COY1KNTS. 11 



PAGE 



CHAPTER XIV. 

 PHYSIOLOGICAL CHANGES IN THE CENTRAL SYSTEM... 277 



Nerve-cell a source of energy The nerve impulse 

 Direction of impulse Nerve impulse aroused at the 

 end of branches Strength, form, and rate of impulse 

 Arousal Continuity of stimulation Diffusion Re-en- 

 forcement Diffusion illustrated Knee-kick Back- 

 ground of sensation. 



CHAPTER XV. 

 PHYSIOLOGICAL RHYTHMS 293 



Dependence of the central system Distribution of 

 blood Physiological rhythms The greater cycles 

 Rhythms of the species and the individual Long 

 rhythms Daily rhythms Artificial rhythms Varia- 

 tions in muscular power Minor rhythms Pathological 

 variations in reaction Automaticity. 



CHAPTER XVI. 

 FATIGUE 309 



Expenditure of energy Possible increase of potential 

 energy Results of anatomical disproportion Fatigue 

 affects the material stored at any one time Results of 

 exercise Fatigue a function of the central system 

 Auto-intoxication Drugs Sleep Relation to central 

 system Changes in the circulation Rhythms De- 

 pendence of sleep on stimulation Variations with age 

 Depth of sleep Recuperation Length of the period 

 Hodge's experiments Observations of Mann and 

 Vas Fatigue of the nerve fibres Starvation Other 

 tissues Rdsume. 



CHAPTER XVII. 

 OLD AGE 324 



Changes in the entire body Change in the weight of 

 the encephalon In the lobes of the cerebrum In the 

 thickness of the cortex In the cerebellum Studies on 

 paralysis agitans Observations by Hodge on old age 

 Influence of specialisation Effect of exercise Order 

 of dissolution Decreasing productivity Multiple path- 

 ways Similarities between fatigue and old age. 



