108 THE FROG, OR THE TOAD. 



keep afloat ? How much of the body is submerged ? Observe the 

 relative position of the limbs and the toes. 



Notice a frog or a toad sitting at rest. Describe the relative position 

 of the parts of each limb. Do you see the hump ? We will learn the 

 cause of that later. Touch the eyeballs and note results. 



Describe the movements of certain parts in the process of breathing. 

 Near the posterior end of the backbone, on each side, slight pulsations 

 of the lymph hearts may sometimes be seen. 



Keep toads in a roomy observation box for some days and feed them 

 all sorts of insects. Record their preferences for certain kinds, if any 

 are shown. Gauge their capacity for food by feeding them all the 

 insects they will eat. Keep records of individual gastronomic feats. 

 Try them on certain noxious insects of the garden. Understand their 

 method of snapping up the food. 



Exercise i. Make a drawing of the live toad in a sitting position, natural 

 size or nearly so. 



Technical Note. Select two or three frogs whose abdomens are but little 

 distended, place them in a jar or pail fitted with a tight lid, and 

 introduce a wad of cotton saturated with chloroform. In about five 

 minutes remove the lifeless animals and rinse them off. The rinsing 

 is especially necessary if you are using toads instead of frogs, as the 

 former excrete from pores in the skin an acid substance having a 

 disagreeable odor. In life this excretion was a source of protection to 

 them. 



EXTERNAL FEATURES. Look the animal over carefully, noting the 

 following structural points: 



a) Two regions of the body, head and trunk. Determine the line 



of division between the two by moving the head up and down. 

 Neither neck nor tail are in evidence. How would you charac- 

 terize the shape of the body as a whole ? 



b) Compare the fore limbs with the hind limbs in size. Why the 



great difference ? You will note that the divisions of the limbs 



