This evolution follows through the entire novel. Things become, almost unnoticeably, more and more grave. Robert Merril says, "Heller has in fact divided Catch-22 into three parts."" The first sixteen chapters are full of comedy, humor and simple absurdities. Almost all of the events taking place, such as the tragedy of the soldier in white, or the carefree promoting of officers, are presented lightheartedly. Even those events that are gruesome or depressing such as Snowden's death have a slight comic characteristic to them. As the book progresses however, the comedy and theme swap places, bringing the theme to the front while sending the comedy to a hiding place. The soldier in white for example, shows more horror of reality the second time it is shown than the first. The entire second portion of the novel takes on a more serious tone, but still keeps its comedic element prevalent as well. The most obvious contrast between the sections of the book comes between the first and third sections. Theme seems to have even more pervasiveness in the third portion than did the humor in the first. Yossarian's harsh reality is finally brought to terms. The death of Snowden is again remembered and repeated and still is more gruesome than the last. Even the soldier in white makes yet another appearance and still has more tragic characteristics to his troubles. Yossarian realizes that most everyone he has come to know in the Air Corps has died (either literally or on paper), and that he soon would do the same unless he took charge of his situation. Yossarian's thoughts and actions, in a way, mirror the evolvement of the novel itself. .
"As things get worse for him [Yossarian], the jokes come less rapidly and eventually trickle to a halt. This plunge from exhilaratingly happy to depressingly serious is made all the more pronounced by Heller - (Pennarum).
As stated, Yossarian enjoys his position less and less, possibly because as the novel progresses, Yossarian has fewer "enjoyable- people to interact with or relate to.