Georg Prochaska

Background

Georg Prochaska was born on April 10, 1749, in Biizkovice, Moravia, the son of a smith and smallholder. Two of his older brothers also became smiths.

Education

In his early years, Prochaska, being thought too weak physically to work at the forge, was sent to the Jesuit Gymnasium at Znojmo. When Prochaska’s father died in 1763, the family was left with little money to support his further education, but a nearly fatal accident (in which he was poisoned by fumes from a leaking stove in his room) brought Prochaska to the attention of the wealthy parents of his schoolmates. He was thereby offered the opportunity to become a private, paid tutor, which enabled him to remain at the Gymnasium. Prochaska continued to study philosophy at Olomouc from 1765 until 1767, then went to Vienna, where he studied medicine from 1770 to 1776.

After Prochaska went to Vienna, he won the patronage of Anton de Haen, to whose clinic he had been taken, critically ill and unable to pay for treatment; de Haen recognized his skill in anatomical drawing and engaged him as an assistant in his department of clinical teaching.

De Haen died before Prochaska had finished his studies, but Prochaska found another supporter in Joseph Barth, the cultivated but eccentric professor of anatomy, who gave him an assistantship and taught him his methods of blood-vessel injection and his operation for cataract.

Career

In 1778 Prochaska was appointed a professor of anatomy and ophthalmology at the University of Prague, where from 1786 he also taught “higher anatomy,” physiology, and ophthalmology. In 1791 he returned to Vienna as Barth’s successor as professor of anatomy and ophthalmology. He remained in that post until his retirement in 1819.

Prochaska began his own anatomical and physiological research while he was still a student. In 1778 he published his first treatise, on certain questions concerning the strength of the heart and the movement of blood through the blood vessels, entitled Controversae quaestiones… In this work, Prochaska demonstrated, through physical models, that the velocity of the blood diminishes as it passes from larger to smaller vessels, in proportion to the increase in the sum of the cross-sectional area of the branches.

The treatise provoked a violent reaction from Spallanzani, who was annoyed by the relatively unknown Prochaska’s largely justified criticism of his own position. Spallanzani’s attack on Prochaska was published under the pseudonym “A. Castiglioni”; it was shortly answered with a defense signed “Antonius Slawik,” a name that does not appear in any contemporary records or among learned men of the time. Prochaska published two other anatomical treatises soon thereafter. These, De came musculari (1778) and De structura nervorum (1779), was illustrated and contained a number of new observations. In 1780 Prochaska published a work on the abrasion of human teeth with age, which his pupil J. Pesina later used to work out a system for estimating the age of horses.

Prochaska's 1781 treatise on the generation and origin of monsters set out his views on embryology. His principal work, Commentatio de functionibus systemalis nervosi, was published in 1784.

On his return to Vienna, Prochaska published several editions of a textbook on physiology as well as some interesting work on the relation of the circulation of the blood to the nutrition of body tissues (such as the growth and simultaneous destruction of bone) and several observations on pathology. From about 1910, he attempted to interpret the phenomena of life according to the romantic tenets of Naturphilosophic.

Achievements

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  Georg Prochaska was one of the first among physiologists who wrote the first genuine textbook on physiology and created the concept of nerve conduction among other theories. He was a staunch promoter of the modern reflex theory.
  
  Prochaska was also a pioneer in the field of neurophysiology, being 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.
  
  Another Prochaska's achievement was in his study and description of the "sensorium commune" as the core mechanism of the reflex. He was able to demonstrate and prove 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, a work that was later combined with John Augustus Unzer"s The Principles of Physiology as one publication, being translated and edited by English physiologist Thomas Laycock (1812–1876).

