150 COMPAJRISOIy'S OF STRUCTUKE IN ANDIALS. 



vertebra, anterior to the spinal canal; so that, 

 in fact, the head turns on a pivot, the free- 

 dom of which is restricted bj ligaments. In 

 mammaKa, there are two articulating convex 

 surfaces on the occiput, received into corre- 

 sponding depressions in the first vertebra, 

 {atlas,) and this revolves on the second vertebra, 

 or rather upon a process of the second, termed 

 the odontoid, or toothlike process; but the 

 power of turning the head, except in very 

 long-necked quadrupeds, and the sloth, is com- 

 paratively limited. As the bird bends its neck 

 at surprisingly abrupt angles, it wiU naturaUy 

 be asked how it happens that at these angles 

 the spinal cord escapes compression, which 

 would either destroy life, or paralyze the whole 

 frame : if we run a thread- or string through 

 several short pieces of a tobacco-pipe, and make 

 a sudden angle between any two, we shaU find 

 the string to be pressed upon and strained at 

 that angle, and so it would appear must be the 

 spinal cord of the bird under similar circum- 

 stances ; and, indeed, so it would be, but for a 

 special provision, a provision which expressly 

 proves the care and forethought (so to speak) 

 of the great' Creator in his works. Nothing 

 can be more simple than tho plan adopted— 



