Conclusion

Abstract

In this chapter I highlight the book’s three main conclusions. First, Herman Boerhaave can be seen as the beginning of a new and international school of clever chemists and physicians, who named themselves the Boerhaave school. Second, in the eighteenth century the perception of the bodily fluids changed thanks to new research methods and scientific instruments, contributing to a new medicine. Finally, the redefinition of the nature of the fluids and the development of a new medical system undertaken by members of the Boerhaave school contributed to revolutionary advancements in chemistry and medicine at the turn of the nineteenth century.

The case studies on saliva, blood, urine, milk, sweat, and semen ultimately boil down to three main conclusions. They concern the impact of the Boerhaave school , the role of chemistry of the fluids for physiology and pathology, and how these preceded many aspects of modern medicine in the nineteenth century. These conclusions, I hope, reinforce further studies on medicine and natural philosophy in the eighteenth century.

The first conclusion I draw concerns the importance of the Boerhaave school in the long eighteenth century. In October 1818, for example, the immense library and art collection of the late physician and professor of medicine, Matthias van Geuns (1735–1817), was auctioned in Utrecht.¹ Among the rich collection of books, theses, and manuscripts on matters medical, chemical, botanical, theological, philosophical, and historical sat a noteworthy picture gallery of 12 portraits, mounted in gilt frames of ebony. The first five portraits were those of Hippocrates, Thomas Sydenham, Friedrich Hoffmann, Georg Ernst Stahl, and Herman Boerhaave. The final seven comprised of portraits of Johannes de Gorter, Bernhard Siegfried Albinus, Gerard van Swieten, Albrecht von Haller, Hieronymus Gaubius, Johannes Oosterdijk Schacht, and finally an engraving of a bust of Boerhaave in a black frame.² Such a collage of deceased yet very distinguished physicians and chemists memorialised the Boerhaave school. It was an international school of which Van Geuns had surely envisioned himself a part, even though he had never met its originator.

At first glance Van Geuns’s intriguing collage of portraits may appear an ode to a bygone age, but on closer inspection, it also poignantly demonstrates the importance and longevity of the medical research developed by the members of the Boerhaave school . For indeed long after Boerhaave’s death in 1738, the Leiden professor continued to inspire the works of and bonds between his disciples. When in 1775 a 70-year-old Gaubius delivered his speech in Peter’s Church to celebrate the bicentenary of the founding of Leiden University, he reflected on medical history and observed that ‘people have eventually seen the rise of the Boerhaavian school, not a new school, but one very old, based on the Hippocratic one’.³ This school of physicians, Gaubius argued, was imbued with the spirit and system of Boerhaave, grounded in indisputable discoveries and pure reasoning. Gaubius retired that same year, but he continued to work, overseeing a revised edition of his pathology textbook as well as the publication of António Sanches’s seminal study on venereal disease . In correspondence with his old-time friend Sanches, Gaubius wrote to him he was impressed by his ‘vivacity of spirit’, joking that his must be proof of the distinction between body and soul.⁴

Some 20 years earlier, Albrecht von Haller retired from the chair of medicine, yet continuing to be one of the most prolific writers. In 1753 he left the university in Göttingen and returned to his native city of Bern. But despite retreating from teaching and increasingly experiencing short-sightedness, his fluent pen never slowed. While in Switzerland he wrote philosophical novels as well as an 8-volume magnum opus, Elementa Physiologiae Corporis Humani (‘Physiological Elements of the Human Body’).⁵ The hefty volumes narrated all physiological phenomena, supported by elaborate anatomical descriptions and experimental results. Some parts in the book departed from the way Boerhaave had originally thought about them—particularly in the case of the concepts of sensibility and irritability.⁶ This was not so much a departure from Boerhaave, but a logical consequence of Boerhaave’s anti-authoritarian outlook, wanting his students to think for themselves and improve upon the knowledge previously obtained. And still, up to his late 70s, Von Haller continued to think about his former teacher, as he wrote to his daughter:

Fifty years have almost elapsed since I was the disciple of the immortal Boerhaave; but his image is continually present to my mind. I have always before my eyes the venerable simplicity of that great man, who possessed, in an eminent degree, the talent of persuading.⁷

Beyond people’s minds and letters, the image of Boerhaave and his school was advanced and promoted in the material and visual culture of the eighteenth-century society. Commissioned by Boerhaave’s daughter, Johanna Maria de Thoms (1712–1791), a monument was erected in honour of her father in Peter’s Church in Leiden in 1762 (see Fig. 8.1). Designed by Frans Hemsterhuis (1721–1790) and constructed in the workshop of master mason Antoni Wapperom (1729–1781), the Boerhaave memorial was an oval urn of white marble placed on a rectangular pedestal of black marble. The funerary vase was modestly adorned with a flame on top and six heads linked together by drapery, representing the four stages of life in men and women: childhood, youth, maturity, and old age. The six heads may also implicitly have been a symbol of the virtue of Prudentia of the present, past, and future: intelligentia, memoria, and providentia.⁸ The pedestal was decorated with Boerhaave’s profile portrait suitably set against a staff of Asclepius crossed with a burning torch. The inscription read ‘dedicated to Boerhaave’s health-bringing talents’.

