AucustT 10, 1899] 
NATURE 
343 
THE RELATION OF MOTION IN ANIMALS 
AND PLANES TO THE EELEGPRICAL 
PHENOMENA ASSOCIATED WITA IT? 
HE lecturer began by observing that the proper 
subject of the Tecture being “ the nature or laws 
of muscular motion,”? he would discuss the chemical, 
mechanical and electrical concomitants of this most im- 
portant function with a view to the elucidation of their 
mutual causal relations. He would, however, ask the 
attention of the Society chiefly to the electrical pheno- 
mena which are associated with muscular action, as being 
those which he had himself specially studied. Some 
points relating to the mechanical effects of muscular 
action must be referred to by way of introduction, inas- 
much as it is by these that a muscle performs its function 
as an organ of motion. There were two ways of in- 
vestigating these effects experimentally. We might 
observe and record either the change of form which a 
niuscle undergoes in response to a stimulus of very short 
duration when contracting isotonically, z.e. as it does 
when lifting a weight, or the increase of tension which 
occurs when it endeavours to overcome a resistance, 7.2. 
when it acts isometrically. It was shown that although, 
as regards an entire muscle, the isometric method was 
preferable to the isotonic, the time occupied by a single 
element of muscular structure when directly excited in 
developing its maximum tension (2.2. in the transform- 
ation of chemical into mechanical energy) could be best 
estimated under isotonic conditions. He then proceeded 
to describe his own method of accom- 
plishing this measurement with the aid 
of photography. It consists in observing 
the change of form of the surface of a 
living muscle when a single break in- 
duction current is led through it in such 
a way that the observed surface is at the 
kathode. A magnified image of the kath- 
odic electrode, which moves freely with 
the muscle, is projected on a slit behind 
which a sensitive plate passes, and in this 
way a curve is obtained from which the 
time-relations of the movement can be 
deduced. It is thus learned that at the 
kathodic spot, Ze. at the spot immedi- 
ately excited, the process attains its 
greatest activity before the end of the first hundredth of 
a second. The importance of this datum consists in its 
bearing on the question whether or not the electrical 
change by which the change of form thus observed is 
accompanied is coincident with it, follows or precedes it. 
The answer to this question could not, of course, be given 
until the time-relations of the electrical change had been 
considered. These were discussed as follows :— 
The essential point in investigating the electrical 
changes which occur in muscle is to connect two parts of 
its surface through a galvanoscope. The general result 
of such an exploration is (1) that similar parts in a similar | 
physiological state are equipotential ; (2) that between 
similar parts which are not in the same state there is 
always a difference of potential, measurable by the 
method of compensation, the less capable of function, z.e. 
the less living, being negative to the more living; and 
(3) that transitory differences of potential arise between 
two parts of the living surface when the one is excited to 
discharge of function, the other remaining at rest. Thus 
the state of rest or fitness for function of a part is denoted 
by relative “positivity,” discharge of function by relative 
“negativity.” ? 
1 Abstract of the Croonian Lecture, delivered before the Royal Society, 
by J. Burdon- Sanderson, M.A., M.D., F.R.S., on March 16. 
2 See ‘‘ The Record ”’ of the "Roy yal Society, 1897, p- 126. 
% The use of these words in the sense above stated has been strongly 
objected to. It is difficult to see to what obscurity of meaning it can give 
rise. ‘‘ Negativity 
velatively to another surface. 
NO. 1554, VOL. 60] 
First Fundamental Experiment——The effect of an 
excitation which is instantaneous and so localised as to 
affect in the first instance only one of the two surfaces of 
contact is the sudden manifestation of a difference of 
potential between them, this effect being momentary 
(case 1) or continuous (case 2) according to the duration 
of the excitation. In either case it is designated “ex- 
citatory variation” if the muscle is referred to, ov “ action 
current” if the galvanoscope is referred to! If the 
capillary electrometer is used as galvanoscope, and its 
excursions are recorded photographically, the curves so 
obtained truly and faithfully express to us the character 
and time-relations of the varzation, provided only that 
we know according to what rule they are to be in- 
terpreted. This rule can be deduced from the well- 
known properties of the instrument, as has been fully set 
forth elsewhere.” We may, however, interpret the photo- 
graphic curves we obtain in the exploration of living 
muscle by comparing them with counterparts photo- 
graphed under previously determined and known physical 
conditions. Thus by arranging our physical experiment 
so as to reproduce the hypothetical conditions of our 
physiological one, we may prove the truth of our hypo- 
thesis by the coincidence of the two results. And inas- 
much as the two cases, z.e. the two forms of “ variation,’ 
above referred to, are the only ones that present them- 
selves, provided that we adopt a mode of procedure to be 
presently explained, there is no difficulty in applying this 
purely empirical procedure. 
Fic. 1.—Photographic curve of diphasic variation of sartorius muscle. 
of plate indicated by distance accomplished in 1/ro sec.; moment of excitation by 
vertical (radial) line. 
| surfaces in consequence of stimulation of one or both of them. 
” of a surface means nothing more than it is negative | 
Rate of movement 
The first fundamental experiment is one in which a 
curarised muscle of simple structure (z.e. one which con- 
sists of a band of parallel fibres) is subjected to the action 
of an instantaneous stimulus applied to it near one end, 
as shown below. ‘The result is that a wave of excitation, 
p a 
a 
of which the progress is marked by mechanical and 
electrical changes, passes along each fibre (represented 
by the black line), starting from the seat of excitation 7, 
and affecting first the nearest contact Z, and after an 
interval the more distant contact ¢@ The photograph 
(Fig. 1) is the curve obtained under these conditions. 
But if, as above suggested, we proceed in such a way 
as to limit the observation to what happens at one 
contact only, and for this purpose camce/ the effect at the 
further contact d, and repeat our photographic observ- 
ation just as before, we find that the curve has 
assumed an entirely different form shown in the 
photograph (Fig. 2). [As in both photographs, the 
movement of the sensitive plate is circular, the ordinates 
are polar, and must be measured accordingly.] Before 
the effect at @ was cancelled, the curve had the form 
shown in Fig. 1. We therefore conjecture that the 
1 Here again our language has been objected to. ‘‘ Excitatory variation” 
means the coming into existence of a difference of potential between two 
translation of the German word “© Reizschwankung.” reyeie 
2 Journal of Physiology, xxiii. p. 325. 
