CHORD ATA 3 21 



ends. Compare several individuals as to shape, color markings, 

 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 in a dead frog and discover with 

 what the opening communicates. 

 Cloacal opening. 



C. Internal Anatomy. — Make a slit in the skin of the ventral 

 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 coelom. 



I. Digestive Organs. — Pressing the liver aside, identify the 

 following parts of the digestive tube: esophagus, stomach, 

 small intestine, large intestine. Are there any sharp boundaries 

 between these parts ? 



Compare the lengths of the different portions. Find the 

 mesentery, and show its relation to the intestines. What is 

 the relation of the liver to the digestive tube? Find the gall- 

 bladder: does it have any duct leading to the tube? What is 



