CONTENTS ix 



The Sounds of the Heart . .291 



The Heart-beat as Muscular Action . . . . . 293 



The Influence of Nerves on the Heart . . 293 



The Sympathetic Influence . . 294 



The Influence of the Vagus ..... 295 



The Afferent Nerve of the Heart . 297 



Cardiac Centers 297 



The Functions of the Blood- and Lymph-vessels . . 297 



The Physiology of the Arteries . . 298 



The Pulse 298 



Vasomotion ....... 300 



The Functions of the Blood-capillaries .... 304 



The Lymphatic Portion of the Circulation ..... . 305 



The Causes of the Lymph-flow . . 306 



The Functions of the Veins . 310 



CHAPTER IX. 

 THE SKIN. 



The Functions of the Skin .312 



Protection ......... 313 



Sensation 316 



Thermotaxis ........ 317 



The Sweat ... 317 



The Secretion of Sebum . .... 321 



Respiration .......... 323 



Absorption . ... . 323 



Coloration . . . .324 



The Hairs and the Nails . 326 



CHAPTER X. 



THE SENSES. 



Kinesthesia ....... . . 329 



Afferent Endings in Muscle ..... . 332 



Afferent Endings in Tendons . . . 332 



Afferent Endings in the Joints, etc. .... 332 



Kinesthetic Function ....... . 332 



Vision . . . . * . . . ... 335 



The Receptive Apparatus of the Eye . . . 337 



The Various Adjustments of the Eyes .... . 339 



Head-movements ... 339 



Eye-movements . . . . . . 340 



Accommodation ...... .341 



Visual Theories . 343 



The Perception of Light . 344 



Theories of Color-vision ..... . 344 



Color-blindness ....... . 345 



Space-perception ...... . 345 



