xvi COMPARATIVE ELECTRO-PHYSIOLOGY 



I'ACiE 



variation of natural current Effect on natural current of variation of 

 temperature Effect of sudden variation Variation of natural current 

 by chemical agents, referred to physiological reaction Agents which 

 render tissue excitable, induce the positive, and those which cause excita- 

 tion, the negative variation Action of hydrochloric acid Action of 

 Na 2 CO 3 Effect modified by strength of dose Effect of CO 2 and of 

 alcohol vapour Natural current and its variations Extreme unrelia- 

 bility of negative variation so-called as a test of excitatory reaction 

 Reversal of natural current by excessive cold or by stimulation Re- 

 versal of normal response under sub-tonicity or fatigue . . . .116 



CHAPTER XI 



VARIATIONS OF EXCITABILITY UNDER CHEMICAL REAGENTS 



Induced variation of excitability studied by two methods: (i) direct 

 (2) transmitted stimulation Effect of chloroform Effect of chloral 

 Effect of formalin Advantage of the Method of Block over that of 

 negative variation Effect of KHO Response unaffected by variation 

 of resistance Stimulating action of solution of sugar Of sodium carbon- 

 ateEffect of doses Effect of hydrochloric acid Diphasic response on 

 application of potash Conversion of normal negative into abnormal 

 positive response by abolition of true excitability . . . , .129 



CHAPTER XII 



VARIATIONS OF EXCITABILITY DETERMINED BY METHOD OF 

 INTERFERENCE 



Arrangement for interference of excitatory waves Effect of increasing 

 difference of phase Interference effects causing change from positive to 

 negative, through intermediate diphasic Diametric balance Effect of 

 unilateral application of KHO Effect of unilateral cooling . . .141 



CHAPTER XIII 



CURRENT OF INJURY AND NEGATIVE VARIATION 



Different theories of current of injury Pre-existence theory of l)u liois- 

 Reymond Electrical distribution in a muscle-cylinder Electro-mole- 

 cular theory of Bernstein Hermann's Alteration Theory Experiments 

 demonstrating that so-called current of injury is a persistent after-effect 

 of over-stimulation Residual galvanometric negativity of strongly excited 

 tissue Distribution of electrical potential in vegetable tissue with one 

 end sectioned Electrical distribution in plant-cylinder similar to that in 

 muscle-cylinder True significance of response by negative variation- 

 Apparent abnormalities in so-called current of injury ' Positive ' 

 current of injury 149 



