“You've Got to Work on This Axon”: J. Z. Young and Squid Giant Axon Preparations in 20th-Century Neurobiology**

Employing and extending Hans-Jörg Rheinberger's analytical concept of epistemic things, this essay proposes one reason why squid giant axons, unusually large invertebrate nerve fibers, had such great impacts on twentieth-century neurobiology. The 1930s characterizations of these axons by John Zachary Young reshaped prevailing assumptions about nerve cells as epistemic things, I argue. Specifically, Young's preparations of these axons, which consisted of fibers attached to laboratory technologies, highlighted similarities between giant axons and more familiar ones via lines of comparative study common to aquatic biology. Young's work convinced other biologists that the squid giant fibers were, in fact, axons, despite their unusual fused (syncytial) structures, thereby promoting further studies, such as intracellular measurements, made possible by the fiber's size. Tracing direct relations between preparations of squid axons and broader interpretations of neurons as epistemic things, this paper renders an actors’ category, “preparations,” into an analytical one. In turn, it offers glimpses into how aquatic organisms shaped twentieth-century neurobiology and how local experiments can drive broader, disciplinary changes.