For two thousand years the state-run libraries of imperial China systematically assembled standard collection of books from the past and present.  Although the collections themselves were lost through warfare and fire, the classified catalogues prepared by the Privy Director of Books   were often used in compiling national bibliographies for the state-sponsored dynastic histories. Through these and other catalogues we learn much about books can be sampled through quotations in medieval encyclopaedias. These lectures discuss the dynamic of loss and survival; the role of the imperial state in manipulation book culture through classification and selective preservation; the significance of lost books as an index of superseded knowledge and values. An analysis of two specific cases demonstrates the insights to be gained through textual reconstruction, and inadequacies of standard classification in times past and present.  Medical Chinese literature emerges as a richer, more problematic, less docile body of work than the orthodoxies of the last millennium would wish.