Fig. 1: Ramón y Cajal’s drawing of nerve impulses corresponding to the olfactory and visual systems.
From: Scientific illustrations of SARS-CoV-2 in the media: An imagedemic on screens

Note the arrows that indicate the neuronal flow in a scientific illustration that introduces dynamic polarization, a hypothesis for functional analysis of the brain that remains relevant today. This figure is not covered by the Creative Commons Attribution 4.0 International License. Reproduced with permission of Juan A. De Carlos; copyright © Cajal Institute (Centro Superior de Investigaciones Científicas, CSIC), all rights reserved.