Langleys nicotine test

The Langley Nicotine test is used to determine the relay-site of autonomic fibers.

The test is the following: First stimulate the preganglionic fiber and notice the response that appears. By adding a large dose of nicotine, the ganglion (site of relay between pre- and postganglionic fibers) is blocked. Now the preganglionic fiber is restimulated again.

If there is still a response, the fiber does not relay in the ganglion. But if there is no response, the fiber relays ("synapses") in the ganglion.