THE BONES. 41 



ordinary facility. These joints vary in number 

 according to the necessities of the bird; thus, the 

 Sparrow, which can perch and reach his food close 

 before him, does not require such pliability, or 

 length of neck as the Swan, which floats on the 

 water, and must seek its food at a considerable 

 depth beneath ; accordingly, we find, that, whereas 

 the Sparrow has only nine of these neck-joints, the 

 Swan has twenty-three, the advantages of which 

 must be evident to all who have observed the ease 

 and grace with which this stately bird turns its 

 neck in every direction, or buries its head in sleep 

 beneath the soft down of its wings. 



The Toucan, the bird with the large beak, men- 

 tioned in p. 36, affords a still more curious instance 

 of this power of movement in the neck, nestling its 

 head so completely among the feathers of its back, 

 as entirely to conceal its enormous beak, and nearly 

 assume the appearance of a ball of feathers; in which 

 form, secured from all exposure to cold, it sleeps 

 through the night. The reason of this deviation 

 from the form of skeleton common to other animals 

 is, that this stiffening or consolidation in the parts 

 of the back-bone, is essential, in order to give 

 strength and steadiness to the trunk, in the violent 

 muscular motion required by the act of flying ; for 

 in those birds which do not fly, as the Ostrich and 

 Emu, the joints of the spine or back-bone are more 

 or less moveable throughout. In the joints connected 

 with the tail, (called the caudal vertebrae), certain 

 other pecularities in number and form, present 

 themselves, adapted to the habits of the bird. In 

 the Martin and Swallow, where great freedom in the 



