The British Library manuscript Harley 585 is significant for containing two distinct collections of medical material. It begins with a copy of the Old English Pharmacopeia; this collection is then followed immediately by a second, independent collection of cures in Old English. The second text is the only extant copy of the medical collection known to scholars today as the Lacnunga. ‘Lacnunga’ is the Old English word for ‘remedies’, a title given to the collection by Cockayne, who first edited the text in the 1860s. The manuscript contains no formal illustrations, even in the Old English Pharmacopeia which in other manuscripts is sometimes illustrated. Ker dates the majority of the manuscript to the end of the tenth or beginning of the eleventh century, with the table of contents to the Herbarium and the final part of the Lacnunga as perhaps slightly later; this agrees with the chiefly late Old English linguistic features of the text (even if these features are somewhat mixed).

A date in the late tenth or early eleventh century would position the compilation of the Lacnunga as later than Bald's Leechbook, and perhaps not too distant in time from the translation of the Herbarium Complex. However, the Lacnunga has frequently been treated as somewhat different in character from these other collections. It lacks the sophisticated system of organisation observed in Bald's Leechbook and is the only extant collection to not have a table of contents. It is also the smallest manuscript, measuring only 192 x 115 mm, which may indicate that it was meant to be a portable aid. However, the collection has mostly attracted attention for its ‘magical’ or ‘superstitious’ content, which is generally considered to be popular in its origin.

In his influential book on Anglo-Saxon medicine, Cameron describes the Lacnunga as ‘folk medicine at its lowest level’. He contrasts this collection with Bald's Leechbook and Leechbook III, arguing that together these repre sent ‘examples of the two sides of the Anglo-Saxon medical world, the learned against the popular’. Although not all scholars would defend such a binary division, the general idea that the Lacnunga is more representative of popular or folk practice is widespread.