Final answer:
Claudius Galen ignored the teaching of Hippocrates that diseases had natural causes from within patients or their environments, instead focusing on the balance of the four elements in the body.
Step-by-step explanation:
One of the teachings of Hippocrates that Claudius Galen ignored was the idea that diseases had natural causes from within patients or their environments. Galen, a Greek physician living under Roman rule, developed his own medical theory that explained human health in terms of the balance of the four elements (earth, air, fire, and water) in the body, known as the four "humors." This theory persisted until the modern era. So, while Hippocrates focused on natural causes of disease, Galen focused on the balance of the four elements.