Puls Maschine Labor EmpfindlichkeitAnja Breljak
What if the digitised object is not static, inanimate, supposedly fixed in space and time, a thing, but a breathing, pulsating body? Something that lives, that is fleeting, that changes every moment? How does the machinic capture modify what is perceived as a body? And what does it take to machinize the body and its movements in the first place? An investigation.
According to legend, when Galileo Galilei, who had taken up medical studies in Pisa around 1580, observed the swinging chandeliers in the local cathedral, he discovered the law of the pendulum. This discovery is also legendary because it provided the precondition for the first accurate pendulum clock, i.e. the first precise clock ever, and perhaps also anchored something like the idea of an objective time in the thinking of modern Europe. To determine the duration of the pendulum's movement, Galileo, in the absence of a timepiece and as had long been customary among natural scientists, used his own pulse. However, the astonishing regularity of the pendulum's motion, which he had just established through the regularity of his pulsating body, neatly discredited this conventional means of time measurement: for now, suddenly, with the astonishing regularity of the pendulum in view, the irregularity of the pulse had become evident, which is said to have prompted Galileo to turn the idea of time measurement around and instead to determine the pulse by means of the uniform motion of the pendulum, for the benefit of medicine. This reversal of the way of looking at things also set in motion a readjustment of perception: the movement of the pendulum, which could be translated into a physical law because it was regular, determined and therefore calculable, now made it possible to measure the contingency of the pulse, its situational responsiveness to the environment or condition of the living body, which had been tolerable until then. The pulse was suddenly too imprecise, dependent, an expression of all the unpredictable effects on the body. The pendulum thus also paved the way for tracking down the reasons for the contingency of the pulse by means of precise machines.
It was the inventor and physician Santorio Santorio who put Galileo's idea into practice when he invented the pulsilogium in 1625 at the latest. This is an instrument based on the pendulum for measuring very small changes in the pulse that escape the senses of the physician. It was Santorio, incidentally, who modified the Galileo thermometer so that it could be put in the mouth - just one of many larger and smaller devices in the slowly growing machinery of evidence-based medicine.
However, it should be noted that even the precision of pulse measurement with the pocket watch commissioned by John Floyer around 1707, which he had made specifically for measuring the pulse, was still based on the medical practitioner using the sense of touch to feel and count or record the pulse. The tactile (self-)touch by a human being remained the basis for making sense of the pulse; the machine was only an accessory.
Human touch, as it had long been handed down and indispensable in the art of feeling the pulse, received extensive competition from machines with the emergence of physiology as an exact natural science at the beginning of the 19th century. Physiology relied on the experimental investigation of both animal and human bodies and their nerve pathways, their modes of reaction, all kinds of substances, intrusions and stimuli, in order to find out something about their commonalities and specifics in this way, in order to mathematically-physically measure the living. This required the »search for reliable objective characteristics through the application of chemical, physical and physiological techniques«, as Karl von Vierordt, physician and professor at the first independent chair of physiology in the German-speaking world, put it in his theory of the arterial pulse in 1855. The ancient art of feeling the pulse, whose history can be traced back at least to 7th century BC China, was to be turned into a modern science of pulse counting and recording. And for this purpose, according to Vierordt, a reliable objectivity was needed, and that meant: a technical externalisation, not only of time, but of feeling itself. This externalisation of feeling, however, had to be just as sensitive to the process of pulsation as it had to be insensitive to other processes - such as breathing, vibrations, noise, lack of concentration, distraction, and so on. For this purpose, Vierordt designed a technical device, a machine for the precise measurement and direct recording of the pulse, which he called the »sphygmograph« and described as follows:
If the plate p of the sphygmograph is placed on a superficial, not too small artery, each expansion of the artery corresponding to the cardiac systole raises the lever arm I upwards, while it sinks when the artery contracts. The end of I thus describes a circular movement which, for the same pulse size, increases the closer the application point of the pulse is to the fulcrum h of the lever. If the hair were simply attached to the other end of the lever arm I, the tip of the hair would have to move away from the paper even with only insignificant deflections of the lever arm, so that the pulse movements could not be properly written down on the paper [...]. The examiner, who can stand, sit or lie down, places the arm horizontally under the plate p in such a way that the longitudinal axis of the arm is perpendicular to the rod A. Since the pulse must necessarily be recorded many times enlarged, it is essential that the arm remains still during the experiment [...].
