Sir John Scott Burdon- Sanderson, Bart. xiii 



the part which the modifying current has traversed, and is associated with a 

 remarkable diminution in the high electrical resistance of the tissue, this 

 diminution being strictly confined to the modified region. Finally, the 

 records give demonstrative proof that, when any such modified area is thrown 

 into the active state, either by direct stimulation, or by the arrival of a 

 propagated excitatory wave aroused elsewhere, then the electrical response 

 in this area, whilst it has the same time relations, may be entirely changed 

 as regards its sign. This extraordinary reversal is related to the sign of the 

 inactive tissue, and, when through a modifying agency this is altered, then 

 the sign of the active change may be similarly reversed. 



From the constancy of this relationship, Burdon-Sanderson inferred " that 

 the constantly operative electromotive forces, which find their expression in 

 the persistent difference of potential between the opposite (leaf) surfaces, 

 and those more transitory ones, which are called into existence by stimula- 

 tion, have the same seat, the opposition between them being in accordance 

 with the general principle that, whereas the property which renders a 

 structure capable of undergoing the excitatory change is expressed by 

 relative positivity, the condition of discharge is expressed by relative 

 negativity!' 



Between the first and second papers on Dionaea he had, whilst at University 

 College, London, pursued the same method of inquiry in the cardiac muscular 

 tissue of the frog. His investigations upon this subject are set forth in a 

 paper published in 1880 in the ' Journal of Physiology.' These researches 

 have been taken as a model for most subsequent work of this character, 

 whatever the tissue which has been utilised for such electro-physiological 

 investigations. The paper is entitled " The Time-relations of the Excitatory 

 Process in the Ventricle of the Heart of the Frog," and was followed three 

 years later by one " On the Electrical Phenomena of the Excitatory Process 

 in the Heart of the Frog and of the Tortoise, as Investigated Photographically." 

 In both these investigations he had the assistance of Mr. F. J. M. Page. The 

 whole research has been long regarded as classical, through the exactitude of 

 the methods of observation, the rigorous determination of the influence of 

 various surroundings or accessory factors, and the lucid interpretation of the 

 phenomena. It conclusively demonstrated that the diphasic effect (or change 

 of electrical sign) which is observed when two contacts are placed on the 

 uninjured surface of the frog's heart, is the algebraic sum of two monophasic 

 electromotive changes each of similar sign but developed successively one 

 under each of these two contacts. Hence it is not an indication of the 

 occurrence of opposite types of tissue change, but is simply the expression of 

 a similar type of monophasic change occurring at different times in different 

 localities. Finally, he demonstrated that the reason why the change begins 

 under one contact before it occurs under another one, is solely because 

 the excitatory state, like the muscular contraction, is propagated in the 

 differentiated cells which compose the cardiac tissue. For these researches he 

 was, in 1883, awarded a Koyal Medal. 



