I found this story on @HistoryWeird's blog here. The original source was Dr. Walter J. Hoffman's Folk Medicine of the Pennsylvania Germans, 1889.
"Walter James Hoffman (1846-99) was a Pennsylvanian physician, ethnologist and author. . . . In 1889 Dr Hoffman presented the American Philosophical Society with the conclusions of his research on Pennsylvanian folklore. This volume detailed a wide array of homespun medical treatments, some valid, some based on superstitions and wacky theories. One ‘cure’ still widely practised in rural areas was for a dog bite:
“'To cure a bite, use a hair of the dog that caused it. It is sometimes placed between two slices of buttered bread and eaten as a sandwich.'
"Mumps could be cured by rubbing the swellings against a hog trough. Rheumatism could be kept at bay by carrying around a potato in one’s pocket. Excessive saliva and dribbling in children could be stopped by 'passing a live fish through the child’s mouth'. Whooping cough could be treated with daily drinks of tea made from a hornet’s nest. No less bizarre was a treatment for jaundice:
“'Hollow out a carrot, fill it with the patient’s urine and hang it, by means of a string, in the fireplace. As the urine is evaporated and the carrot becomes shrivelled, the disease will leave the patient.'"