42 Prof. J. Burdon-Sanderson. Relation of Motion in Animals 



We choose as our subject of observation a muscle of nearly sym- 

 metrical form — a band of parallel fibres. AVe explore its electrical 

 state, by a conducting arch containing a galvanoscope, the ends of the 

 arch being in contact with its surface. If the muscle is no longer 

 living, the galvanoscope gives no evidence of current. If it is living, 

 there is again no current, provided that the two surfaces are in the 

 same physiological state. If one is less living than the other the fact is 

 indicated by a difference of potential between them, a current flowing 

 through the galvanoscope from the more living to the less living. Vitality is, 

 therefore, here indicated by difference of potential. By vitality we 

 mean nothing more than the capacity for discharging function. This 

 capacity diminishes by discharge, i.e., by activity. Accordingly we 

 find that when, for any reason, the muscular substance at one part 

 becomes more active than the muscular substance at another, the former 

 becomes negative to the latter. 



Every observation of the electrical phenomena of muscle (or of any 

 other excitable structure) relates either to the state of capacity for 

 action (called in physiology "rest"), or to the state of action or dis- 

 charge. In either case it consists in comparing the states of two 

 contacts,* i.e., of two parts to which electrodes of a galvanoscope are 

 applied. It is obviously desirable for the investigation of the changes 

 at either, that those which take place at the other should be annulled 

 during the period of observation. On this consideration a rule is based, 

 to the mode of carrying out of which. I will advert presently. 



Most of the results which I shall place before you were obtained 

 with the aid of the capillary electrometer, of the use of which as an 

 aid to electrophysiological investigations I brought before the Eoyal 

 Society some instances nearly twenty years ago. Its application has 

 since been studied with great completeness by Mr. Burch, to whose 

 skill I am indebted for the instruments which I have used for my work 

 during the last ten years, and more particularly for the one which has 

 enabled me to submit to you the photographic results I am now about 

 to exhibit. These photographs, I need scarcely explain, express the 

 excursions of the meniscus of the mercury column as a sensitive plate 

 moves rapidly past the slit on which it is projected, each upward move- 

 ment of the image indicating that the surface of contact connected 

 with the mercury has become at that moment positive to the other. 



I do not propose to give this afternoon even the shortest description 

 of the instrument, and I should not occupy time in explaining why it 

 answers my purpose so perfectly, were it not that with the exception 

 of Professor Einthoven and Dr. R. du Bois-Reymond the leading au- 

 thorities on the other side of the Channel, and particularly Professor 



* It may be well to note that the contacts referred to here and elsewhere are 

 made by means of non-polarisable electrodes of the kind originally devised by 

 du Bois-Reymond and always used in physiological work. 



