Wednesday, August 28, 2013

A leech’s work for August

Even today, the work of physicians and other medical practitioners varies somewhat from month to month. In the United States, many foodborne infections peak during the summer months:

Many foodborne infections are most common during the summer, as shown by the examples of Salmonella, Campylobacter, and Vibrio in the figures above. The graphs are from CDC. Foodborne Diseases Active Surveillance Network (FoodNet): FoodNet Surveillance Report for 2010 (Final Report). Atlanta, Georgia: U.S. Department of Health and Human Services, CDC. 2011. Accessed at  on August 27, 2013.

 Many airborne allergens are also seasonal. For example, in central Texas cedar pollen is found primarily during the winter months:

Weekly totals of the daily cedar pollen counts (in grams per cubic meter) from channel KVUE in Austin, Texas. The television station takes daily pollen counts outside its studios. The data shown in this graph illustrate the period from August 5, 2012 (the start of epidemiological week 32 of2012) until August 3, 2013 (the end of epidemiological week 31 of 2013). The peak occurred during week 4 of 2013, which was from Sunday, January 20, until Saturday, January 26, 2013; this week is labeled as 13-04 on the graph above. The cedar pollen data were obtained from on August 8, 2013 and the daily counts were used to generate weekly totals, with the epidemiological weeks numbered as described at

 While modern medical practitioners can expect some variation from month to month in terms of which conditions are more common, access to medications does not generally vary much from season to season. Influenza vaccines may only be available before and during the influenza season, but otherwise most medicines can be obtained at any time of the year. However, in Anglo-Saxon times most medications were based on plants, and not all plants were available throughout the year. Different plants could be harvested during the different months of the year. Some plants could be dried for use over an extended period of time, though fresh and dried herbs may differ in effectiveness.

In the old Anglo-Saxon calendar, the lunar month roughly corresponding to August was known as Weodmonath, or the month of tares (weeds), because it is a peak time for weeds and other plants. August was apparently a peak time for harvesting medicinal herbs as well, based on evidence from the harvesting suggestions contained in the Old English Herbarium. This Old English medical text mostly consists of a translation of the Herbarium of Pseudo-Apuleius, a Latin text originally written as early as the fourth century. The Old English Herbarium survives in four Anglo-Saxon manuscripts. August was the most commonly mentioned month recommended for harvesting the medicinal herbs included in the text, being listed as the optimal month for six herbs: wood betony (Stachys officinalis), cinquefoil (Potentilla reptans), sweet flag (Acorus calamus), wall germander (Teucrium chamaedris), aster (Aster amellus), and melilot (Melilotus officinalis). I generated this list of August herbs by searching the online text of the Cockayne translation of the Old English Herbarium as well as printed versions of two more modern translations by Anne Van Arsdall (Medieval Herbal Remedies: The Old English Herbarium and Anglo-Saxon Medicine) and Stephen Pollington (Leechcraft: Early English Charms, Plant Lore, and Healing). The modern English and scientific plant names listed above are from The Old English Illustrated Pharmacopoeia by M. A. d’Aronco and M. L. Cameron. Future blog postings will explore these August herbs in more detail.

Even today August is considered a good month for collecting herbs in temperate zones. Near the beginning of the month I received a gardening newsletter by email, reminding me that this would be an optimal time to harvest many culinary and medicinal herbs for peak potency. So when you snip your herbs this month, you are taking part in a tradition going back hundreds of years. August would have been a busy month for Anglo-Saxon leeches (healers) as they collected medicinal herbs to last over the coming months.

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