Serendipity, not the movie starring John Cusack and Kate Beckinsale, is defined as "the faculty of making fortunate discoveries by accident." Science describes beneficial scientific accidents as "the Principle of Limited Sloppiness." It is a fact that the vast majority of the most important scientific discoveries were made by accident, especially medical discoveries.
Countless lives have been saved by the accidental discovery made by Luigi Galvani in 1786. While experimenting with frog legs, which he had strung on a copper wire, he discovered that if the legs touched a metal rail, it would close an electrical circuit and would reanimate the muscles in the frog legs. Although this may have inspired Mary Shelley to write Frankenstein: or, The Modern Prometheus about a reanimated corpse, it was more importantly used as the basis for the theory behind the defibrillator, which is used extensively to reanimate people's hearts that have stopped beating.
Another accidental discovery by Dr. Sydney Ringer is used to prolong a heartbeat in a patient. Actually it was his lab technician that made the discovery, but Dr. Ringer is credited with the discovery of the Ringer's solution commonly used in hospitals to resuscitate patients who are suffering from traumatic injuries.
The epitome of a sloppy lab technician, Alexander Fleming, left a culture dish containing staphylococcus bacteria out while he went on vacation. Upon his return he discovered that a mold had invaded and was destroying the infectious bacteria. This mold became one of the most important medicines that mankind has in its arsenal against infections and infectious diseases, penicillin.
Although the discovery of electricity predates Benjamin Franklin, he is credited for his experimentation with the phenomena and his discovery of its properties. From Franklin's planned experiments, an accidental discovery that has been most beneficial to modern medicine was made by Wilhelm Roentgen in 1895. During Roentgen's experiment with electrical discharges, Roentgen's hand came between a screen and the tube where electrical discharges were occurring. He observed that he could see through the skin of his hand and literally see the bones in his hand. This discovery was the basis of the invention of the X-ray machine.
More recently, neurosurgeon Professor Andres Lozano was experimenting with electrodes planted in the brain of an overweight patient, trying to suppress the patient's appetite. While stimulating his brain, it was discovered that he had almost total recall of events that had happened decades earlier. This accidental discovery of stimulating the brain from within with electricity is hoped to become a treatment for Parkinson's disease, depression and Alzheimer's disease in the future.
There is no doubt that these accidental discoveries are some of the most important scientific discoveries made by man. It is hoped that fortuitous accidents will continue to benefit our species and we will continue to hear scientists exclaim, "Eureka!"