BULLFROG AS TYPICAL VERTEBRATE ANIMAL 67 



digit, or thumb, is enlarged, whereas the thumbs of females remain 

 apparently the same size. The digits may have tubercles on them, 

 and their positions in relation to various bones of the hand give rise 

 to specific names for these tubercles. The forelimbs are used not 

 only to help support the body but also as an aid in pushing food 

 into the mouth. 



The hindlimbs are long and have powerful muscles. Bullfrogs 

 ordinarily leap about three feet but can easily cover a distance of 

 five or six feet. The hindlegs are composed of the femur, which 

 joins the trunk; the tibio-fibula; and the ankle, or tarsus. Follow- 

 ing the tarsus is the foot with five digits (toes), which are connected 

 by a web, producing a very efficient swimming organ. The point at 

 which the tarsus joins the tibio-fibula is known as the heel. 



Digestive System and Digestion 



The mouth cavity, or buccal cavity, is large. It narrows toward 

 the esophagus, which is a short gullet leading directly from the 

 mouth to the stomach. The lining of the esophagus has a number 

 of longitudinal folds and is ciliated. The stomach normally lies on 

 the left side of the body. It is curved, with the convex side toward 

 the bullfrog's left. Its anterior or cardiac end is wide, and the 

 pyloric or posterior end is narrowed and constricted where it joins 

 the small intestine. The duodenum, or anterior part of the small 

 intestine, runs forward almost parallel with the stomach. At the 

 point where the intestine turns back posteriorly the duodenum be- 

 comes the ileum, which composes the remainder of the small intestine 

 and is considerably coiled. The large intestine or rectum is sharply 

 marked off from the small intestine and is wide and short. It passes 

 directly into a muscular part, the cloaca, which terminates in the anus 

 or vent. 



The buccal cavity has in its roof near the end of the snout two 

 patches of small conical teeth which are cemented to two bones in 

 the roof of the mouth, known as vomers. These teeth consequently 

 are called vomerine teeth. In addition, the upper jaw has a single 

 series of small conical teeth on its edge known as maxillary teeth. 

 These teeth serve primarily to help hold the crayfish, insect, or 

 other animal captured for food, and they may help at times in 

 crushing it. The tongue is somewhat leaflike in shape and is deeply 

 notched behind, making it bicornate. Its anterior half is attached 



