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Johann August Unzer was a 18th century doctor whose work with the central nervous system, reflexes and the consciousness impacted modern physiological studies. He was born on April 27, 1727 in Halle Germany.

Johann August Unzer

Life

He came from a family of medical practitioners. His brother Johann Christoph Unzer was a physician of royalty, and his father was also a notable physician. At the early age of twelve, he was already pursuing his medical degree at the University of Halle, his hometown university. In his years at the university, he started exploring ideas such as emotion, already exploring his ideas regarding the central nervous system. . Unzer found a companion in a professor at the school named Georg Ernst Stahl. While still attending university, he defended Stahl’s views on animism by publishing one of his first works called “Thoughts on the Influence of the Soul on its Body” . In 1748 at the age of twenty one, he received his MD. In 1749, he went on to complete his dissertation entitled “De Nexu Metaphysices cum Medicina generatim” and continued to work into the next year. After he graduated and completed his dissertational work, he went on to practice medicine in Hamburg, Germany while still developing his theories. Around this time, he connected with the Hamburg Magazine, frequently publishing on neuro-metaphysical matters. He continued to do this, and in 1759, he published his own medical journal called “The Physican” . In the following years, he published several books and articles ranging from zoology, “The Principles of Physiology”, to afferent and efferent nerves, all of which shall be looked into further.

Work

Zoology

As time went on, and while he remained interested in the fundamentals of life, he turned from a Stahlian animism perspective to a physiological perspective on animal and human life. Unzer continued his scientific work by contributing to the progress of zoology, a field that focused on all aspects of the animal kingdom, by publishing a book called Erste Gründe, which was later renamed The Principles of Physiology of the Proper Animal Nature of the Animal Organism. He focused on comparing nerves and their relationship with motions, in animals. He did this by classifying three types of motions: those of which are conscious and voluntary, those that are conscious but not voluntary and finally those that are unconscious and involuntary. He concluded that animals are like living machines, and through observation made his case that the brain contained the soul. “ He proceeded from the notion of the animal as a machine to state that some animals (beseelte Tiere) have a soul that (unbeseelte Tiere) have neither soul nor brain, and are instead moved by animal “forces”.” His ideas later came to be known as physiological metaphysics. From this point, he went on to discover a great deal about reflexes.

Reflexes

Unzer’s main contribution to the concept of reflexes was the introduction of afferent and efferent reflexes. At its most basic level, afferent reflexes are those that move inward from something external, making its way to the central nervous system. Efferent then is the opposite, where the central nervous system triggers a reflex in the muscles. Unzer himself he explains afferent reflexs: “To the end that an impression is felt…the external impression will have no other reflex action in the animal machines than that which is capable in virtue of its purely animal force, which it reflects upon the motor nerves…”. He also goes on to explain efferent reflexes: “If, on the other hand, the external impression be also felt, then the mind, according to its psychological laws, connects volitionally with it many other conceptions, the internal impressions of which can produce through the motor nerves such sentient actions as the unfelt external impression could not have developed at all, or, at least, not in combination with the will of the animal. An example of the afferent reflex would be the traditional Patellar Reflex, which is also called the knee jerk reflex. An example of the efferent reflex may be the sucking reflex babies have at birth. He used these ideas of reflexes to validate his point that animals without developed brains have some but very little ability to move: “It is for this reason, that we find animals without brain and without any traces of the mind, to be capable of very few kinds of movements” . Continuing with this idea, he delved into the possible links between consciousness and its relationship with nervous processes reflexes.

Guillotine and Consciousness

One of the major contributions that Unzer made was his study of consciousness. There was the question of whether or not consciousness was a product of all neural activity, or only higher functioning. After the first person was beheaded by Joseph Ignace Guillotin’s contraption named after him, there was a curiosity about whether there was any form of consciousness after the head was severed from the body, and was it painless. People started to wonder if beheading actually did fully kill the person, because the body of a criminal would sometimes convulse for some time after the person was “killed”. Unzer was one of the first to address this problem. From what he knew about animals and their reaction to beheading, he concluded that the same phenomena could be applied to human beings as well. He reasoned that if a signal had nowhere to go (ie once it reached the place where the head was severed), it may travel back through an efferent pathway, causing the motion that the person would have performed if he or she were whole. However, such actions are still reflexes, and do not require conscious activity, as he believed the brain was required to produce a conscious experience. Therefore, he concluded that if there was no conscious experience due to the neural impulse never reaching a brain, that there was no pain as well.

Major Works

• De sternutatione
• Gedancken vom Einfluß der Seele in ihren Körper
• Philosophische Betrachtung des menschlichen Körpers überhaupt
• Erste Gründe einer Physiologie der eigentlichen thierischen Natur thierischer Körper
• Physiologische Untersuchungen auf Veranlassung der Göttingischen, Frankfurter, Leipziger und Hallischen Recensionen seiner Physiologie der thierischen Natur
• Medizinisches Handbuch
• Einleitung zur allgemeinen Pathologie der ansteckenden Krankheiten
• D. Johann August Unzers medicinisches Handbuch vom neuen ausgearbeitet
• The Principals of Physiology

Death

He died on April 2, 1799 in Altona, Germany.

References