Workshop 2: Henning Schmidgen, The Interval as Event: Helmholtz's Physiological Time Experiments

Henning Schmidgen (Max Planck Institute for the History of Science, Berlin) opened his paper with a brief introduction of his position and field of expertise. Schmidgen, as a Berlin-based historian of science with a background in psychiatry and Deleuzian philosophy, voiced a special interest in the history of the experimental life sciences of the 19th and early 20th century. He explained how he is currently finalizing a larger project concerning the history of short time measurements in physiological and psychological laboratories, roughly between 1850 and 1930. Schmidgen described how the corresponding time experiments are well-known under the name of ‘reaction time measurements,’ and they have a routine existence in contemporary neurophysiology, brain research, psychology, and more broadly the cognitive sciences. He followed in arguing that the emergence and evolution of physiological and psychological short time measurements is intrinsically connected with the advent of social and cultural modernity.

Henning Schmidgen explained that in his historical work he deals with the emergence and evolution of these experiments, with a focus on the material culture of scientific practice, that is the instruments that were used for measuring these extremely short time intervals (e.g. electromagnetic chronoscopes), the inscriptions that were produced in this connection (e.g. traces of tuning forks), and, more generally, the images that came out of and referred to this kind of practice, in particular schemes (or diagrams) of experimental setups. Schmidgen started by introducing first image—showing the experimental arrangement or research machine that the German physiologist Hermann Helmholtz used in the early 1850 to measure the propagation speed of the nervous impulses in frogs. These, as the first time experiments of this kind ever done, Henning Schmidgen positioned at the centre of his presentation.

He argued that the emergence and evolution of physiological and psychological short time measurements (or, in short, ‘psycho-physiological time measurements’) is intrinsically connected with the advent of social and cultural modernity. One the one side, the corresponding experiments relied, in their materiality, on technologies of acceleration, in particular the steam engine and the telegraph; on the other side they were part of deceleration strategies that are equally characteristic of modernity  – think of the museum and photography. Schmidgen proposed that in some sense, these experiments aimed at slowing down physiological and/or psychological processes, i.e. to render them observable and above all repeatable. Repetition, however, proved to be quite complicated, since technologies were not as reliable as they are today, experimental milieus were not as stable as they are now, and standards of precision were only starting to be defined, distributed, and adopted.

To illustrate his arguments, Henning Schmidgen presented one of the case studies that he has conducted in the framework of his larger project. In the center of this case study stands an experiment devised and carried out by Hermann Helmholtz, one of the luminaries of 19th century science. Helmholtz is famous for his contributions to the experimental physiology of seeing and hearing, his work on standardizing theoretical and practical physics as well as his epistemological writings. Schmidgen focused on his early work in experimental physiology, in particular his measurements of the propagation speed of nervous impulses.

Henning Schmidgen argued that traditional history of science often presents these measurements as a decisive achievement of 19th century physiology. The French physiologist Charles Marx even went so far as to say that these measurements constitute the first contribution to the science of physiology since antiquity, i.e. since Aristotle. Schmidgen aimed not to criticize or deconstruct this kind of historiography but to look at Helmholtz’s psycho-physiological time experiments from a Deleuzian point of view.


Henning Schmidgen used four aspects of Deleuze’s event:

First, the event as encounter, as shock. Here, Schmidgen made a connection to Charlie Gere’s and Bron Szerszynki’s position paper: “For Deleuze the event is the word he uses to describe instantaneous productions intrinsic to interactions between various kinds of forces” – or partial objects.

Second, the event as located or situated, as emerging and taking place in the empty time between two instants. This is the event as interval. Schmidgen argued that, Helmholtz’s time experiments offer a slightly different perspective on this: they actualize the interval as event, i.e. as the time span between stimulation and contraction and/or reaction. In Helmholtz’s experiments, this interval appears as a highly remarkable, perhaps even enigmatic phenomenon, a scientific fact that refers back to a specific laboratory assemblage producing effects which can hardly be defined by single scientific concepts.

And third, the event as a quasi-poetic entity, as different from an object, a thing, or a signified. The event as something eccentric, de-centered, even wacky. As Schmidgen explained, Helmholtz, when presenting the findings of his time experiments was confronted with the problem to explain what exactly he had measured and what the meaning of these measurements were.

Fourth – the event as a profoundly problematic entity. By this Schmidgen did not mean the event as a riddle or as simply enigmatic but rather as general answers to problems that, in their concreteness, remain to be posed. In fact, Helmholtz’ measurement defined a diagram of experimentation that, in radically altered technical and scientific landscape, is still functioning today.


