THE SENSES 143 



foods that have a flavor (see text) : vanilla, apple, lemon, beef, 

 peaches, grapes, coffee, onion, potato, cinnamon. 



Experiment 8. A Smelling Contest. Place the following and other 

 things having taste in vials around which paper has been pasted to con- 

 ceal their contents : pepper sauce, vinegar, kerosene, flavoring extracts 

 (diluted), several perfumes, iodine, bits of banana, lemon, apple, etc. 

 Number the vials and have pupils test and write results in a list. 

 Correct the lists and announce pupil having keenest sense of smell. 



Experiment 9. A tasting contest may be arranged in a similar 

 way. Smelling and tasting tests should be made quickly as these 

 senses are soon dulled by repeating a sensation. 



Experiment 10. Advantage of Two Eyes over One. Try to touch 

 forefinger to something held by another at arm's length from you, 

 bringing the finger in from the side: (i) with one eye closed; 

 (2) with both eyes open. Result ? Conclusion ? We tell the dis- 

 tance of an object by the amount of convergence of the eyeballs needed 

 to look at it. 



Experiment \ i . Duration of Impression. Whirl a stick with a 

 glowing coal on one end (see Fig. 123). 



Experiment 12. Color Blindness. Provide a number of yarns of 

 different tints, and the same tints. Test color blindness by having each 

 pupil match tints and assort the yarns. 



Experiment 13. Fatigue of Optic Nerve. Gaze long and steadily at 

 a moderately bright object, then close the eyes. Result ? Conclusion ? 



Experiment 14. Dissection of Eye. The eye of an ox is an in- 

 teresting subject for dissection. The lens is like a clear crystal. Make 

 out all parts named in the text (see Fig. 122). 



Experiment 15. Image formed by a Convex Lens. For a few 

 cents obtain from a jeweler a convex lens, or use a strong pair of 

 spectacles worn by an old person. Hold the lens a few feet from a 

 window (darken any other windows near). A little beyond the lens 

 hold a white card or book open at a blank page to catch the image. 

 Have some one walk before the window. 



Experiment 16. Work of Iris. Notice the size of the pupils. 

 Cover one eye with the hand for a few minutes. Uncover and look in 

 a mirror. Gaze at bright window and look again in the mirror. Con- 

 clusion ? Do the two pupils still keep the same size when one eye is 

 shaded ? 



Experiment 17. Accommodation. By holding your finger or a 

 pencil in line with writing on the blackboard, you find that you cannot 

 see both finger and blackboard distinctly at the same time first one 

 and then the other is distinct. Explain (see text). 



