420 ADVANCED PHYSIOLOGY 



in changing the angle of convergence of light entering the pupil will assist 

 in making the facts clear. 



Page 353. If possible, arrange with some oculist, or physician with 

 a knowledge of optics and of eye troubles, to bring into class pieces of 

 testing apparatus and charts and to explain the commoner eye defects 

 and method of correction. 



Page 355. Prepared sections of the retina will prove very fascinat- 

 ing if shown in this discussion, not for comment on its details, but in 

 proof that it is a complicated, delicate structure. 



Page 358. Sets of differently colored worsted yarns can be obtained 

 for testing for color-blindness. Require pupils to place together such 

 samples as seem to be of the same color. It is quite probable that some 

 student will show defective color vision. 



CHAPTER XXII 



Page 362. A large model of the entire ear must be on hand in order 

 that the student may get a clear idea of it. A separate preparation of 

 the temporal bone of the human skull, sawed open to show the ear struc- 

 tures, is also desirable. 



Page 366. In no other animal can the semicircular canals be so well 

 shown as in the dog-fish, in which they occupy a large area just back of the 

 eye and can be easily dissected out of the cartilaginous skull. 



Page 370. If stringed instruments are not at hand to show sym- 

 pathetic vibration, two tuning forks, vibrating at the same rate, can be 

 used. One should be struck and its stem placed upon a table top, while 

 the other is held near it. Then smother the one struck and place the 

 stem of the second on the table top. The second will be found to give 

 out sound. 



