xii CONTENTS 



PAGE 



lens Far- and near-sight Adjustments to intensity of 

 light Purpose and structure of retina Optic nerve 

 Sensation of sight Acuteness of vision Defects of 

 vision Eye strain Astigmatism Perception of dis- 

 tance Binocular vision Double vision 246 



CHAPTER XXIII 



THE CARE OF THE SENSE ORGANS 



Means of protection Care of the ear Method of cleaning 

 Removal of objects Earache Effect of noise Eyes 

 Removal of objects Effect of strong light Weak light 

 Proper use 272 



CHAPTER XXIV 



THE VOICE AND SPEECH 



Sound as a means of communication Larynx and vocal 

 cords Volume Pitch Timbre Effect of air cavities 

 upon the voice Vowels Consonants Whispering .... 276 



CHAPTER XXV 



HEALTH AND DISEASE 



Health Conditions of health Disease Microbes, a cause 

 of disease Bacteria, protozoa and molds Exposure to 

 disease Generation of toxins Antibodies Four stages 

 of disease Individual differences in resistance Im- 

 munity Tuberculosis Artificial development of anti- 

 bodies In consumption Infection Entrances and exits 

 for microbes Prevention of disease by personal care 

 Disinfection Prevention of disease by municipal hy- 

 giene 281 



CHAPTER XXVI 



STIMULANTS AND NARCOTICS 



Definition Proper use of narcotics Improper use Legal 

 restrictions Tobacco a narcotic Method of use Pres- 

 ence of carbon monoxide (CO) Extent of use Indi- 

 vidual susceptibility Stimulants: tea and coffee 

 Formation of habit Alcohol Production of alcohol 

 Various beverages Effects of alcohol Alcohol, a nar- 

 cotic poison Chronic effects upon structure Effect 

 upon heart Upon blood-vessels Upon nervous system 



