OB OSSEOUS SYSTEM. *J 5 



spinal chord are most dilated before and behind in that 

 direction. These very short, strong, transverse processes 

 have each a large, convex, prominent, articular surface, ex- 

 tending downwards, inwards, and a little forwards, which is 

 received into the articular concavity of the head of the 

 rib. From the four articular processes of the vertebrae 

 extending to a great distance laterally in a straight and 

 horizontal direction, they give great extent and safety to 

 those lateral motions which are chiefly required in the trunk 

 of serpents. The bodies of the dorsal vertebras are cari- 

 nated below, and have a narrow contracted neck at the base 

 of the posterior, hemispherical, articular tubercle. The 

 laminae are here very strong, and evasated before and behind, 

 to enlarge the two ends of each vertebral foramen, that 

 the spinal chord may not be pressed upon during the mo- 

 tions of the vertebrae. The spmous processes are short, 

 strong, and broad, from before backwards, so as to afford a 

 strong attachment to the muscles, without interfering with 

 the motions of the vertebrae. 



In the skulls of reptiles, as in fishes and amphibia, we 

 still find the cranial vertebrae disposed in the same straight 

 line as those of the rest of the column, and most of the 

 elements of the cranial bones still remain separate through 

 life. The serpents and lizards present the most detached 

 condition of all these cranial bones met with in the class 

 of reptiles ; the crocodilian animals, and the chelonia have 

 them the most firmly united by sutures. This loose state 

 of the bones of the head is the more necessary in serpents, 

 which, from the want of arms and legs to hold down their 

 prey, and assist in its subdivision, are compelled to swallow 

 it entire. The annexed figure of the skull of the python 

 (Fig. 39.) shows the most common disposition and form of 

 the bones of the head of serpents. The basilar portion (a,) 

 of the occipital bone remains distinctly isolated from the 

 two lateral condyloid pieces (*,) and these three elements 

 form the large, transversely elongated, occipital condyle, the 

 basilar element forming the greater portion of it. The 

 superior or median occipital (,) is here small and detached^ 

 as in the saurian reptiles. The parietal bones (c, c,) are 

 long, and anchylosed together along the median line, to 

 afford a solid unyielding covering to the lengthened brain 



