THE FROG 93 



The Appendages. Two pairs of legs are present ; each leg is 

 made up of three divisions,— a proximal, a middle, and a distal 

 division. In the foreleg these correspond to the upper arm, the fore- 

 arm, and the wrist and hand respectively ; in the hind leg, to the 

 thigh, the shank, and the ankle and foot. The toes have no claws. 



The forelegs are relatively short and weak and do not aid in 

 locomotion. Four fingers are present, the thumb being rudimen- 

 tary. In the male frog the first finger is thickened. The fingers 

 are not joined by a web. 



The hind legs are long and muscular and are the principal organs 

 of locomotion both on land and in the water. While the animal is 

 at rest the hind legs are folded together back of it in a position 

 ready for springing. In this position the three divisions of the leg 

 become apparent. In the distal division certain ankle bones are 

 much elongated and make this the longest of the three divisions. 

 The five toes are webbed, the medial (innermost) one being the 

 big toe. 



Exercise 1. Draw the animal as it sits or lies before you. 



If the animal is still alive, it may be killed by placing it in a 

 jar of water in which a small quantity of chloroform or ether has 

 been put. 



Exercise 2. Draw a dorsal view of the extended animal, showing the 



features above mentioned ; carefully label all. 

 Exercise 3. Draw a side view of the head. 



The Mouth and Pharynx. Open the mouth as wide as possible ; 

 cut each angle of the jaw a little, if necessary, so that the 

 mouth will remain open. The mouth and pharynx will be seen 

 to be a single space which extends back to the beginning of the 

 oesophagus. With forceps pull the tongue forward ; it is a slimy, 

 bandlike structure attached only at its forward end. The hinder 

 end, which extends back into the pharynx, is bilobed. The lower 

 jaw is without teeth. Just back of the tongue in the floor of the 

 mouth may be felt the hyoid cartilage, which supports the tongue. 



Back of the tongue is the glottis, a median longitudinal slit 

 which opens into the lungs. The glottis is in the middle of an 