Vierordt's explanations make it clear that under the more than complicated application of the measuring instrument, which had to take into account many subtleties and interfering factors, the now approximate art of feeling the pulse was transformed into an exact »technique of pulse examination«. This was based on the simple fact that the living body can also be understood in its actual »pulse mechanics«, i.e. it represents a physical event that can be experimented with and measured quantitatively. The pulse could thus be recorded and calculated, and normality and regularity could be precisely distinguished from deviation and change. What until then and for centuries had had to be expressed semiotically through images, metaphors and descriptions, integrated into taxonomies and narratives, could now be represented in numerical series, diagrams and curves.
The basis for the diagrammatic transformation, in which the pulse beat became a curve and produced evaluable series of numbers, is a translation process that is worth dwelling on briefly: the small plate p, of which Vierordt writes, passes on the very fine movement of the pulse via a »feeler lever«, and thus sensomechanically, to a kymograph, a device that inscribes the movement of the feeler lever on sooty paper as a track. The paper in the kymograph, in turn, is mounted on a rotating drum that must be driven as smoothly as a clock, for instance by means of a spring motor. In this apparatus, three translation processes take place: a sensomechanical one from the pulse to the platelet, a mechanical one from the platelet to the lever, and a graphic one from the lever to the rotating paper. The result is a paradoxical immediacy: because 'only' technology is interposed, and not the human sense of touch, now discredited as unreliable, because the result is a standardised representation that is largely immune to chance or subjectivity, which can be experienced visually and calculated precisely, the sphygmograph comes a little closer to nature. In the face-to-face of the doctor with the patient, which functioned via a finger-to-hand, a sensomechanical-graphical machine infiltrates, which becomes the anchor point of a different kind of conversation: A rarely conscious, 'only' tangible, very fleeting bodily process suddenly becomes apparent for all present (and even for the future), becomes a point of reference, even opens itself up to (self-)comparison. While it may still be necessary to evaluate and discuss the implications of the curves, the authority of the word now hangs on the aegis of the curve and thus the number. And Vierordt emphasises that the sphygmograph is by no means only good for examining pulses, but also respiratory movements, heart movements or even »the movements of the cerebral membranes etc. must be easily recorded graphically by means of the sphygmograph«, a trend that had long since begun with modern physiology and had thus found its medial principle, on which Étienne-Jules Marey, among others, was then able to build and further develop in a smaller, more manageable, more refined way. Vierordt was also by no means the first to dare to invent a technical device for recording the pulse. He was preceded by a series of experiments that can be traced back to ancient Greece and hint at a violent tradition of hair-raising experiments, vivisections and torturous animal testing.
The sphygmograph as an exemplary innovation for systematically getting closer to physiological events can be used to study the sensitisation of media technologies. Only in the combination of a recording device - the kymograph, which Carl Ludwig had already used for his first physiological experiments in 1846 - and the idea of pressing a small brass plate directly onto the artery (and not inserting a glass tube into it, as Ludwig apparently still did) did a reliable device come into being. Its clou consists in the use of a sensor, namely the simple brass platelet p, which, through the way it is integrated into the apparatus, acquires a specific sensitivity for fine mechanical movements and thus becomes the decisive interface between the fleeting bodily process and its recording. It is only through the appropriate sensory element that the possibility arises of translating the otherwise fleeting, non-conscious and above all situational process of the pulse beat into a curve directly at the moment of occurrence, and this in real time, without having to damage the body or hinder the process.
Three important shifts result from this machinic arrangement of body process, sensor and recording apparatus: firstly, the sensor makes it possible to ensure a subjectless link between body process and media technology that appears neutral, leading to an independence of the measuring instrument. If the art of feeling the pulse was also characterised by numerous aids - be it breathing techniques, counting aids, amounts of water or mechanical watches - now the processes of feeling, sensing and recording can be taken over by a device that only needs to be used correctly and whose recording needs to be interpreted. From now on, and with all the further inventions that add other sensory components to the kymographic recording, training on the device is required. The human component only frames the process of measurement, it ensures the application of the instrument and the interpretation of the results. However, even the humanless recording by the machine still needs humans, as mediators, to operationalise the machine. But it now releases them from their subjective dependence on their sensory sensitivity, because the machine becomes the guarantor of objectivity.
