We get a description of Winnemac, a fictional state in The United States, located somewhere between Michigan, Ohio, Illinois, and Indiana.
We also find out that the narrator is mostly interested in telling us about the University of Winnemac.
At twenty-one, Martin Arrowsmith is preparing to enter medical school at Winnemac U. School is his whole world by this point, and all he wants to do is live out his ambition to become a great man.
At first, his hero is a Professor named Edward Edwards, who doesn't do any research but instead smokes beside fireplaces and charms students with his interesting stories about chemistry.
While attending one of Edwards' parties, Martin becomes restless. But he gets excited when he hears Edwards talking about a professor on campus that never does anything but hang out in his laboratory.
The guy's name is Max Gottlieb and he studies bacteria day and night. What's even more amazing is that this guy apparently spends just as much time trying to disprove his own observations as he does proving them.
Martin leaves the party in the middle of the night and walks by the university's main medical building. Beneath the light outside it, he spots a slim man.
The guy glances at Martin, then turns away mumbling to himself, lost in thought. Martin can't help but feel transfixed by the guy.
On the first day of medical school, Martin is proud but nervous. He keeps thinking about performing an operation and accidentally killing someone.
Walking into the main medical building, he decides that he's going to study bacteriology with the Max Gottlieb guy who never leaves his lab.
He goes to this lab to visit Gottlieb and asks him whether he can enter his class early, since most students don't take Gottlieb until their second year. We also find out that Gottlieb is the same man Martin saw standing outside the medical building after Martin left Edwards' party, mumbling.
Gottlieb thinks that Martin is too young and ignorant to take his class, and he's not afraid to say so. Martin goes away feeling crushed, but also determined to please Gottlieb someday.
Martin begins med school and feels squeamish at having to dissect dead human bodies.
To make things worse, one of his lab partners is a guy named Ira Hinkley who spends most of his time preaching the gospel of Jesus Christ to everyone around him. Martin couldn't care less about religion.
Ira talks to Martin all the time about saving people's bodies and souls, but Martin replies that all he wants to do is make lots of money.
Martin doesn't actually believe this; he just wants Ira to leave him alone.
Along the way, he joins a fraternity and falls in with a group of other medical students named Angus Duer, Fatty Pfaff (what a name!) Clif Clawson, and of course, Ira Hinkley. Angus is a snob, Clif is a class clown, and Fatty is the butt of everyone's jokes.