52 



REPTILES AND BATRACHIANS. 



"it hops." The French word sauterelle is the more correct term 

 for the latter ; by the combined action of the legs both it and the 



frog perform a perfect leap, 

 and no less nimble than 

 the "grasshopper" is the 

 frog. The extra joint in 

 the leg might be called a 

 heel, but is truly formed 

 by the very elongated 

 ankle bones. These bones, 

 flat on the ground, must 

 assist the leaping, but are 

 also used as an elbow. 

 We speak of persons 

 "elbowing their way" 

 through a crowd. The 

 "elbows" its way 

 this posterior joint, 



frog 

 with 



not through a crowd 

 certainly, but to back itself 

 into some safe retreat, as 

 I shall presently explain. 

 The foot of a frog is, as 

 Mivart shows us, " a very 

 marvel of complexity," 

 with an elaborate system 

 of muscles. The toes are 

 extremely long, and this 

 muscular system. furnishes 

 to the little animal its 

 power of locomotion, both 

 on land and in water. A 

 frog has no ribs, though 

 those bony processes from 

 the eight joints of the 

 spine resemble ribs, and 

 are as long as the true ribs 

 of newts. While the frog 

 has a shorter spine than 



any other vertebrate animal it has a breast-bone, sternum, and 



is the first example in the rising scale in which the sternum 



appears. 



We may now clothe our frog with muscles and skin, and observe 



its habits. As to colour, olive may be said to predominate ; but 



Fig. 22. — Skeleton of a frog. 



