Hippocampus (1890–1891)

Cajal said, “As long as our brain is a mystery, the universe, the reflection of the human consciousness, will also be a mystery.”

llustration of Cajal's Hippocampus scientific drawing by Dawn Hunter, 11" x 14," marker and pen on paper.

Hippocampus (1890–1891), Cajal inferred the flow of information between neurons from their structure and relative position. His ‘Law of Dynamic Polarization’ posits that each neuron is polarized: it has dendrites, through which signals are received, and an axon through which signals are transmitted to the dendrites of the next cells in the pathway. Thus, simply by observing the morphology and location of neurons in a tissue, he was able to discern the direction of signal transmission within the hippocampus.