Complex sentence: In the early days of electrical research a common method of detecting electric current was by means of a frog's leg galvanoscope for which a good supply of live frogs was kept to hand by the researcher ready to have their legs prepared for the galvanoscope.
Split into simpler sentences: In the early days of electrical research, a common method of detecting electric current was by means of a frog's leg galvanoscope. A good supply of live frogs was kept to hand by the researcher ready to have their legs prepared for the galvanoscope.