Most of us today, particularly in North America, tend to regard as the only real medical doctor someone who not merely has a degree of some sort from a medical school, but who has also passed an internship at a hospital (if not a residency), in addition to passing a local medical society's entry exams and gaining some hospital admitting privileges.
We tend to think , in other words, that the only real medical doctor is a full MD in the lay sense of that technical term, who is licensed to deal directly with acutely ill patients , giving them all forms of narcotics and IV needles, can perform minor outpatient operations and is able to admit them to nearby large general hospitals.
In the British Commonwealth (outside of Canada), rather than a doctorate in medicine (M.D.) being the first medical degree, it is one reserved for medical researchers doing a PhD thesis in medicine. (DM=PhD in medicine= MD.)
One gets an initial BM/BS (BM=MB) and then goes off for various internships, residencies, local medical society and or speciality society exams, hospital admitting privileges etc just as brand new MDs do in North America.
Interestingly, none of the many people included in the Oxford team that Howard Florey assembled to develop penicillin were full MDs, in that lay sense of the word, including Florey himself.
(So Dr Florey was licensed, but only to do operations on research animals but not licensed to deal with humans in the local general hospital..... Dr Chain wasn't even licensed to give needles to research animals !)
But in 1944, his old university in Adelaide gave Florey an honorary M.D. degree and he used it for the rest of his life with pride, as he did all of his honorary degrees.... without indicating their honorary nature.
His first well-known article (on penicillin) in 1940, lists him only as having a M.B.
By 1941 with his second article on penicillin, he could and did add a FRS to that.
By 1949 he is listed ,as chief author of the two volume history called simply "Antibiotics", with a MA, MD, PhD and FRS : that old oddball MB is forgotten history.
By, contrast Henry Dawson's rival penicillin effort had a much smaller team of just four people, but both he and Dr Meyer had M.D.s ---- an important distinction in 1940s American research hospitals, where by contrast with today, the PhD was a low degree indeed.
(His other team members ? Hobby had a PhD in bacteriology and Chaffee a BSc in chemistry.)
Obscure degrees, in author listings DO matter ...
Florey's team was oriented by their training and hence personal inclination , to fundamental research on on the nature of penicillin and away from saving individual lives.
Dawson's team was dominated, by training and hence personal inclination, to saving individual lives with therapeutic penicillin .
This matter of obscure degrees after researchers' names then turns out to matter greatly ...