Around 30 of Liddel’s books are concerned with the identification of plants and herbs, and their use in the manufacture of medicines. Liddel not only taught medicine but was a practising physician himself. Liddel became physician to the Court of Brunswick and treated the Duke and his family, and on his return to Scotland he carried on practising medicine.
At Wolfenbüttel, Liddel had access to one of the finest Renaissance gardens in Europe which was renowned for its collection of herbs.
Liddel owned pocket herbals, designed for use in the field. One, by the French botanist Antoine du Pinet, is heavily annotated in Liddel’s hand with additional information on the curative properties of plants and recipes. Liddel was at least the third owner of this particular book which he purchased in 1596, the year in which he gained his medical degree from Helmstedt.