Before the advent of CAT Scans and MRI -- and often even with them -- a neurologist would perform a lengthy physical examination in order to tell what part of the nervous system was involved, 'localizing the lesion'. Of course, most conditions were -- and still are -- untreatable. A famous neurologist in the fifties once described his job as "Diagnose, adios."
Two neurologists are hot air ballooning when clouds come up and they realize they're lost. They go lower, and suddenly the clouds part and they see that they're passing over a field where a man is on a tractor.
One of the neurologists leans out and yells, "Hey! Where are we?"
The man on the tractor looks up and shouts back, "In a balloon!"
Then the clouds swallow them up again. The first neurologist smiles. "This has been a great day! We saw good scenery, we put back some brewskies, and now to make the day complete, the first guy we meet is a neurologist too."
"Wait a minute!" interjects his friend. "That looked like a farmer to me. What makes you say he's a neurologist?"
"Well, think about how he answered our question. He gave us precise localization and it didn't help a bit."