Retina (1887-1888)
Retina (1887–1888), the vertebrate retina originates as an extension of the brain, and light signals pass through its complex network before traveling to the brain via the optic nerve, carried by the axons of ganglion cells. This distinct pathway, beginning with photoreceptors and extending through ganglion cells, played a crucial role in shaping Cajal’s groundbreaking ‘dynamic polarization’ theory.
Through meticulous examination of retinal sections across different animal species, Santiago Ramón y Cajal discovered that the structural organization of the retina is strikingly consistent among vertebrates. He identified the presence of rod and cone photoreceptors, along with bipolar cells, horizontal cells, amacrine cells, and ganglion cells, arranged in a similar pattern across species.