258 BIOLOGY FOR BEGINNERS 



COMPARISON OF APPENDAGES OF FROG AND MAN 



Not only are the regions and the bones similar in general structure, 

 but many of the muscles, blood vessels, and nerves of the limbs of 

 man and frog are of similar form and name. The chief difference 

 lies in the fact that man has developed his forelegs into organs for 

 prehension (grasping) and no longer uses them in locomotion. 

 This has resulted in his erect position and has produced many 

 changes in structure to adapt the arm and hand for its altered 

 function. 



The muscles of the fish are in the form of flat plates, extending 

 across the body and moving it as a whole, while in the frog, the 

 muscle tissue is grouped into true " muscles " like our own, at- 

 tached to bones by tendons, and acting on them as levers, thus 

 marking a great advance in structure, and permitting greater 

 variety of motions. 



The Digestive System. The digestive system of any animal 

 begins with the mouth, teeth, and food -getting adaptations which 

 we have already described in this case. 