Secondly, something is taking place here that could be described, following Joseph Vogl, as a »denaturation of the senses«. This does not necessarily mean the replacement of the human ability to feel by an apparatus with a sensor, but above all the computerisation of the sensed process. The sensory translation is a transmission; here, an event becomes a signal and can be represented as a mathematical function, which can be shown as a series of numbers, a curve or a diagram. In Vierordt's reflections on his results, however, it becomes clear that it is the sense of sight that retains sovereignty over the medical fact, simply because it can grasp with a glance everything that deviates in the series of numbers or in the curves.
Thirdly, this also works against a change in the culture of sensibility: Whereas previously an introduction to the art of feeling the pulse was necessary, one's own sense of touch had to be refined, the right moment had to be found, the interpretation had to be learned, now it is a matter of reading out the application, the correct handling of the apparatus and the recognition of deviations from the standard curves and numbers. The focus is no longer on the body, even if it is in the form of one's own body as a medium, but on the apparatus and its result. From touching to applying, from traditional knowledge to dedicated know-how, which can know smaller and finer differences without having to take into account the medical practitioner's sense of touch, while presupposing the careful handling of the sensitive apparatus.
Vierordt's research into bodily processes and his inventions for measuring them were important for the emergence of physiology as a science, but they were in the context of a comprehensive flourishing of experimental bodily research, especially in the German-speaking countries of the 19th century. Machines and instruments of all kinds emerged to measure movement, force, nerve stimuli, to record and scientifically determine sight, touch, smell, hearing and feeling. It was no coincidence that this development coincided with the beginning of the age of the laboratory. In the laboratory setting of scientific research, the laws of physics, chemistry and biology could be empirically addressed, and the measuring instruments, tools and machines were no longer merely stored and collected to be brought out for demonstration purposes. The laboratory created an instituted space for the actualisation of knowledge wrested from nature and tickled out by experiment. Here, substances, equipment and machines, organisms and organs, procedural knowledge and the craftsmanship of many hands could come together to create facts in situ. The laboratory was thus also the place where knowledge was achieved through the skilful arrangement of subjective experience with those objective technicisms of which Vierordt was so convinced. Of course, this required an arrangement in the literal sense that could bring the bodies in the room into a suitable rhythm with the equipment and experimental objects. Justus Liebig's chemical laboratory in Giessen, for example, which was set up in 1839, indicates how central it was to distribute the experiments over different tables and to spread the tables around the room in order to allow both division of labour and accessibility. In Carl Ludwig's Leipzig laboratory complex, which opened in 1869 as the Physiological Institute and of which floor plans were even made, the separately linked complexity of the room structure becomes even more apparent: microscopy, work with mercury, vivisections now have their own rooms, the storage of birds, fish, rabbits, dogs and horses takes place in the annex and in the cellar. Everything gets its designated, demarcated place in neighbourly proximity, while people move from table to table, from room to room, putting equipment into operation, making records, bringing experimental objects, substances or material into place. The laboratory begins to pulsate with its own rhythm.
The laboratory aimed to create controllability, to exclude disturbances, to minimise the noise of everyday life for the researching bourgeois elite. Animals were given their place away from the concentrated research so that their calls and movements were not distracting. Helpers had to move unnoticed from room to room, for example to stoke the fire, procure materials or tidy up. Children were not allowed in, and for a long time women were only used as demonstration or experimental objects. The same applied to people with disabilities, from poorer classes, from maternity or orphanages, prisoners or inmates of closed institutions, and People of Colour, especially in the so-called colonial territories - the laboratory revolution of the 19th century brought with it a surge in animal and human experimentation, in which the disenfranchisement of living beings was increasingly exploited and justified by so-called scientific progress. The laboratory was thus not only a place of exclusion, the laboratory was also that institution that placed a logic of research above the welfare of living bodies and began to trait them with its substances, devices, procedures and machines. It was only here that a largely controlled environment could be created to investigate the supposedly endogenous differences of sensory, neurological, motor or immunological capacities of different groups of living beings or to find their commonalities. And this required appropriately sensitive instruments that objectified and justified the measurements, that potentiated the observation, and the handling of the instruments had to be carefully trained to apply them to the bodies. The laboratory was the space where training and potentiation of the sensitivities of instrument and researcher could take place, while exploiting the sensitivities of the animal and human bodies being researched. Here, in this paradigmatic place of Western modernity, an equally paradigmatic subjugation of the sensitivity of the body to a new, machine-borne culture of sensibility took place.