272 



REPTILIA. 



and the third of four, and the fourth of three, 

 the same as in the hands. 



It was an observation made as far back as 

 the time of Aristotle, that the division of the 

 anterior and of the posterior feet of the 

 chameleon is effected in an inverse manner, 

 the latter having the thumb and first finger 

 only conjoined and turned inwards, but the 

 other three turned outwards, whilst, as has 

 been stated above, the anterior limb has 

 three turned inwards and only two turned 

 outwards, a beautiful provision for ensuring 

 the steadiness of the creature's grasp. 



The dragon (Draco) possesses fourteen pair 



Fig. 190. 





of ribs, viz., six genuine, short, and curved 

 ribs, which reach the breast-bone, and eight 

 pairs of false straight ribs, which are seated in 

 the wing membrane, and support the same. 

 The posterior extremity of the ribs has a 

 little head, in which there is a small socket 

 of articulation, which is merely inserted upon 

 the spherical articulating surface on the point 

 of the transverse processes, and not at all into 

 the bodies of the vertebrae. Owing to this re- 

 markable mode of insertion, a very free joint is 

 produced, enabling the ribs (especially those 

 that are implanted in the wing membrane) to 

 move forwards and backwards, and upwards 

 and downwards, in different directions. Of the 

 genuine ribs, the anterior ones are the short- 

 est, and the posterior ones the longest ; they 

 all terminate in a cartilaginous point, which 

 attaches itself to the breast-bone. Of the 

 eight pairs of false ribs, the five first pairs are 

 very long, and the three following pairs are 

 short, especially the two last pairs, which can- 

 not be seen at all in the wing membrane. 

 The false ribs become gradually thinner, and 

 terminate at the edge of the wing membrane, 

 in very fine cartilaginous points. In the 

 whole animal kingdom, it is the dragon alone 

 that exhibits this isolated and most remarkable 

 structure. The wing membrane of the dragon 

 distinguishes itself from the wing membrane 

 of the flying squirrel by the circumstance of 

 being supported by the ribs, which is not the 

 case in the latter animals : the same cir- 



cumstance likewise distinguishes 



their wing 



Skeleton of Draco volans. 



membrane from that of the bat, in which the 

 prolonged anterior extremities, particularly 

 those bones which are analogous to the finger 

 joints, are continued into the wing. 



The ribs, when flying, are moved by se- 

 veral muscles. Strong triangular muscles 

 spring laterally from the bodies of the 

 dorsal vertebrae, and are inserted into the 

 lower edge of the commencing part of the 

 false ribs. These muscles move the ribs, when 

 flying, together with the wing membrane, 

 downwards and slightly backwards. Other 

 broad muscles, which have their source at 

 the upper surface of the vertebras, and which 

 attach themselves to the ribs, move the ribs 

 with the wing membrane. The alternating 

 contractions and expansions of these muscles 

 effect the fluttering or flying of the dragons. 

 Thin muscles are likewise seated between the 

 ribs, analogous to the intercostal muscles. 



Osteology of Ophidians. In the true ser- 

 pents, the vetebral column itself constitutes 

 the principal portion of the skeleton, and the 

 number of pieces of which it consists is some- 

 times prodigious, varying in different species, 

 from about a hundred (Acontias) up to three 

 hundred (Boa) or even four hundred (Py- 

 thon) distinct vertebrae. These have pretty 

 much the same shape throughout the whole 

 length of the spinal column, each presenting 

 the centrum or body, and the spinous, trans- 

 verse, and articulating processes forming the 

 bonds of connexion between them, or the 

 levers by which they are wielded. 



The bodies of contiguous vertebrae are 



