XX CONTENTS. 



CHAPTER XXXII. 



VISION. 



PAGE 



The Tunics of the Eyeball, 557 



Dioptric Media of the Eyeball, 560 



Structure of the Lens, 561 



-The Dioptrics of the Eye, 564 



Accommodation, 570 



Defects of Accommodation, 573 



Defects of Dioptric Apparatus, 574 



-The Iris, 575 



The Ophthalmoscope, 578 



Visual Impressions, 580 



,-The Function of the Retina, 581 



Color Perceptions, 588 



Mental Operations in Vision, 590 



Movements of the Eyeballs, 591 



Binocular Vision, 593 



CHAPTER XXXIII. 



HEARING. 



Sound, 595 



Conduction of Sound Vibrations through the Outer Ear, 599 



Conduction through the Tympanum, 602 



Conduction through the Labyrinth, 604 



Stimulation of the Auditory Nerve, 608 



CHAPTER XXXIV. 



CENTRAL NERVOUS ORGANS. 



Nerve Cells, 611 



^^The Spinal Cord as a Conductor, 614 



The Spinal Cord as a Collection of Nerve Centres, 616 



^^-Special Reflex Centres, 625 



Automatism, 626 



CHAPTER XXXV. 



THE MEDULLA OBLONGATA. 



The Medulla Oblongata as a Conductor, 628 



, The Respiratory Centre, 630 



