FEOG 261 



cells. Treat the preparation with acetic acid. 

 Treat another preparation with iodine ; the deep 

 red color assumed by the contents of certain cells 

 indicates the presence of glycogen. 

 i. The testis. 



In a drop of water finely divide a portion of 

 the testis of a recently killed frog, and look for 

 actively moving spermatozoa. Apply magenta. 

 To another preparation apply dilute iodine. 



PHYSIOLOGY 



A. Locomotion. 



Does the frog ever walk? Eun? Can it walk 

 backward? Leap backward? Walk sidewise? 

 Swim backward ? In swimming, what use is made 

 of the fore limbs ? Can it float ? 



B. Nutrition. 



a. Feeding. — Place a frog in a low glass jar, beaker, 

 or tumbler, along with a living fly. "Watch the 

 frog, to see how it catches the fly, noticing par- 

 ticularly the action of the tongue. If it be other- 

 wise impossible to get the fly witliin reach of the 

 frog, kill the former by pinching its head, run a 

 fine thread through its body by means of a needle, 

 then lower the fly, dangling at the end of the 

 thread, into the jar. If flies cannot be obtained, 

 use a small piece of fresh meat. Can you give 

 any reasons for the structural arrangement of the 

 frog's tongue ? 



I. Breathing. — Watch the nostrils of a frog. Can you 

 detect any motions ? Watch the throat and the 

 sides of the abdomen. Do they move ? If so, do 

 they move at the same time? While holding 

 your hands on your sides, draw in a breath. Do 



