Complex sentence: While at Clark, Mall used the Born wax-plate method to create the first model of a human embryo in the United States, discovered the vasomotor nerves of the portal vein, and founded an embryological research program at the university.
Split into simpler sentences: While at Clark, Mall used the Born wax-plate method to create the first model of a human embryo in the United States. Furthermore, Mall discovered the vasomotor nerves of the portal vein and founded an embryological research program at the university.