Complex sentence: He started working at a chemist in Paris where he was able to save a person intoxicated with arsenic, he decided to study chemistry and started first at the laboratory of Edmond Frémy later at that of Pierre Paul Dehérain.
Split into simpler sentences: He started working at a chemist in Paris where he was able to save a person intoxicated with arsenic. He decided to study chemistry and started first at the laboratory of Edmond Frémy and later at that of Pierre Paul Dehérain.