Galen's spirit system. Historical artwork of the internal organs depicting Galen's concepts of anatomy and spirit. Galen introduced the spirit system, consisting of natural spirit in the liver, vital spirit in the heart and animal spirit in the nervous system. Claudius Galen (129-199) was a physician who worked in ancient Rome. He began by studying the anatomy of dead gladiators, and later studied animals when human dissection was forbidden. He made many important discoveries about the movement of blood in the body, but mistakenly believed that the heart was a single, rather than a double, pump.