MUSCULAR SYSTEM IN THE VERTEBRATA. 43 



of the anurous species, it presents characters very remote from them, 

 arising from their great extent of respiration, and their inhabiting a 

 rarer medium. The oblique caudal muscles in the tadpole of the 

 tailless tribe, become absorbed with the vertebras to which they are 

 attached, as the animal assumes its permanent form ; but its change 

 of habits is still provided for by the great development of the 

 muscles of the posterior extremity, in fact they closely resemble 

 those of the human leg; and hence the act of swimming in man 

 is an accurate imitation of that of the frog. In this animal, the 

 extensors are much stronger than the flexors of the leg, and those 

 of the arm are but feebly developed. 



REPTILIA. 



The rarity of the medium through which the air-breathing rep- 

 tiles move, at once declares an increased development of muscular 

 energy in this class. In the progressive motion of serpents, their 

 vertebral column forms several S-shaped lateral curves; is shortened, 

 and again stretched forwards, whilst the posterior part of the body 

 is fixed: this rapidly performed constitutes a leap or dart. The ribs 

 being free at their distal extremities, admit of extensive motion, and 

 are furnished with large intercostal muscles of various lengths, 

 some passing from rib to rib, and others over one or more to have 

 distant insertions. These muscles have small shining tendinous 

 bands, by which a great number can be attached to a small space, 

 and thus admit of great variety in the movements of the ribs, 

 which are not only subservient to respiration, but to progressive 

 motion in these animals. The muscles of the head are strong, and 

 in the rattle-snake and others, a portion of the temporal extends 

 forwards like a buccinator, to embrace the poison gland and force 

 its secretion into the perforated fang. 



The saurian reptiles possess members sometimes organised for 

 progression on the surface, sometimes for climbing, sometimes for 

 swimming, and occasionally for flying ; hence their muscles are 

 more numerous and complicated than in serpents. A rudiment of 

 diaphragm may be perceived in the dragons and geckos ; and in the 

 prehensile tongue of the chameleon there resides a beautiful muscu- 

 lar apparatus ordained to govern its stealthy movements in obtaining 

 his food, and as Sir C. Bell aptly describes it, he lies more still than 

 the dead leaf, his skin is like the bark of the tree, and takes the hue 

 of surrounding objects. Whilst other animals have excitement 

 conforming to their rapid motions, the shriveled face of the cha- 

 meleon hardly indicates life ; the eyelids are scarcely parted ; he 

 protrudes his tongue with a motion so imperceptible towards the 

 insect, that it is touched and caught more certainly than by the 

 most lively action. In the chelonia, the muscles of the extremities 

 together with those of the shoulders and pelvis are well marked, 

 whilst those of the jaws, lips, and chest are almost wholly absent. 



