PHYSIOLOGY OF BATRACHIANS. 347 



in the Reptiles, and that they should present, in this particular, some analogy to the abdominal 

 structure of the Mammalia. But it is in the disposition cf the muscles of the thigh and leg in. the 

 Batrachia that the greatest singularity is manifested. These, whether taken conjointly or singly, 

 present the greatest analogy with the muscular arrangement of the same parts in man. There is 

 a rounded, elongated, conical thigh, the knee extending itself in the same direction with the thigh 

 bone, and a well-fashioned calf to the leg. 



The locomotion of the Batrachiaiis on the land consists in walking, running, and leaping, the 

 last being the most prevalent motion. The greater part of them are excellent swimmers ; and 

 when they betake themselves to this exercise the body is extended horizontally, and the animal is 

 propelled by the mechanism of the lower extremities alone. It is impossible to watch the horizontal 

 motions of a Frog in the water, as it is impelled by these muscles and its webbed feet, without 

 being struck with the great resemblance, in this position, of its frame to human conformation, and the 

 almost perfect identity of the movements of its lower extremities with those of a man making the 

 same efforts in the same situation. By the aid of these well-developed lower limbs, and the prodi- 

 gious power of their muscular and bony levers, some Frogs can raise themselves in the air to twenty 

 times their own height, and traverse, at a single bound, a space more than fifty times the length of 

 their own bodies. 



The tongue performs a leading part in the capture and deglutition of the prey. It is 

 very soft and fleshy, and is not supported at its base by an os hyoides, as in. the other Vertebrata, 

 but it is fixed in the concavity which is formed by the approach of the two branches of the 

 lower jaw towards the chin. In a state of repose, and when the 

 mouth is shut, this tongue, which has its root, so to speak, in front, 

 has its free extremity or tip in the back part of the mouth, and 

 before the aperture of the air-passages ; but when the animal puts 

 it out, the lower surface comes upwards and the tip reaches far be- 

 yond the mouth. The tongue is armed with a tenacious, viscous 

 secretion, and when it touches the prey this adheres so firmly to it, 

 that it is carried back with the tongue into the mouth. All this is 

 done with a rapidity which the eye can hardly follow. The noises, 

 produced by the expulsion of air, vary from the well-known 

 croaking of the Common Frog to the bellowing of the Bull Frog, HE ^ E 

 and the shrill trebles of the males of the species of the Tree Frog. FREE BEHIND. 

 They, and the flute-like and metallic sounds occasionally given 



out, and the sort of seemingly ventriloquial grumbling which some species of Toads exert, are 

 vocal sounds emitted above the larynx, from the mouth, or from some of the membranous sacs. 



The croakings, produced by the throat bags, seem intended to make the one sex sensible of the 

 presence of the other. Thus the Green Frog has two cheek-pouches, which are inflated by the 

 animal in the breeding season by means of two apertures close to the end of the great air-tube of 

 the throat ; and the folds of the larynx, called chordae vocales, are very large and distinct in many 

 species. The glottis bears, apparently, considerable analogy to the upper larynx in birds. 



The naked skin of the Frogs, and, indeed, of the Batrachians generally, has the power of acting 

 in such a way as to fulfil in a great degree the functions of the lungs, and aerated water may be 

 made subservient to this cutaneous respiration. This has been proved by experiments made on Frogs 

 which have been kept in vessels, and under water charged with air, renewed from time to time, and on 

 Toads which have been kept alive for months in nets sunk under running water, at a low temperature, 

 without any direct access to atmospheric air. 



The spawn seen in water in the spring time is a mass of semi-transparent, gelatinous, round 

 bodies, with little dark - coloured specks inside each. From these are developed the larvae, or 

 Tadpoles. 



Commencing like aquatic animals, the larva? of the Frog, and other Tadpoles, exist very much after 

 the fashion of fishes, moving and breathing like them, and resembling them in shape, on account of 

 the long flat tail. As time elapses, under the influence of warmth and food, the growth does not take 

 place in a manner which will simply enlarge the animal, but it produces alterations in the outside form, 



