IEEE Technology and Society Magazine - December 2017 - 82

Physiology
The notion that living organisms can be considered in
some respects as machines has a long history, dating at
least as far back as Descarte's De Homine of 1643.
Nearly two centuries later Charles Bell drew analogies
between the biology of bones and internal organs on
the one hand, and engineered structures and systems
such as buildings, pumps, and pipes on the other. Herbert Spencer in the 1860s considered the way organisms maintain dynamic equilibrium, drawing direct
comparison with the steam engine, and also extended
such ideas to the equilibrium of non-living systems in
the natural world. At this point, although not made
explicit, notions about information emerged. In Germany, Eduard Pflüger (1877) addressed the importance of
feedback, using the example of the control of the dilation of the pupil, in a publication whose very title, "Teleological mechanics of living nature" anticipated the
classic "Behaviour, purpose and teleology" of the classic 1943 paper by Rosenblueth, Wiener, and Bigelow.
In a lecture published in 1879 Felix Lincke analyzed
mechanical regulation in general terms, and then applied
his ideas to the human body. Lincke distinguished
between the indicator (specifying the value of the parameter to be controlled), the modifier (valve, etc.), the transmission system (between indicator and modifier), and
the motor (to supply power for the actuation). In the
human body these functions were carried out by the eye,
muscles, and nervous system, for example. Information
flow was thus a key factor, as was feedback.
By the 1920s a number of German zoologists and
physiologists had taken up the study of biological control
processes. Jacob von Uexküll (1864-1944) and Richard
Wagner (1893-1970) both considered the rôle of feedback. Von Uexküll used what we would now term signal
flow diagrams to represent both internal feedback loops
and the relationship of the organism with its environment,
while Wagner explicitly discussed biological feedback.

FIGURE 1. The opening of Pflüger's publication.

Both authors also applied biological ideas to society. Wagner was the anonymous author of a short 1932 publication entitled Unemployment and Deflation in the Body
Economic from the Point of View of Biological Laws, in
which he proposed solutions to the economic crisis based
on biological metaphors including feedback.
Let us turn now in a little more detail to the contributions of these early German thinkers in this area, contributions which mark the beginning of the application of
information ideas to biological and social systems.

Eduard Pflüger (1877)
Pflüger studied medicine at the Marburg and Berlin,
becoming professor of physiology at the University of
Bonn, where he remained for the rest of his career. He
made contributions to many branches of physiology,
and also conducted research into neurology, metabolism, and the regulation of body temperature. Such
research made him think naturally in systems terms
about a living organism and general biological regulatory functions. In particular, Pflüger considered the control of the dilation of the pupil in a publication entitled:
"Teleological mechanics of living nature."(See Figure 1.)
With great foresight Pflüger noted: "the need here is
for the correct degree of excitation of the optic nerve, in
the way most suitable for acute perception. Thus the
excitation of the optic nerve itself must control the
width of the pupil" [2]. This is particularly important as it
was one of the earliest papers to identify information
flow in an implicit biological feedback loop.

Felix Linke (1879)
Linke was Professor of Mechanical Engineering at the
Polytechnikum Darmstadt. Otherwise, little is known of
him. In 1879 he gave a lecture, subsequently published
[3], in which he explicitly compared the workings of the
human body to elements of the control systems that
were becoming so important in mass production in the
industrialized countries. In terminology remarkably similar
to that of modern control engineering, he distinguished
between the "indicator," "modifier," "transmitter," and
"motor" - very much as we would now talk about sensors, controllers, and actuators.
Figure 2 shows Linke's identification of the heart,
lung, stomach, brain, sensory organs, nerves, and muscles in a stylized, almost "proto-cybernetic" form. He
went further:
The difference between our voluntary actions and
the operation of a machine is only quantitative.
The reliability and effect of [our biological]
organs, or a combination thereof, simply contrasts with the absolute express and undisputed
result of a machine.

IEEE TECHNOLOGY AND SOCIETY MAGAZINE

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DECEMBER 2017

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