Johannes Peter Müller (14 July 1801 – 28 April 1858) was a German physiologist, comparative anatomist, ichthyologist, and herpetologist, known not only for his discoveries but also for his ability to synthesize knowledge.

He was the son of a poor shoemaker, and was about to be apprenticed to a saddler when his talents attracted the attention of his teacher, and he prepared himself to become a Roman Catholic Priest.

There, under the influence of G. W. F. Hegel and Karl Rudolphi, he was induced to reject all systems of physiology which were not founded upon a strict observation of nature.

[6] Müller made contributions in numerous domains of physiology, in particular increasing understanding of the voice, speech and hearing, as well as the chemical and physical properties of lymph, chyle and blood.

His first important works, Zur vergleichenden Physiologie des Gesichtssinns (On the comparative physiology of sight, Leipzig, 1826) and Über die phantastischen Gesichtserscheinungen (On visual hallucination, Coblenz, 1826), are of a subjective philosophical tendency.

The first work concerns the most important facts as to human and animal sight, the second sounds depths of difficult psychological problems.

Müller gave order to these facts, developed general principles and showed physiologists how recent discoveries in physics and chemistry could be applied to their work.

In it, for the first time, the results of human and comparative anatomy, as well as of chemistry and other departments of physical science, and tools like the microscope, were brought to bear on the investigation of physiological problems.

[8] Thus light, pressure, or mechanical stimulation acting on the retina and optic nerve invariably produces luminous impressions.