently be weak. The eye is furnished with three moveable 

 lids; the cornea is very convex, the crystalline lens is flat, and 

 the vitreous body small. The crystalline has a membrane which 

 appears intended to move it. The anterior part of the eye is 

 encircled with bony pieces. Birds see with great clearness, 



