Martin finally finds himself in Max Gottlieb's bacteriology class. Gottlieb, during his lecture, shows himself to be a highly knowledgeable and intelligent man, taking from science, literature, and philosophy. Most of the students do not have a great affinity for Gottlieb, and, at most, they find him useful and admirable as is illustrated by the discussion the students have about the professor after his class. However, Martin can relateto him and to what he does in his laboratory. He imagines himself working the way Gottlieb works.
He is quite happy in Gottlieb's bacteriology class, and he begins to work late nights in the laboratory. Gottlieb sees him working late one night and invites him to join him for some sandwiches. The sandwiches seem wonderful and foreign to Martin, and he loses himself in the experiences that Gottlieb recounts to him. The two men forge a kind of friendship or a tutorial/mentor relationship. Gottlieb tells him of the times he spent in London and Stockholm, he tells him of Marseilles. He tells him also of his children and encourages Martin. Gottlieb notes that he will probably not make a good physician but, instead, a good laboratory scientist.
Completely enthralled in bacteriology, Martin becomes humbled as to the amount of knowledge he does not yet have. He shows himself to be rebellious in medical classes, to professors, and in conversations with friends and even considers dropping medicine and specializing in bacteriology.
He feels as though he has no one to speak with about this turmoil inside of him. He cannot speak to Clif, his roommate, because Clif rarely takes anything seriously, and so he finds a willing ear in Madeleine, who is always "sympathetic and sensible." Martin believes that Madeleine truly understands him and decides that he wants to marry her.
Madeleine is, however, not all together perfect. She is what Martin calls an "improver," a woman who is always trying to "improve" or change her man in the ways of vocabulary, taste, etc. Still, Madeleine, in her good moments opens up to him and, one time in particular, admits that she herself is "ordinary" despite all her appearances and her "bluffing." Martin proposes to Madeleine and even promises to become the "successful" doctor he has, until this point, adamantly criticized, in order so that they may have everything they want.
Their relationship continues to have its ups and downs, even after the proposal. Martin promises Clif that he will work as a waiter with Clif during the summer at a hotel in Canada, a promise to which Madeleine snobbishly opposes. She does not want him to be a lowly waiter. They break off their engagement twice. The last time happens right before Martin leaves with Clif for the summer. And although he has broken up with Madeleine, Martin is excited for the coming year because Gottlieb has appointed him as an undergraduate assistant.
During the summer in the Canadian hotel, Martin and Madeleine write to each other, and by mid-summer they are re-engaged.
Martin begins his own research, and his sense of observation and curiosity is encouraged, once again, by Gottlieb, with whom he works. At one point, Gottlieb asks Martin to run a laboratory errand for him and go to Zenith General Hospital to obtain a specimen. It is here that he meets a seemingly impertinent and strong-minded nurse named Leora, whom he later gets to know and begins to like.
Leora, a girl from Dakota, tells Martin about her background and herself and Martin begins to develop a serious affection for her. He proposes to her and finds himself engaged to two women at once. Not knowing how to solve his dilemma, or how to choose between them, Martin invites them both to lunch at the same time leaving them to decide for him. Madeleine is insulted and leaves him, whereas Leora stays and commits herself to him. She claims that she will not leave him despite the seeming foolishness of staying with him. She tells him, however, that he now belongs to her and cannot go around with other women. Martin finds himself very happy at the way things turned out.
In these chapters appears one of the major conflicts in the novel, which is the struggle of the physician versus the struggle of the laboratory scientist. Martin's classmates all seem to belong to the "physician" category, most of them wanting to be successful and wealthy doctors. Others simply want to help people, such as the Reverend Ira Hinkley claims. But Martin finds himself an outsider. He is not like his classmates in that he does not view success in the same light; in fact he continuously rages against it. He is, instead, a laboratory man. He loves Max Gottlieb, who is the consummate symbol of the laboratory/research side of science.
Not only does Martin admire Gottlieb, but he loves the idea of him because Martin is, after all, filled with idealistic and romantic notions of the scientist working late at night in his lab, in search of the truth. Lewis, from the beginning of the novel, is trying to illustrate and criticize the problems that exist within the medical profession, which are problems that begin to arise even while Martin is still in medical school. Competition, for instance, seems to be one factor in the problematic web of science. From the beginning even Doc Vickerson, the old country doctor, is said to have a nemesis in the form of another doctor, Dr. Needham.
In Chapter 5, Lewis begins one of his sub-sections (III) by calling Martin "in no degree a hero," yet a "seeker of truth who stumbled and slid back all his life . " Here it becomes apparent that the protagonist of this modern novel—in this epic or myth of sorts—is not the typical hero, instead he is more of a man who seeks truth but finds difficulty in the search. For example, Martin is idealistic, and he talks and talks about what he believes and, in fact, Martin does believe what he says. However, he also finds himself giving it all up in an impulsive proposal to Madeleine. He says to her that he will become that "successful surgeon" he so despises so that the reader can see that Martin Arrowsmith is not a man who is altogether incorrupt or impossible to tempt.
Perhaps the best thing that happens to Martin in these chapters is that Madeleine leaves him, and Leora accepts him. Madeleine is too much of an "improver" for Martin to find himself feeling the freedom he needs to become the kind of man he wants to become. Martin feels freer with Leora because, although he occasionally likes the luxuries of life, he is "simple" in many ways. Leora accepts him for who he is, likes Vaudeville, is not impressed by big dinners, prefers simplicity, and better complements Martin in this way.
It becomes apparent that although Martin is an independent thinker he is not capable of being alone. He falls in love frequently and easily, which coincides with his romantic nature. Although Leora is seemingly strong-minded when we are first introduced to her, she is the kind of woman that wants to make her husband happy. Lewis's portrayal of women throughout is less than flattering, sometimes submissive, and sometimes frivolous. Lewis intends to portray Leora as "the good wife," which may irk the modern reader. It is important, however, to also remember that this book takes place in the early 1900s.