He developed Bergmann's rule (that populations and species of animals of larger size are found in colder environments).

[1] He microscopically examined the cells of the retina to determine which of them convert light into neural signals that lead ultimately to visual perception: the cones and the rods.

After graduating from high school in Holzminden in 1832, he studied medicine and natural sciences at the universities in Göttingen and Würzburg.

[6] This regular connection between heat balance and body size in animals was named after him - Bergmann's rule.

[4] Bergmann died in Geneva on 30 April 1865, following his return from Menton, where he had resided for the winter because of his deteriorating health.

[2]: 249 Later in the same year Heinrich Müller arrived at the same conclusion from careful measurement of moving shadows of the retinal blood vessels, using the principal of motion parallax.