Synaptic transmission of nervous impulses through the last abdominal ganglion of the cockroach

In a previous communication (1936) we have described the response of the cereal nerve of the cricket when the cercus is subjected to acoustic stimuli. In the course of that work we attempted to trace the afferent fibres to their destination by recording from the ventral nerve cord at various levels anterior to the last abdominal ganglion. It was immediately apparent that, while some of the fibres from the acoustically sensitive end-organs of the cercus ran directly through the ganglion and up the cord, others terminated in the ganglion in synaptic relation with a relatively small number of fibres running forwards in the cord and yielding action potentials of considerable magnitude. Contrary to expectation we found that, subject to certain conditions noted below, the random activity in the abdominal nerve cord was never large enough to obscure the wanted signals, and it seemed to us that the preparation offered an excellent opportunity for an examination of the properties of a central nervous synapse. This paper describes the results of this examination.