Here’s lookin’ at you, squid Scientists first learned about the electrical properties of neurons by studying squid (Hodgkin & Katz, 1949). Why squid? The axons that send signals to the wall of their body, or mantle, are exceptionally large—so large that scientists could insert electrodes directly into them. Electrical recordings revealed fluctuations in the electrical potential in the axon that, as scientists realized, could only have been caused by electrically charged particles flowing in and out of the cell.