CONTENTS. Vll 



Page 



Chapter IV. — Smell 396 



Chapter V. — Hearing 414 



§ 1 , Acoustic Principles 414 



2. Physiology of Hearing in Man 420 



3. Comparative Physiology of Hearing 434 



Chapter VI,"— Vision 444 



§ 1 . Object of the Sense of Vision 444 



2. Modes of accomplishing the objects of Vision . 449 



3. Structure of the Eye 460 



4. Physiology of Perfect Vision 469 



5. Comparative Physiology of Vision 477 



Chapter VII. — Perception 508 



Chapter VIII. — Comparative Physiology of thl 



Nervous System. 537 



§1. Nervous System of Invertebrated Animals. .. . 537 



2. Nervous System of Vertebrated Animals .... 553 



3. Functions of the Brain 561 



4. Comparative Physiology of Perception 566 



PART IV.— THE REPRODUCTIVE FUNCTIONS. 



Chapter I. — Reproduction 581 



Chapter II. — Organic Developement 599 



Chapter III. — Decline of the System 619 



Chapter IV. — Unity of Design 625 



Index 643 



