Treatment to Syphallis

While discussing in class about the Tuskegee experiment, I was always wondering if there was a treatment that could help all of the people affected. I know that they book talked about Penicillin being the magic medicine that was discovered to cure Syphilis. Why would the doctors not use it on some people to see the results? Wasn't that they main idea of the experiment? Were patients elsewhere, who were probably white, being treated with Penicillin? This made me think about how much useful information was being withheld from the patients that was hurting their chances at recovery. I realize that the idea of the experiment was not to cure the infected, but it seems like in that time period they were be more concerned about advancing medicine than repressing people.