So students would sometimes stay until they got bored, then drop out and start practicing anyway

From Increasingly Competitive College Admissions: Much More Than You Wanted to Know by Scott Alexander.

Nowadays college is competitive partly because people expect it to be their ticket to a good job. But in the 19th century, there was little financial benefit to a college degree.

Suppose you wanted to become a doctor. Most medical schools accepted students straight out of secondary school, without a college degree. In fact, most medical schools accepted all “applicants”, the same as Harvard. Like Harvard, there was sometimes a test to make sure you knew Greek and Latin (the important things for doctors!) but after that, you were in.

(This article has some great stories about colonial and antebellum US medical education. Anyone who wanted could open up a medical school; profit-motive incentivized them to accept everybody. Medical-schooling was so profitable that the bottleneck became patients; since there were no regulations requiring medical students to see patients, less scrupulous schools tended to skip this part. Dissection was a big part of the curriculum, but there were no refrigerators, so fresh corpses became a hot commodity. Grave robbing was a real problem, sparking small-scale wars between medical schools and their local towns. “In at least 2 instances, the locals actually raided the school to obtain a body. In 1 case, the school building was destroyed by fire, and in another, 2 people, a student and a professor, were killed.” There were no requirements for how long medical schools should last, so some were as short as nine months. But there were also no requirements for who could call themselves a doctors, so students would sometimes stay until they got bored, then drop out and start practicing anyway. Tuition was about $100 per year, plus cost of living and various hidden fees; by my estimates that’s about half as much (as percent of an average doctor’s salary) as medical school tuition today. This situation continued until the Gilded Age, when medical schools started professionalizing themselves a little more.)

In doing genealogical research, it has been quite striking to read about the post-Civil War careers of the former plantation owning families. I have read in enough detail perhaps a dozen career arcs for former plantation owners and their adult sons. Suddenly, that whole institution was economically unviable and gone. In the space of five years, they all became publishers, manufacturers, doctors, lawyers and the like. We now separate those into two categories - Professions (doctors and lawyers) and Businessmen (manufacturers and publishers) and we treat them differently. Back then, they were undifferentiated. If you could successfully do it, you did it. No credentials required.

In one particularly striking instance, the younger son, Preston, goes off to war. At the battle of Vicksburg, he is struck by a Minié ball. The bullet entered his lower right jaw and exited the upper left cheek, a horrific wound.

There on the battle field was likely the start of his new career. He dressed his wound by threading a silk handkerchief through from bullet entry to exit, staunching the bleeding during the battle.

With the fall of Vicksburg, he is paroled and invalided back home. Within five years he is a practicing doctor. I find no record of attending school for medical training or anything of the sort. My suspicion is that he had a year of recovery which involved some pretty crude restructuring of his jaw and wound. Given that he lived in a remote agricultural area, his treatment was almost certainly self-treatment. My further guess is that with his familiarity from treating his own wounds, he probably started working on other returning wounded soldiers through the end of the war.

And all of a sudden he is a practicing doctor.