Career
He was a native of Mainz, Rhineland-Palatinate. Gerlach was a pioneer of histological staining and anatomical micrography. In 1858 Gerlach introduced carmine mixed with gelatin as an histological stain.
Along with Camillo Golgi, he was a major proponent of the reticular theory that the brain"s nervous system consisted of processes of contiguous cells fused to create a massive meshed network.
Gerlach summed up his theory by stating:
The reticular theory predominated until the 1890s when Ramon y Cajal brought forth his neuron doctrine of synaptic junctions, which in essence replaced the reticular theory. Gerlach was one of the first physicians to use photomicrography for medical research.
In 1863 he published a handbook titled Die Photographie als Hilfsmittel mikroskopischer Forschung (English "Photography as a tool in microscopic science") in which he discusses the practical and technological aspects of microscopic photography. The eponymous "Gerlach"s valve" (valvula processus vermiformis) is named after him.
This anatomical structure is a fold of membrane sometimes found at the opening of the vermiform appendix.
In his article Ueber das Hautathmen (English "On skin respiration") he was the first to show that human skin uses oxygen from ambient air.