2. Why does the body not need a light-producing apparatus, corresponding to the larynx in the production of sound? 3. How is the light from a candle made to form an image? 4. What different things must happen in order that one may see an object? 5. Make a sectional drawing of the eyeball, locating and naming all the parts. 6. Of what parts are the outer, middle, and inner coats of the eyeball made up? 7. What portions of the eyeball reflect light? What absorb light? What transmit light? What refract light? 8. Show how the iris, the crystalline lens, the retina, the ciliary muscle, and the cornea aid in seeing. 9. Trace a wave of light from a visible object to the retina. 10. Why does not the inverted image on the retina cause us to see objects upside down? 11. What change occurs in the shape of the crystalline lens when we look from distant to near objects? From near to distant objects? Why are these changes necessary? How are they brought about? 12. How does the method of adjustment, or accommodation, of the eyeball differ from that of a telescope or a photographer’s camera? 13. With two eyes how are we kept from seeing double? 14. What different purposes are served by the tears. Trace them from the lachrymal glands to the nostrils. 15. Show how the proper lenses remedy short- and long-sightedness. 16. Describe the conjunctiva and give its functions. Why should it be so sensitive? 17. How may eye strain cause disease in parts of the body remote from the eyes? 18. How does "image stimulation" differ from light stimulation in general? PRACTICAL WORK *To illustrate Simple Properties of Light.*—1. Heat an iron or platinum wire in a clear gas flame. Observe that when a high temperature is reached it gives out light or becomes luminous. 2. Cover one hand with a white and the other with a black piece of cloth, and hold both for a short time in the direct rays of the sun. Note and account for the difference in temperature which is felt. 3. Stand a book or a block of wood by the side of an empty pan in the sunlight, so that the end of the shadow falls on the bottom of the pan. Mark the place where the shadow terminates and fill the pan with water. Account for the shadow’s becoming shorter. 4. Place a coin in the center of an empty pan and let the members of the class stand where the coin is barely out of sight over the edges of the pan. Fill the pan with water and account for the coin’s coming into view. Show by a drawing how light, in passing from the water into the air, is so bent as to enter the eye. 5. With a convex lens, in a darkened room, focus the light from a candle flame so that it falls on a white screen and forms an image of the candle. Observe that the image is inverted. In a well-lighted room focus the light from a window upon a white screen. Show that, as the distance from the window to the screen is changed, the position of the lens must also be changed. (Accommodation.)