Henning Schmidgen began by looking at the encounter of elements, or in other words the event, that is the basis for Helmholtz’s time experiments. Schmidgen described how for his pioneering investigation of the propagation speed of nervous stimulations in the frog, the physiologist, then based in Königsberg, devised an experimental set up consisting of two interconnected electric circuits, one to stimulate a nerve-muscle preparation, the other to measure the so-called current time by means of a galvanometer, i.e. a device for measuring current intensity. He then proceeded in illustrating his example and argued that the encounter which allowed Helmholtz to carry out his time measuring experiments was basically an encounter between electromagnetic telegraph and timing technologies and nerve muscle preparations, a coupling of machine and organism – similar to what Deleuze and Guattari have described, in Anti-Oedipus, as “machines,” i.e. as local and temporary installations combining “really distinct” parts in order to create economic effects in the most general sense. However, on the level of experimental practice, Schmidgen pointed out, this machinic coupling extended into an dynamic assemblage that, in its complexity and distributedness, went far beyond what the scheme here illustrates. He argued that, what the scheme fails to picture is the human observer who, in order to read off the deflections of the galvanometer with sufficient precision, had to use a telescope, a mirror and an external scale. Helmholtz, had to look out for methods that could serve to measure muscle performance and since duration was a crucial factor in this, he eventually decided to use electromagnetic precision timers, or rather to adopt these timers for the specific purposes of physiological research, Schmidgen described. However, the result was a considerable increase in precision and a new problem: where should the muscle be stimulated if one wanted to obtain reliable results (in the middle, on top, or somewhere close to the point close to the corresponding nerve)? And further: if one decided to go for the nerve, would the performance of the muscle change when the stimulation was done in different places in the nerve?

Henning Schmidgen argued that it was here that the research interest of Helmholtz underwent a significant shift: it not only went from the graphic method to electromagnetism, but also from muscle activity to nerve activity. In linguistics terms, one could speak here not of a floating signifier, but a floating signified. Henning Schmidgen argued that in the thick materiality of the experimental process that Helmholtz was involved in the object of his research changed in rather unexpected or, to speak with Hans-Joerg, unprecedented ways.


Henning Schmidgen then moved on to the second aspect of the event, its connection to the interval. He described how toward the end of their book “What is philosophy?”, Deleuze and Guattari speak about the temporality of the event and in a seemingly paradoxical move, locate the event in the empty time lying between two moments or actions: “The meanwhile [the French expression is “entre-temps”], the event is always a dead time; it is there where nothing takes place, an infinite awaiting that is already infinitely past; awaiting and reserve” (p.158).

Schmidgen argued that in Helmholtz, the relation of interval and event is somewhat similar, except that the event is not tied to the interval. To the contrary, it is the interval that is the event. In fact, Schmidgen pointed out that, Helmholtz experiments are the one of the earliest instances of defining and precisely measuring the span between stimulation and contraction, sensation and movement, thought and action. Schmidgen illustrated this with respect to Helmholtz’s experimental set up. He argued that, so far we have only gotten a rough idea of how Helmholtz could measure the time between that was needed for the contraction of a muscle stimulated from a specific point on the nerve, and that we need to know more about his way of proceeding if we wanted to understand how he measured the propagation speed of nervous impulses. Henning Schmidgen argued that the solution is rather simple: you do repetitions and introduce differences. First, you measure the time span between the stimulation and the muscle contraction, when stimulating a specific point on the nerve. Then you do the same thing again, but you change the position of electrode on the nerve. From the difference in the time spans you measured in both runs and the corresponding distance between the positions of the electrode on the nerve, you then deduced the propagation speed of what was later called the “nervous impulse.”

Henning Schmidgen illustrated how this way of proceeding, that was later called the variation and subtraction method, opened up a whole field for possible investigations. In fact, Helmholtz applied the same method in his experiments with human beings: “At some limited point of skin […] a very weak electric shock” was applied to the experimental subject. The subject was asked to react to the sensation as quickly as he or she could by means of “a certain movement of the hand or the teeth.” Then, a different point of skin was chosen, again a light shock was given, reactions followed and were measured. From the difference in measurements for the big toe and the neck (or the finger and the throat), Helmholtz deduced the absolute speed of the propagation of the stimulation in the sensible nerves of human beings. This deduction was based upon the assumption that the only difference in the various series of experiments consisted of the position of the electrodes on the surface of the body. All other factors—the stimulations themselves, the functioning of the measurement instruments, the identity of the conduction speed in the sensible and motor nerves, even the transposition of sensations into movements—were deemed by Helmholtz to be constant. For example, when estimating the time required for the cerebral processes involved (according to Helmholtz, 1/10 of a second), he explicitly underscored that “the duration of the processes of perceiving and willing in the brain does not depend upon the place on the skin at which the impression is made.” Otherwise, Helmholtz could only argue that, within single series of experiments, he had found a “sufficient agreement” of results. What remained constant then, was nothing but the “sums” of the measured times. How these sums were constituted remained largely obscure.

Henning Schmidgen explained that the conceptual distinctions Helmholtz suggested in order to break down the reaction process into its components were accordingly weak. In the few published lines he devoted to his experiments with human beings, Helmholtz spoke of the “sending of the signal,” i.e., the propagation of the stimulation in the sensible nerves, the processes of “perceiving and willing in the brain” and the transmission of the “message” through the motor nerves to the muscles. The general term that Helmholtz introduced for these components was “Zwischenzeiten”, i.e. inter-times, “entre-temps,” or meanwhiles. The basic claim he wanted to make by referring to these inter-times was that experience and behavior were essentially discontinuous processes, perforated as it were by wholes, gaps, and interstices.


