CONTENTS xix 



PAGE 



Root Tubercles 212 



Treatment of Disease in Plants 213 



The Prevention of Disease 213 



The Medical Treatment of Disease 214 



The Surgical Treatment of Disease 214 



Summary 214 



CHAPTER XX 



Diseases due to Harmful Organisms 



Some Kinds of Organisms Produce Poisons 216 



Ways in Which Microorganisms Cause Harm in Animals 216 



Food Poisoning 216 



Prevention of Botulism 217 



Intestinal Putrefaction 217 



The Metabolic Activites of Parasitic Organisms 218 



The Relation of Host and Parasite 218 



Classes of Disease-Producing Organisms 218 



Bacterial Disease 220 



Pus-forming Organisms 222 



Common Colds 223 



Catching Cold 224 



Diseases Due to Higher Fungi 224 



Disease Due to Spirochetes 225 



Diseases Due to the Filterable Viruses 225 



Protozoan Diseases 225 



Disease Due to Metazoa 226 



Virulence 227 



Defenses of Organisms 228 



Prevention of Infection 228 



The Overcoming of Infection 229 



The Action of Phagocytes 230 



The Immunity Reaction 231 



Diphtheria 231 



Artificial Anti-toxin 232 



Immunity : 233 



Smallpox and Vaccination 233 



Defenses of Communities 234 



Contamination of the Air 234 



Direct Infection 235 



CHAPTER XXI 

 Insects and Disease 



Beneficial and Harmful Insects 236 



How Insects Transmit Disease 236 



Flies and Typhoid Fever 237 



Flies and Sleeping Sickness 237 



Flies and Other Diseases 238 



Mosquitoes and Malaria 239 



Malarial Parasites in the Mosquito 239 



