When and how did Hahnemann college become a standard medical school?

Cecil’s column today: What’s the difference between an osteopath and an MD? - The Straight Dope reminded me of the question posed above. By the time I finished college in 1959, Hahnemann was just one of the five medical schools in Philly. But it started out as purely osteopathic in the 19th century. I once spent some time trying to track this down, but the information was rather sketchy. Somehow between 1900 and 1950 it changed, but when, and more interestingly how (osteopaths hiring standard MDs to teach) was never explained. Hence my question.