Hydro-dynamic _versus_ physiological theory of conduction of excitation--Arrest of conductivity by physiological blocks--Convection and conduction of excitation--Effect of temperature on velocity--Effect of season--Effect of age--Effect of dessication of conducting tissue--Influence of tonic condition on conduction--Effect of intensity of stimulus on velocity of transmission--Effect of stimulus on sub-tonic tissues and tissues in optimum condition--Canalisation of conducting path by stimulus--Effect of injury on conductivity 97 VII.--ELECTRIC CONTROL OF EXCITATORY IMPULSE. Method of conductivity-balance--Control of transmitted excitation in _Averrhoa bilimbi_ by electric current--‘Uphill’ transmission--Transmission ‘downhill’--Electric control of nervous impulse in animal--Directive action of current on conduction of excitation--Effects of direction of current on velocity of transmission in _Mimosa_--Determination of variation of conductivity by method of Minimal Stimulus and Response--Influence of direction of current on conduction of excitation in animal nerve--Variation of velocity of transmission--After-effects on Heterodromous and Homodromous currents--Laws of variation of nervous conduction under electric current 107 VIII.--EFFECT OF INDIRECT STIMULUS ON PULVINATED ORGANS. Conduction of excitation--Dual character of the transmitted impulse--Effect of distance of application of stimulus--Periods of transmission of positive and negative impulses--Effects of Direct and Indirect stimulus 135 IX.--MODIFYING INFLUENCE OF TONIC CONDITION ON RESPONSE. Theory of assimilation and dissimilation--Unmasking of positive effect--Modification of response under artificial depression of tonic condition--Positive response in sub-tonic specimen 141 PART II. GROWTH AND ITS RESPONSIVE VARIATIONS. X.--THE HIGH MAGNIFICATION CRESCOGRAPH FOR RESEARCHES ON GROWTH. Method of high magnification--Automatic record of the rate of growth--Determination of the absolute rate of growth--Stationary method of record--Moving plate method--Precaution against physical disturbance--Determination of latent period and time-relations of response--Advantages of the Crescograph--Magnetic amplification--The Demonstration Crescograph 151 XI.--EFFECT OF TEMPERATURE ON GROWTH. Method of discontinuous observation--Method of continuous observation--Determination of the cardinal points of growth--The Thermocrescent curve--Relation between temperature and growth 173 XXII.--EFFECT OF CHEMICAL AGENTS ON GROWTH. Effect of stimulants--Effect of anæsthetics--Action of different gases--Action of poisons 183