[1] Leydig studied philosophy in Munich from 1840, and medicine at the University of Würzburg from 1842 under Martin Münz (1785–1848), August Schenk, and Franz von Rinecker (1811–1883).

[1] He received his doctorate in medicine at Würzburg on 27 August 1847, becoming an assistant in the physiology department, while also teaching histology and developmental anatomy under Albert von Kölliker (1817–1905).

[1] Leydig paid further tribute to other contemporary anatomists, particularly Johannes Peter Müller (1801–1858) for his work on glands and emphasizing cellular doctrine for pathology.

Franz von Leydig's work on neural tissue influenced Norwegian zoologist and polar explorer Fridtjof Nansen (1861–1931), who along with Wilhelm His, Sr. (1831–1904) and Auguste-Henri Forel (1848–1931), were the first to establish the anatomical entity of the nerve cell.

These special cells are present in small numbers where they follow the course of the blood vessels, but increase in mass considerably when surrounding seminiferous tubules.

[1] In addition to its historical importance, Leydig’s "Lehrbuch" is significant for his description of a large secretory cell, found in the epidermis of fishes and larvae amphibians.

[1] Leydig is also known for describing large vesicular cells that occur in the connective tissue and the walls of blood vessels in crustaceans in 1883: four different types of the latter have been determined.