The Frog: A Representative Vertebrate 51 



it can gulp down air. This strange froglike animal lives near the edge 

 of the pond until the gills and tail are absorbed. Accompanying the 

 more obvious external changes are important internal ones, including 

 the shortening of the intestine. The tadpole needs the much elongated 

 intestine to handle its vegetable diet, while the adult, which is carnivo- 

 rous, needs only a short one. The young frog soon is foraging about 

 the banks for insects. 



As cold weather approaches in the fall, the frogs go into the deeper 

 water of ponds. Here they burrow into the soft mud or crawl under 

 trash. In this manner they pass the winter in a state of hibernation. 



USEFUL TERMS 



In describing a detailed anatomy of any animal, it is necessary to 

 use certain terms for indicating the relationships of the various parts. 

 Some of these terms are listed here : 



Dorsal : Toward the back. 



Ventral : Away from the back. 



Anterior: Toward the head or front. 



Posterior : Away from the head or front. 



Cephalic or cranial : Toward or pertaining to the head. 



Caudal : Toward or pertaining to the tail. 



Medial : Toward the middle of the body. 



Lateral : Toward the right or left side of the body. 



Proximal : Toward the point of attachment of a part to the mam 



body mass. 

 Distal: Away from the point of attachment of a part to the 



main body mass. 



Various cuts or divisions are often made better to see the relation- 

 ships of parts to one another. These cuts or planes of division are 

 named as follows : 



Median or sagittal plane : Plane dividing the body into right and left halves 

 Frontal plane: Plane parallel to dorsal (or ventral) surface and 



at right angle to median plane. 

 Transverse plane: A plane crossing the long axis of the body and at 



right angles to both the median and frontal 



planes. 



EXTERNAL ANATOMY 



The body of Rana pipiens (Fig. 7) is composed of two main re- 

 gions : the head znd trunk. The head is joined directly to the trunk, 

 for no neck is present. There are two pairs of limbs attached to the 

 trunk • the short forelimbs and the long, muscttlar hmdhmhs. Extend- 

 ing caudally from the eye region are two lateral folds or thickenmgs. 



