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Georg Prochaska

Georg Prochaska (l749-1820); (first name sometimes referred to as Juri, Jiří or Georgius) was an Austrian ophthalmologist and physiologist from Blížkovice, Moravia. He studied medicine in Prague and Vienna, and from 1778 until 1791 was a professor of anatomy, physiology and ophthalmology at the University of Prague. In 1791 he succeeded Joseph Barth as professor at the University of Vienna.

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Prochaska was a pioneer in the field of neurophysiology, and is remembered for developing a comprehensive theory of reflex action involving the concepts of "vis nervosa" and "sensorium commune". Vis nervosa was described as a latent nervous force possessed in the nerves, and the term sensorium commune was defined as the point of reflection between the sensory and motor nerves.

Prochaska used the term vis nervosa as a direct analogy to Isaac Newton's "vis gravitans", because he believed that vis nervosa was an elemental form of energy, which could not be observed except through its effects such as reflexes and reflections, and adhered to natural laws that could be described (as could Newton's theories of gravitation), but at the same time were unexplainable.

Prochaska described the sensorium commune as the core mechanism of the reflex. It involved the spinal cord, medulla oblongata and the basal ganglia, and had the abililty to reflect sensory impressions into the motor nervous system by definite laws unique to itself, and also independent of consciousness. Prochaska demonstated that reflex worked without a brain, but could not work without a spinal cord, and summarized that voluntary behavior was a brain function, while reflex was spinal based.

One of Prochaska's better-known writings is Dissertation on the Functions of the Nervous System, which was later combined into one publication with John Augustus Unzer's (1727-1779) The Principles of Physiology, and translated and edited by English physiologist Thomas Laycock (1812-1876).