OR OSSEOUS SYSTEM. 



FIG. 46. 



are short, and strong, and give passage to a large foramen 

 (c, c,) on each side, for the vertebral arteries and nerves. 

 The foramen for the spinal chord is dilated at its anterior 

 and posterior extremity, in the direction of the greatest 

 motion of the vertebrae, in order to protect from compres- 

 sion the spinal chord, and the nerves which enter it laterally. 

 The posterior ends of the bodies 

 of the vertebrae (#, ,) are nar- 

 row, convex, arched transversely, 

 and received into a corresponding 

 transverse groove on the anterior 

 part of the body of the next 

 succeeding vertebrae. The trans- 

 verse processes are prolonged so 

 far backwards (g, y,) as almost 

 to form a continuous canal along 

 the sides of the neck, for the 

 protection of the enclosed large 

 vertebral arteries, and the cervi- 

 cal portion of the sympathetic 

 nerves. The forms of the pro- 

 cesses, and of the articulations 

 of the dorsal vertebrae are calcu- 

 lated by every means but by anchylosis to impede motion 

 and to give solidity to that part of the trunk. The spinous 

 processes of these vertebrae are developed forwards and 

 backwards to such an extent that they come almost into 

 contact with each other before and behind. The free ends 

 of the transverse processes extend so much forwards and 

 backwards that they commonly pass over each other in an 

 imbricated manner, and prevent ah 1 lateral motion. And 

 the anterior or sternal surface of the bodies of these verte- 

 brae are often compressed, carinated, and extended down- 

 wards, like inferior spinous processes, which further impede 

 motion. The dorsal vertebrae are often anchylosed toge- 

 ther, like all the lumbar and sacral, to give greater solidity 

 to the trunk, for the movements of flying. The lumbar 

 vertebrae are most free in the ostrich ; in other birds they 

 are anchylosed to each other and to the sacral, as the sacral 

 are to each other and to the iliac bones ; so that the 

 different kinds of vertebrae in this region of the trunk are 