Works

More photos

• book

  • Lehrsatze Aus Der Physiologie Des Menschen: Zum Gebrauche Seiner Vorlesungen

    (Volume 1)

    1797
  • Adnotationum Academicarum Fasciculus Tertius 1780
  • Adnotationum Academicarum Fasciculus, Continens I. Observationes Anatomicas De Decremento Dentium Corporis Humani, Quibus ... Anatomicam Monstri Humani. 1780
  • Adnotationum Academicarum Fasciculus Alter 1781
  • Abhandlungen der römisch 1787
  • de Structura Nervorum 1779
  • Disquisitio Anatomico-Physiologica Organismi Corporis Humani Ejusque Processus Vitalis: Cum Tabulis Aeneis 1812
  • De Carne Musculari Tractatus Anatomico-physiologicus... 1797
  • Bemerkungen Über Den Organismus Des Menschlichen Körpers 1810
  • Adnotationum Academicarum 1780

Views

In his views on embryology, Prochaska opposed the prevailing notion of preformation, and, based upon his own observations of monsters, argued against the ideas of Bonnet, Haller, Spallanzani, and their supporters. He chose, rather, to champion the view offered by C. F. Wolff, whereby the fetus develops progressively by differentiation from uniform tissues with the emergence of organs and parts that had not existed previously. Prochaska went on to point out that such epigenesis offered the best explanation for the development of monsters, an idea that was taken up and elaborated only forty years later.

In analyzing the function of the nervous system, Prochaska was careful to differentiate between facts and theories, endeavoring to explain the workings of the nerves on the basis of observation. He attempted to avoid philosophical considerations and to refute unfounded hypotheses, which he thought to be the main obstacle to a proper understanding of nerve functions. His formulation of reflex action, as an example of nerve activity, is of particular interest. It is based upon the notion of a nerve force (vis nervosa, an analog of Newton’s vis attractiva) and of a sensorium commune, which coordinates all impressions passing to the individual nerve centers.

The vis nervosa is divisible and can exist in even severed nerves; a portion of the nervous system can retain its activity although separated from the rest, and it may therefore be seen that the vis nervosa does not proceed from the brain. The neural force is, rather, latent in the nerves, and it remains latent until it is activated by a stimulus. The stimulus may be either internal or external, and the activity of the nerve is dependent upon its intensity. Prochaska’s vis nervosa is thus not unlike the modern notion of the nerve impulse.

Prochaska postulated the existence of two kinds of nerve fibers. One of these conducts sensory impression from the periphery of the body to the sensorium commune (which extends from the spinal cord through the medulla oblongata and crura cerebri to the thalamus, corresponding approximately to the central gray matter), from which they are reflected as motor impressions. The other conducts “reflected” impulses from the nerve centers to the muscles and other effector organs.

Reflection is thus automatic and independent of both the will and the soul; it is not subject to physical laws, and Prochaska further rejected any mechanistic explanation. Reflex movements, he believed, could be produced either consciously or unconsciously, without cerebral control, and could even occur in decapitated animals or in anencephalous monsters. He drew a clear distinction between the sensorium commune and the seats of the intellect and the will, and thereby figures in the development of the idea of brain localization. His systematic account and rational synthesis of data were influential on Marshall Hall, F. A. Longet, and Pfliiger, among others, largely between 1830 and 1860.

Quotations: "But since the brain, as well as the cerebellum, is composed of many parts, variously figured, it is possible, that nature, which never works in vain, has destined those parts to various uses, so that the various faculties of the mind seem to require different portions of the cerebrum and cerebellum for their production."

"The external impressions which are made on the sensorial nerves are very quickly transmitted along the whole length of the nerves, as far as their origin; and having arrived there, they are reflected by a certain law, and pass on to certain and corresponding motor nerves, through which, being again very quickly transmitted to muscles, they excite certain and definite motions. This part, in which, as in a centre, the sensorial nerves, as well as the motor nerves, meet and communicate, and in which the impressions made on the sensorial nerves are reflected on the motor nerves, is designated by a term, now adopted by most physiologists, the sensorium commune."

Connections

mentor:

Anton Haen

mentor:

Joseph Barth

References

• Dictionary of Scientific Biography Volume 11
  1975
• From Georg Prochaska to Jan Evangelista Purkinje
  1987