Dr. Codellas received his medical degree in 1922 from the University of Minnesota School of Medicine, and did an internship at the University of Tennessee, Memphis. He came to California where he was licensed in 1923.

He had a general medical practice in San Francisco, and was Asst. in Tropical Medicine, and Lecturer in Medical History and Bibliography at UCSF. His interests in the medical history of ancient Greece led him to research and lecture on the topic; several presentations were made to meetings of the American Association for the History of Medicine, and the 11th International Congress for the History of Medicine in Zagreb, in 1938. On his return from the latter meeting, he was honored with a dinner by the Greek community of San Francisco. He surveyed the greek medical manuscript resources of the major libraries in europe, and brought home many photographic copies.