Medieval Drugs III: How Do I Drug Thee? Let Me Count the Ways.

This is my third and final post about medieval drugs. A big “thanks” to Joe Gabriel for recommending Points to me and to Trysh Travis for giving me a soapbox for sharing some of my interests and original research with the Points community!

Among the favorite stock images of modern medicine are the scientifically dosed drug, measured in identical pills or graduated syringes, and the thermometer. While both are modern inventions, the hypodermic syringe and thermometer reflect a tendency, shared by later medieval Islamic and European physicians, to quantify drugs, their qualities, and medicinal actions. The tendency to quantify drugs, common by the end of the Middle Ages, is the third stage in the process I proposed in my first post, by which herbal medicines were transformed into “drugs” by physicians, pharmacists, and patients who began to look at their medicines in new ways. That transformation took a number of forms and for a variety of reasons, which I’ve grouped under the themes of individualism, exoticism, and scholasticism in these three posts.

The accurate measurement of drugs, in terms of both their strength and quantity, is central to modern medicine, and began in the High Medieval universities.

By “scholasticism” I mean the intellctual processes of subjecting pharmaceutical remedies to the philosophy and science taught in the schools and universities, especially mathematics and Aristotelian physics. Universities were an invention of the High Middle Ages, a way of organizing the already present schoolmasters and students into corporations with more effective legal, economic, academic, and even spiritual powers. By about 1225 the cities of Paris, Oxford, Cambridge, Bologna, Padua, Salamanca, and Montpellier all had thriving universities. These universities provided the social and economic foundations for novel thinking about matter and physics in general, and about drugs in particular.

One of the most important developments in the medieval university, and one with a direct impact on modern science and medicine, was the practice of applying mathematics to non-spatial concepts, like heat or speed. Before the universities, these concepts could only be measured qualitatively (that pot is hotter, that horse is faster), and not quantitatively. Since Aristotle had considered quantity and quality different categories of definition, and not to be mixed, it took a huge mental leap for mental scholars to make the connection as step out of Aristotle’s shadow. If you want to quantify speed or heat, you need to develop the idea of velocity or temperature, respectively. This may sound downright modern and “scientific”, but medieval physicists took the idea of quantification and ran with it. Masters in Oxford, especially, tried to quantify non-spatial concepts that have no place in modern science: one tried to measure doubt on a sliding scale, another to measure the amount of charity in a man, and another even the amount of Christ in the Eucharistic host (yes, these are all real).

The “modernity” of medicine is often depicted by quantification, as in dosage, or body temperature.

These are extreme examples, but they’re indicative of a broad trend in Western society outlined by Alfred W. Crosby in his book The Measure of Reality. He identifies quantification as one of the most important changes in Europe in the period 1250-1600. He doesn’t really touch on medicine, but quantification changed that field as well. In this context, it’s hardly surprising that scholars of pharmacy would also want to measure exactly the amount of hot, cold, wet, or dry (Aristotle’s four elemental qualities) in a medicinal substance. 

One aspect of medical quantification goes back to Galen, who practiced and write extensively in the second-century Roman Empire. He advocated measuring the relative heating or cooling action of a medicinal substance according to a scale of four degrees, based on the effects observed in the patient (i.e. the first degree barely registers, the fourth might kill you). Later Islamic physicians, the heirs of Galen, fine-tuned this scale by also measuring dryness and moisture, and subdividing the degrees into beginning, middle, and end of each degree. Medieval European physicians adopted this Arabic-Galenic system in the eleventh century, and it formed the basis of scholastic pharmacy for centuries to come. The system of degrees works well if the physician prescribes only “simples,” single ingredients, but how is the physician supposed to measure the qualitative strengths of a compound medicine, a drug made up of two or more herbs, or even dozens for that matter?

Al-Kindi (801-873), Arab philosopher and physician, from Baghdad. His quantification of medical theory influenced later medieval European pharmacy.

Michael McVaugh, in several of his publications, has traced the solutions to this problem of how to quantify the actions of new, more complex drugs to masters in the universities of Montpellier and Bologna. These physician-professors, led by Arnald of Villanova (whom I mentioned in my first post), master in residence at the medical school of Montpellier between 1290 and 1300, applied more complex quantification to their pharmacology to predict the resulting final degrees of a compound medicine and to determine the final effect of varying weights of a drug. Arnald’s solutions derived from reading in Latin translation the Arabic Islamic philosophers al-Kindi (801-873) and Averroës (ibn Rushd, 1126-1198). Al-Kindi, in particular, advised a geometric progression to the four degrees, which could then be applied to the calculation of intensities in a compound medicine.

A simple drug with no discernible action was called “temperate” and calculated at a ratio of 1:1 (equally hot and cold). A drug that is hot in the first degree has a ratio of 2:1 (twice as much hot as cold), while the second, third, and fourth degrees increase exponentially (4:1, 8:1, 16:1). The same system of ratios also applied to dryness and moisture, but was not considered as important as heat. To give a simple example, if a physician compounded a drug out of two herbs, one hot in the second degree (4:1) and another cold in the first degree (1:2), then the ratios are added to determine the final quality of the drug. The sum ratio of 5:3 represents a gentle drug that can heat a patient just below the first degree (calculated at 2:1).

These are only the start of a medieval compound medicine. The pharmacist needs to measure, grind, mix with sugar (or honey, beer, or wine), and calculate its strength.

But what does a physician or pharmacist do with a more complex drug? He has to perform some relatively complex mathematics (or merely guess, which probably happened most of the time). Arnald’s contemporary and fellow medical master Bernard de Gordon offered a test case in his work of 1308 called On the Preservation of Human Life. (A translation of part of this work is found in Faith Wallis’s excellent new collection Medieval Medicine: A Reader). For a patient with excessive phlegm in his or her urine (an excessively cold and wet condition), he prescribes a drug made of 6 oz. hyssop, 4 oz. mint, 3 oz. absinth (wormwood), 2 oz. calamint, 2 oz. red roses, 1 oz. anise, 1 oz. fennel, mixed into a syrup with one pound of sugar-water or honey. (It actually sounds quite tasty, but that much absinth is worrying.) The main ingredients, hyssop, mint, and absinth, were all considered hot and dry, and according to the ground rule of medieval pharmacy—cure contraries with contraries—were used to counteract the cold and wet phlegm. I won’t repeat all of Bernard’s calculations here, but he determines that the compound drug has a heating ratio of 50:14, or hot about midway between the first and second degree. And he admits that this calculation is “rough”, since he has ignored the potential cooling aspect of the water and heat of the honey!

A university-trained physician scientifically diagnoses disease from his patient’s urine. This process will provide the indicators for correctly compounding drugs specific to his body and condition.

In reality, almost no medieval physician or pharmacist would go through these calculations, but possessing the ability to do them would be a mark of pride and constituted a form of advertising. University-trained physicians were selling a new kind of medical theory and a new kind of drug, which were part of what Roger French calls the Good Story in Medicine before Science. The moral of the Good Story was that only educated, Latinate, male physicians possessed the knowledge to accurately diagnose disease and prescribe drugs of the right quality and quantity. The discerning merchant in fourteenth-century France or Italy, daily engaged with his own forms of quantification, would probably gravitate toward a physician who also used mathematics. The new physician doesn’t simply gather some chamomile from the garden to make a soothing tea, but takes chamomile and a dozen other substances, local and exotic, then compounds, measures, analyzes, and doses them in a scholastic fashion, turning the natural herbs into philosophical drugs.