CHAPTER III 

 THE FROG (continued) : THE SKELETON 



IF you have followed the description given in the pre- 

 ceding chapter with a frog before you, testing every 

 statement as you proceeded by reference to the specimen, 

 you will now have a very fair notion of the general build 

 of the animal. The next thing to do is to study its 

 various parts in somewhat greater detail. 



As the bones and cartilages form the framework on 

 which all the other parts are supported, it is convenient 

 to begin with them. You may study them on a pre- 

 pared skeleton, but a far better plan is to make a skele- 

 ton for yourself as directed on p. 53. 



Parts of the Skeleton. The skeleton consists of the 

 following regions : 



1. The skull (Figs. 8 and 9) : a complex mass of 

 mingled bone and cartilage, enclosing the brain and the 

 organs of smell and hearing, and supporting the upper 

 jaw. Connected loosely with the skull, but really form- 

 ing part of it, are the lower jaw and a cartilage in the 

 floor of the mouth known as the hyoid. 



2. The vertebral column or backbone, consisting of nine 

 movably united pieces, the vertebra (Fig. 8 v.i V.Q), 

 and of a long bony rod, the urostyle (usr), representing 

 a number of fused vertebrae belonging to the tail-region 

 of the tadpole. 



35 D 2 



