100 



HITCHCOCK'S ANATOMY 



cut shows, the skeleton of the Tortoise is a very simple one, 

 and the skeleton of the Frog, as shown in Fig. Ill, is 

 equally simple. 



215. Humerus. — The Humerus of the Tortoise is short 

 and very much curved. This is made so in order that the 

 animal may thrust its extremities out of the shell and reach 

 the ground, which could not be done if the humerus were 

 straight as it is in most of the other vertebrate animals. 



216. Femur. — The Femur is curved in the same animals 

 for the same reason. 



217. Phalanges.— Frogs generally have four fingers, with 

 from two to four phalanges in each finger. Tortoises and 

 Lizards generally have five fingers, and from two to five 

 phalanges in each finger. 



Fig. 111. 



Skeleton of the Frog. 



OSTEOLOGY OF FISHES. 



218. Bony and Cartilaginous Fishes— The skeletons of 

 Fishes are of two kinds, those made up of bony, and those of 

 cartilaginous matter. (Fig. 112.) The microscopic structure 

 of the scale of a Pike is seen in Fig. 113. Of the former kind 



215. Why is the Humerus of the Tortoise curved? 217. How many fingers have 

 Frogs, Lizards, and Tortoises ? 218. What are the two kinds of skeletons in Fishes I 

 Give examples of each. 



