Nature's Pharmacy: The Discovery of Medicinal Plants

We begin with Giovanbattista della Porta, a highly educated Italian nobleman from the mid-sixteenth century. Della Porta was an important figure in the beginnings of the Renaissance. He founded the first scientific society – the Academia Secretorum Naturae – and made important advances in philosophy, literature and science. In his pursuit of knowledge, he, like Galileo, was a leading thinker of his day. Also like Galileo, his scientific curiosity brought him to the attention of the Church and the Inquisition, a problem that plagued him repeatedly over the course of his career. Phytognomica, one of della Porta’s botanical works, is a paradoxical mix of his more modern thinking but also combined with his continued adherence to aspects of medieval folklore, including, for example, the “doctrine of signatures.”

The “doctrine of signatures” refers to the idea that the physical appearance of a plant is a sign – a “signature” – of its utility in treating human ailments. Toothwort, for example, was believed to be effective in treating
toothache. In this illustration, della Porta highlights the physical similarities between the pomegrante and human teeth, which he also compares with a pine cone. Under the
doctrine of signatures, all of these plants were thought to be valuable in treating tooth-related problems.

While the medicinal uses of toothwort are embedded in northern European herbal traditions, the uses of opium - derived from the opium poppy - have a long history that begins in western Asia, the Middle East and the eastern Mediterranean. The beneficial effects of opium-based or opium-like drugs, such as morphine, have been enormous, but unfortunately so have the negative and narcotic impacts – from the opium wars of the early nineteenth century to the contemporary opioid crisis.

Dating from 1682, this image is the cover of Opiologia by the German physician Georg Wolfgang Wedel, a massive treatise on the opium poppy. Wedel was an iatrochemist, an early form of pharmacology that sought to understand how chemical compounds impacted human behavior. Wedel’s research, and the massive volume he published, corresponded with the increasing presence of opium in European medical treatments. Wedel noted its potential for providing beneficial treatments, but also its lethal characteristics. He says, “Opium is a life-anchor for him who uses it properly and with circumspection, but in the hands of the unskilled it is a semblance of Charon’s boat, and pernicious as a sword in the hands of a madman.”

Dodoens’ work published in Latin was influential throughout Europe and became a key reference for information about the uses of plants of all kinds. But only about 60 years after its publication, the English botanist John Gerard completed a new English translation, sometimes using almost identical illustrations. Gerard used Dodoens’ work as his starting point, but also included information synthesized from other well-known botanists such as Mattioli, Bock, L’Obel and Fuchs. Gerard’s eventual publication of the work as his own was controversial, but the impact of his new herbal was profound and quickly became a significant addition to botanical knowledge of his day.

In his herbal, Gerard describes a variety of uses for “hempe”, including one seemingly no longer in use, saying, “the feed given to the hens causeth them to lay eggs more plentifully.”

We end with the foxglove, a plant forever associated with the late eighteenth century English physician William Withering. The use of foxglove in medicinal treatments began well before William Withering – Elizabeth Blackwell had recorded the plant as an emetic over four decades earlier, and it had been used in folk treatments for centuries before that. But Withering’s work, An Account of the Foxglove, and Some of Its Medical Uses, was the first comprehensive and thorough examination of the plant as it related to medicine.

Specifically, Withering examined the utility of extracts from foxglove leaves to treat dropsy, another term for edema, the bodily swelling that often precedes heart failure. Its emetic properties, when used in the right amounts, could be life-saving. But Withering’s careful analysis also notes that at very high doses foxglove extract can also be fatal. The kind of carefully reasoned and systematic examination of a plant’s medical uses seen in William Withering’s work marks the beginning of the transition from an archaic understanding of plants to the many discoveries of plant-based drugs that have characterized modern science, which we examine in more detail in – The People and Plants Shaping Modern Medicine.