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By Marieke Hendriksen[caption id="attachment_3845" align="alignright" width="244"] Herman Boerhaave, J. Chapman, 1798. Source credit: http://ihm.nlm.nih.gov/images/B29694 via Wikimedia Commons.[/caption]My current research project focuses on how Herman Boerhaave's (1668-1738) medical and chemical ideas, particularly those on metals, influenced the theories and practices of his students and other followers. The longer I work on this topic, the more I notice Boerhaave's general influence on his contemporaries and the next generations. Already during his lifetime, Boerhaave was famous far beyond the borders of the Netherlands, even though he hardly left Leiden and the furthest journey he made during his life was to Harderwijk, a Dutch town about 100km from Leiden, where he gained his doctorate. A popular (alhough never documented) story told that a letter sent from China, addressed simply to 'the illustrious prof. Boerhaave, physician in Europe,' reached him without delay.Then there was Boerhaave's stove, a small wooden box-like incubator Boerhaave described in one of his text books and which students, apothecaries and amateurs constructed at least till the early nineteenth century to conduct chemical experiments, prepare ingredients for drugs, and even hatch eggs. Another trace of Boerhaave's influence on Dutch eighteenth-century culture was the continuing description of dark candy sugar as 'Boerhaave's sugar,' because he prescribed it as an ingredient in cough syrups. Yet most clearly of all can his influence be seen in both professional and private eighteenth-century manuscript recipe books.[caption id="attachment_3795" align="alignleft" width="300"] Brown candy sugar, also known as 'Boerhaave's sugar' in the eighteenth century. Image credit: © Alice Wiegand / CC-BY-SA-3.0 via Wikimedia Commons.[/caption]Although it may seem obvious that Boerhaave's medicine influenced that of other medical men, it is interesting to see how diverse his influence was. Lately I compared a number of eighteenth-century Dutch manuscript recipe books and was pleasantly surprised by the different ways in which Boerhaave's medicine influenced both medical men and others. In an anonymous recipe book that was probably compiled by a medical man of some sort, four recipes are attributed to Boerhaave, and three to his direct successor at Leiden University, Jerome Gaub (1705-1780). That this book was most likely used by a medical professional can be told from the fact that most of the recipes were written down in Latin, and measurements were given in apothecary shorthand, i.e. weights were indicated in drams.[1] Moreover, recipes for analgesics and purges to be used in persistent illnesses such as venereal disease and epilepsy, often accompanied by a note that they are only to be used if all else fails, are dominant, and ingredients like mercury, antimony, and sulphur are frequently listed.This forms a stark contrast with household recipe books from the same period, like the anonymous 'Medicamentboek' that contains recipes attributed to 'Bourhavi' [sic] against fever and coughing. The most remarkable difference with the first recipe book is that almost all recipes are in Dutch, and contain primarily readily available ingredients, such as beer, bread, wine, honey, candy sugar, herbs, spices, rhubarb, tongue of veal, red cabbage, liquorice, and vinegar. Moreover, instead of cures for persistent and grave illnesses such as advanced venereal disease, this recipe book lists cures for more common ailments such as dandruff, irritated gums, coughing and winter hands.  Although some recipes in this book have been written in apothecary shorthand, in Latin, or contain more exotic ingredients such as red coral and boiled puppies, these entries are all in a different hand than the bulk of the recipes, suggesting the recipe collector occasionally asked a medical professional to add a recipe to his or her household medical recipes book.[2]Rather than reading all these attributions to Boerhaave as direct evidence of medical networks, which is problematic, as they do not prove that the compiler had any affiliation with the names source, they can be read as proof of the diverse yet widely dispersed influence of Boerhaave's medicine in eighteenth-century Dutch society.[3] For medical men, he was a professional example whose recipes, especially the more complicated ones that contained potentially dangerous ingredients such as metals, were collected as a resource for extreme cases. For laymen, Boerhaave's name and simpler recipes, based on more readily available ingredients and aimed at more common ailments, carried equal authority.[1] Anonymous. “Receptenboekje”, ca. 1750. Museum Boerhaave Library, Leiden: BOERH a 313.[2] “Medicament boek : met een recept van Boerhaave tegen koorts”, 17XX. Museum Boerhaave Library, Leiden: BOERH a 308.[3] For more on interpreting early modern recipe books, see Michelle DiMeo and Sara Pennell, eds. Reading and Writing Recipe Books 1550-1800. Manchester and New York: Manchester University Press, 2013.