CONTENTS XI 



CHAPTER XII 



THE ARGUMENT FROM DISEASE 



PAGE 



The Lamarckian doctrine is certainly untrue It is equally un- 

 true that hereditary tendencies may be easily changed by the 

 direct action of external forces Professor Cossar Ewart's observ- 

 ations . .... 157 



CHAPTER XIII 



THE ORIGINS OF ZYMOTIC DISEASES 



The microbes of disease are an infinitesimal portion of the 

 total number of bacteria Men acquire microbic diseases as a rule 

 only from other men The conditions necessary for the evolution 

 of a microbic disease The antiquity of microbic diseases Their 

 first origin Their spread Earth-, air-, and water-borne diseases 

 Epidemic and endemic disease Epidemics in the ancient and 

 modern worlds .... . .168 



CHAPTER XIV 



BACTERIA AS EMPIRE BUILDERS 



Air- and water-borne diseases in the Western Hemisphere 

 Tuberculosis The extinction of the natives The colonization of 

 the New World by European nations The causes of success or 

 failure The foundations of empire The cessation of the great 

 migrations 182 



CHAPTER XV 



NARCOTICS 



A mental problem The elimination due to alcohol The 

 reasons why men drink Self-control Will-power Variations 

 amongst drinkers Alcoholic selection Racial differences Alco- 

 holic evolution Is parental intemperance the cause of filial 

 degeneration? Opium The sobriety of South Europeans The 

 comparative drunkenness of North Europeans The excessive 

 drunkenness of some savages The sobriety of others Intemper- 

 ance in the ancient world Climate Potency of beverages 

 Environment The memory of past disasters Civilization 

 Education The parallel between diseases and narcotics . .189 



CHAPTER XVI 



REFLEX ACTION 



Mental symbols The origin and evolution of mind Sense- 

 impressions Feelings Pleasure and pain The will . . . 209 



