The fourth chapter opens with a detailed textual comparison, including statistical analysis of lexicography, between Keats’ medical notes and those kept by his fellow-student Joshua Waddington. These prove that the two sets of notes derived from the same source and reveal that although Keats has essentially the same information as Waddington, his habits of concision, reorganization and cross-referencing mean that they are presented in a different – indeed, distinctive – form. The chapter finds that some characteristic features of Keats’ mature poetry are prefigured in his medical notes: striking imagery, verbal rhythms and verbal compression are all typical of Keats’ medical thought. Close readings of some of Keats’ most accomplished poems, including ‘Ode to a Nightingale’ and Hyperion, reveal the medical underpinning for much of his greatest poetry, in content, vocabulary, and style.