Contents 



A. Special Sensory Systems 



I. Sound and the Ear 



1. Hearing, 3; 2. Acoustics, 5; 3. Hearing Tests, 10; 4. 

 Anatomy and Action of the Ear, 1 9 



2. Light and the Eye 27 



1. Vision, 27; 2. Optics, 29; 3. Anatomy of the Eye, 34; 

 4. Thresholds and Acuity, 43 



3. Special Uses of Hearing and Vision 52 



/. Introduction, 52 ; 2. Echo-Location in Bats, 53 ; 3. Echo- 

 Location in Other Animals, 58 ; 4. Sense of Direction in Bees and 

 Ants, 59 ; 5. Migration and Homing, 6 1 



B. Nerve and Muscle 



4. The Conduction of Impulses by Nerves 69 



/. The Role of the Nervous System, 69 ; 2. A Brief Glance at Elec- 

 tricity, 72; 3. Anatomy and Histology of Neurons, 74; 4. The 

 Spike Potential, 78 ; 5. Synaptic Conduction, 83 



IX 



7! 16 



