c CONTENTS. 



CHAP. PAGE 



XIII. Activity of Natural Selection at the Different Periods of Life 

 Compared— Its Influence on the Hereditary Transmission of 

 Disease at these Periods — Natural Selection Inoperative after 

 the Procreative Period— Non-Transmission of Evolutionary 

 Gains after this Period— Average Limit of the Procreative 

 Period of Life in the Two Sexes 264 



XIV. Sexual Selection 273 



XV. Action of E upon Structure independently of Selection . -277 



XVI. Criticism of Dr. Mott's Views — Concluding Eemarks on Evolution 280 



PART III. 



I. The Distinction between a " Natural " and an " Artificial En- 

 vironment" 284 



II. What constitutes Normality in Structure and Environment — 

 Definition of Health— Test of Healthy Inter-action — The 

 Actually and Potentially Normal — The Inevitably Abnormal 

 — Justification of the Term Kesistance as Applied to Disease . 290 



III. To what extent Structural Abnormality occurs during the Actual 



Time of Disease 303 



IV. The Advantage of Changed Conditions of Life upon the Vital 



Organism 3x5 



V. Heredity 3^ 



VI. Disease not an Entity — All Disease comes through E — The 



Variability of Disease— A Perfect Classification Impossible . 331 



VII. The Parasitic Origin of Malignant Growths 342 



