I think this is a formal distinction in the UK, but in Australia I think both groups can be called Dr.
They can be called Dr, but will respond with a snippy "Mr Smith" if you do it.
Can you elaborate on this? Until germ theory and lesion theory, western medicine lacked the concept of etiology of disease, limiting the ability to accurately and consistently diagnose disease. Doctors operated within a Galenic framework and relied heavily, if not exclusively, on uroscopy for diagnosis (hence diabetes mellitus -- to pass through sweet urine).
> surgery was the only field of medicine that actually worked
"War is the only proper school for surgeons." -- Hippocrates
Doctors, following Hippocratic and Galenic traditions, would refuse to perform surgery, due to its usage of knives and causing harm to the patient. Even the study of anatomy by means of human dissection was discouraged until the 16th century, when Vesalius and others published their landmark works. Prior anatomical publications (such as those by Leonardo da Vinci) likely presented dissections of other animals as if they were human, due to the presence of structures such as the rete mirabile.
In the absence of antibiotics, surgery was a risky, and frequently lethal procedure. One surgery famously led to the death of 3 people. Before the advent of chloroform in the 1800s, there was no way for surgeons to effectively anesthetize subjects. Consequently, surgery was not looked upon favorably, nor considered a reliable medical practice.
I found The Devil's Doctor by Philip Ball to be an interesting book on this sort of thing.