Thirdly, Henning Schmidgen referred to the event as a quasi-poetic entity, not a thing or tangible product, but an incorporeal and almost enigmatic occurrence, a conceptual modality. Schmidgen argued that when Helmholtz presented the results of his experiments to the larger public, he ran into difficulties. From his perspective, there could be hardly any doubt that the propagation of simulations in the brain and nervous system took place at a comparatively low speed (i.e. 60 meters per second). At the same time, it was obvious that this was a fact that was not accessible to the common sense or even attentive self-observation. As Helmholtz put it in a popular lecture delivered in Koenigsberg in 1850. With respect to the time required for transmitting sensations from the periphery of the body to the cerebral center, he had to admit: “we have never experienced anything similar” (p.321). Helmholtz mentioned some interesting feature in the experience and perception of time, e.g. the lack of synchronicity in acoustic and visual perceptions, when a canon fired at a distance, or the fusion of images when a piece of glowing iron was rotating in the dark. However, Henning Schmidgen argued that, all these examples did not really illustrate the fact that within the living body the propagation and transmission of stimulations required time. Perhaps one should even say that these inter-times were impossible to experience because, in some sense, they were at the basis of all experience. To speak with Helmholtz, they were residing in region where “the expression of our own experience can give us no information” (p.321) – in a kind of physiological apriori, a cerebral and nervous unconscious that merely was accessible to precision time measurements and insofar firmly tied to the “other scene” of the laboratory.

Henning Schmidgen illustrated how at this point, the new science of physiology returned to the much more traditional knowledge of anatomy. As Helmholtz explained at the end of his talk, the “Zwischenzeiten”, the inter-times that he had measured were not obvious to our everyday consciousness, because they were deeply tied to the form of the human body: ”Happily, the distances are short which have to be trasversed by our sensuous perceptions before they reach the brain, otherwise our self-consciousness would lag far behind the present.” And he added a rather poetic reflection: “With an ordinary whale the case is perhaps more dubious; for in all probability the animal does not feel a wound near its tail until a second after it has been incited, and requires another second to send the command to the tail to defend itself.” (p.325).


In conclusion, Henning Schmidgen argued that Hermann Helmholtz’s psycho-physiological time experiments paved the way for uncounted investigations concerning the time relations embodied in the brain and nervous system. In the 1860s scholars such as Adolphe Hirsch and Rudolf Schelske tried to reproduce the findings of Helmholtz, without much success. A decade later Franciscus Donders and Wilhelm Wundt, one of the often quoted founding fathers of experimental psychology, adopted the basic scheme of Helmholtz’s experiments while retooling the entire set up with new instruments and inscription devices. Following up on Wundt, the Würzburg school started to question the role of the test person in reaction time experiments and suggest to do away with sound proof rooms and other artificial laboratory stuff in order to investigate the temporal dynamics of the thought process. In his unpublished seminars, Deleuze refers to the fascinating work of this research school. In the 1940s cyberneticians such as John Stroud came back to the Wundtian approach and eventually scholars such as Benjamin Libet translated the time lag experiments into our contemporary techno-scape. Henning Schmidgen argued that he is referring to these facts not because he sees the history of the Helmholtz scheme as a teleological. Schmidgen point was not so much that Helmholtz, by means of his experimental practice, has created a problem that is still with us. In Henning Schmidgen’s understanding he has offered something like (an event) a general solution to problems that, in their concrete form, still remain to be posed. And in this sense, Schmidgen claimed that his interval experiments have created an event.



Firstly, debate focused on the idea of the telegraph network as a nervous system. IT was recalled that by 1850 an explicit technological reference came into being, in terms of the connection between the graphical matter and steam engine technology.


Secondly, two experimental cultures - social and scientific – were compared. Scientific tradition was described in terms of signal processing and translating the life to accountable measurement (time moments, discrete moments). On the contrary, the social experiment was framed as that which sticks to continuous non-measurable model. The split between those two kinds of experimental aesthetics was outlined in terms of obvious differences as well as similarities:  Henning Schmidgen’s example shows how reaction of the public, forces experimentators to turn to different methods to make the same point again, in a publically acknowledged way.


And finally, crafting of Deleuzian account of an event and Helmholtz’s analysis were compared. Subsequently, the following questions were posed:

  • How such an account would allow us to identify the singularity of an event?
  • How to distinguish between the ordinary and singular?
  • How going through the interval encounter that highlighting of singularity occurs?
  • How singularities and events are related?

It was agreed that two terms are necessarily the same thing and this kind of research as event, poses danger in terms of a reproduction of very traditional accounts. It was also emphasised that by performing the experiment and publishing its findings the whole branch of research has taken a different path. In conclusion, it was decided that the difficulty is more the case of coming up with an interesting and convincing account of the moment of transformation that spells it out on the level of materiality/practises and does not reduce it to the history of a male genius that comes along and invents something.