'Soup' vs. 'sparks': Alexander Forbes and the synaptic transmission controversy.

During the twentieth century, a controversy raged over the role of electrical forces and chemical substances in synaptic transmission. Although the story of the 'main' participants is well documented, the story of 'lesser' known participants is seldom told. For example, Alexander Forbes, who was a prominent member of the axonologists, played an active role in the controversy and yet is seldom mentioned in standard accounts of the controversy. During the 1930s, Forbes incorporated chemical substances into his theory of synaptic transmission, advocating a complementarity model for the role of electrical forces and chemical substances. By focusing on Forbes and the axonologists, the controversy is simply more than a debate over 'soup' vs. 'sparks' but also involves the relative roles of electrical forces and chemical substances in synaptic transmission. The implications of this case study for the nature of scientific controversies are also discussed.