CHORDATA. 317 



used, and the behavior of the corpuscles studied as they pass 

 through the capillaries. Similar studies may be made on the 

 gills of very young tadpoles. 



B. External Anatomy. What is its symmetry? Compare 

 carefully the structure and form of the dorsal with that of 

 ventral surface; similarly those of the anterior and posterior 

 ends. Compare several individuals as to shape, color mark- 

 ings, size, etc. 



General form. 



Head, trunk, limbs. Is there any neck? 



Anterior appendages: arm, forearm, hand (including 

 digits). Compare with your own hand, and deter- 

 mine which is the first digit, or the thumb side of 

 the hand. 



Posterior appendages : thigh, shank, ankle, foot. How 

 many digits? Which is the first? How many joints 

 in each? What other peculiarities are noteworthy? 

 Special head structure. 



Mouth ; position, dimensions, degree of extensibility ; 



tongue; teeth, where located? 



Sense organs : position of eyes, ears, nose. Do the nasal 

 openings communicate with the mouth? Pierce the 

 tympanic membrane and discover with what the open- 

 ing communicates. 

 Cloacal opening. 



C. Internal Anatomy. Make a slit in the skin of the ven- 

 tral surface from a point just in front of the cloaca forward 

 to the throat, a little to one side of the middle line. Make 

 incisions perpendicular to this and turn the flaps back to show 

 the muscles beneath. Is the skin as closely attached to the 

 muscles as in the fish? Do you find myotomes as in the fish? 

 Draw in outline some of the more important muscles of the 

 chest and abdomen. Cut the muscular wall in the same way, 

 passing to one side of the breast bone. Turn back the flaps 

 and sketch and identify the organs in their position in the 

 ODelom. 



