Camillo Golgi's *reazione nera* — the black reaction of 1873 — let silver chromate crawl into a scattered few neurons and blacken every soma, axon and finest dendrite against transparent yellow tissue. This system reads that slide aged: the amber ground darkened by decades into deep brown, the branching cells settled to a near-black tracery. It is Cajal's "brownish black upon a transparent yellow background," rendered at the value a real specimen carries after a century in the drawer.