Suppose axon A enters a ganglion (cluster of neurons)

and axon B leaves on the other side. Shortly after an experimenter stimulates A, an impulse travels down B.

We want to know whether B is just an extension of axon A or whether A formed an excitatory synapse on some neuron in the ganglion, whose axon is axon B.

How could an experimenter determine the answer?

Try to think of more than one good method. Presume that the anatomy within the ganglion is so complex that you cannot simply observe the course of an axon through it.