Jonas Edward Salk (; October 28, 1914 - June 23, 1995) was an American medical researcher and virologist. He discovered and developed one of the first successful polio vaccines. Born in New York City, he attended New York University School of Medicine, later choosing to do medical research instead of becoming a practicing physician. In 1939, after earning his medical degree, Salk began an internship as a physician scientist at Mount Sinai Hospital.

After City College, Salk enrolled in New York University to study medicine. According to Oshinsky, NYU based its modest reputation on famous alumni, such as Walter Reed, who helped conquer yellow fever. Tuition was "comparatively low, better still, it did not discriminate against Jews, ... while most of the surrounding medical schools--Cornell, Columbia, University of Pennsylvania, and Yale--had rigid quotas in place." Yale, for example, accepted 76 applicants, in 1935, out of a pool of 501. Although 200 of the applicants were Jewish, only five got in. During his years at New York University Medical School, Salk worked as a laboratory technician during the school year and as a camp counselor in the summer.  During Salk's medical studies, he stood out from his peers, according to Bookchin, "not just because of his continued academic prowess--he was Alpha Omega Alpha, the Phi Beta Kappa Society of medical education--but because he had decided he did not want to practice medicine." Instead, he became absorbed in research, even taking a year off to study biochemistry. He later focused more of his studies on bacteriology which had replaced medicine as his primary interest. He said his desire was to help humankind in general rather than single patients. "It was the laboratory work, in particular, that gave new direction to his life."  According to Salk: "My intention was to go to medical school, and then become a medical scientist. I did not intend to practice medicine, although in medical school, and in my internship, I did all the things that were necessary to qualify me in that regard. I had opportunities along the way to drop the idea of medicine and go into science. At one point at the end of my first year of medical school, I received an opportunity to spend a year in research and teaching in biochemistry, which I did. And at the end of that year, I was told that I could, if I wished, switch and get a Ph.D. in biochemistry, but my preference was to stay with medicine. And, I believe that this is all linked to my original ambition, or desire, which was to be of some help to humankind, so to speak, in a larger sense than just on a one-to-one basis."  Concerning his last year of medical school Salk says: "I had an opportunity to spend time in elective periods in my last year in medical school, in a laboratory that was involved in studies on influenza. The influenza virus had just been discovered about a few years before that. And, I saw the opportunity at that time to test the question as to whether we could destroy the virus infectivity and still immunize. And so, by carefully designed experiments, we found it was possible to do so." Answer this question using a quote from the following article:

What did he study?
medicine.