Martin notices that one of his carefully nurtured laboratory cultures has "committed suicide." He becomes vastly curious as to the cause. He is sure that the culture has staph in it. All one night he makes tests and at seven in the morning calls the hospital for more pus from the same carbuncle. Finding that the carbuncle is now healed, he can obtain no more of the same material. He rushes home to tell Leora of his discovery, only to find her gone in search of him. Visions of having arrived after years of stumbling flit through his brain.
For a week he hardly eats or sleeps, so intense is his concentration on his experiment. Gottlieb is critical, as usual, but makes some suggestions that help Martin confirm his findings of the X Principle. The reaction of close application and loss of sleep is too much for the young physician, however, and he drifts toward neurasthenia. He becomes extremely nervous, noises annoy him, and he is the victim of fears and delusions. Four days spent tramping through the Vermont hills build up enough reserve energy to support him for a while after he goes back to his experiment.
Lewis' own fears and phobias are thought to be reflected in this chapter, for example the fears connected with a railway journey. Martin still finds a balance wheel in the mature Gottlieb, who asks just the right questions and uses just the right psychology to keep his younger colleague on the right track. Leora is, as always, a sanctuary for her overwrought husband. The big break in Martin's career is now in the offing.