Fig. 8.1

Boerhaave memorial. Engraving by Abraham Delfos, in Gerard van Swieten, Commentaria in Hermanni Boerhaave Aphorismos de cognoscendis et curandis morbis (Leiden, 1742–1772). (Credit: Rijksmuseum, Amsterdam. CC0 1.0)

The monument came to represent the continued flourishing of the Boerhaave school and medical research. For when Paulus ’s-Graeuwen (1715–1779) was appointed the new professor of medicine and chemistry at the University of Groningen in 1771, he commissioned his new house to be adorned with lavishly ornamented wallpaper depicting flowers, ribbons as well as the white marble vase of Boerhaave’s memorial statue.⁹ This was no coincidence, for as a student ’s-Graeuwen had been part of the last cohort attending Boerhaave’s lectures in Leiden in 1736 and 1737. Following a career as a medical practitioner in the city of Zutphen, ’s-Graeuwen succeeded Johannes de Gorter as the new professor of medicine and chemistry at Harderwijk in 1755.¹⁰ Thanks to the intervention of Gaubius—who played a pivotal role in the appointment of medical professors at Dutch universities, and thereby secured Boerhaave’s legacy—’s-Graeuwen was subsequently appointed to Groningen in 1770.¹¹ Once in the north, ’s-Graeuwen inherited the chemistry course by his predecessor Wouter van Doeveren and extended it from three days to four days a week.¹² In his inaugural lecture, ’s-Graeuwen explicitly aligned himself with Boerhaave, praising him for having combined the works of the ancients with those of the moderns, verifying both by his own experience and observations. And on a more personal note, ’s-Graeuwen stated that ‘I will keep in memory that I myself had been a student of his, and as I recall his most dearest admirer’.¹³ The memorial and wallpaper, in short, perfectly illustrate that the community of medical researchers following in Boerhaave’s footsteps was widespread and continued to thrive until the end of the eighteenth century. And as this book has shown, Boerhaave’s fame was continuously spread by his students, who played an important role in the transmission of his ideas long after his passing.

By keeping Boerhaave’s image alive members of the Boerhaave school also consolidated their own public image, simultaneously establishing and legitimising the central place of chemistry in medicine. Gerard van Swieten, for example, used Abraham Delfos’s engraving of the Boerhaave memorial as the frontispiece to his magnum opus, the Commentaria (see Fig. 8.1).¹⁴ This made the book in itself a monument to Boerhaave, and at the same time, it aimed to establish Van Swieten as his intellectual successor—a title which, arguably, might just as well apply to Gaubius, Von Haller, and others. Van Swieten institutionalised the Boerhaave school by completely reorganising the medical faculty in Vienna. He established a botanical garden, built a chemical laboratory, and expanded the anatomical theatre. The bases for teaching the theory and practice of medicine were, of course, Boerhaave’s textbooks: the Institutiones medicae for physiology, Van Swieten’s commentaries on Boerhaave’s Aphorismi for medical practice, Boerhaave’s Materia medica for pharmacy, and finally, Boerhaave’s Elementa chemiae for chemistry. It was not until 1785 that Pascal Joseph von Ferro (1753–1809) observed that Boerhaave’s textbooks were no longer considered the best for use in medical education.¹⁵ By analysing the works of De Gorter, Gaubius, Von Haller, Van Swieten, and many other Boerhaave disciples, this book has shown that the Boerhaave school had been a medical and a cultural phenomenon, which involved multiple generations of physicians.

The second conclusion I want to highlight concerns the central role of chemistry of the fluids played in the conceptualisation and formalisation of physiology and pathology in the eighteenth century. From the sixteenth century onwards, anatomical investigations uncovered the structure of the human body and anatomists continued to do so throughout the eighteenth century.¹⁶ But in order to better account for the functioning of the living body, an understanding of physiology was necessary. This explains the reaffirmed interest in the bodily fluids, their properties, and variability depending on certain conditions. By means of new methods and instruments, Gaubius and Thomas Schwencke were able to examine the nature of blood more thoroughly. In laboratories, heating, evaporation, distillation and fermentation, putrefaction, and crystallisation, as well as other chemical processes, made it possible to see how the fluids behaved under various circumstances. These in vitro observations of saliva, blood, and milk were then used to better understand in vivo processes of digestion, nutrition, and secretion. In short, with the help of chemistry, medical professors and students gained new understandings of physiology.

In addition to the healthy body, chemistry of the fluids assisted in explaining the causes and effects of diseases in new ways. Based on chemical analyses, the comparison of bodily fluids such as sweat and semen with morbid secretions like phlegm and inflammatory discharges was a way to gain new pathological knowledge. A concrete example of this, as I have shown, was the elaborate experimentations performed with urine, enabling new explanations for the cause of bladder stones. Johannes de Gorter, likewise, developed a chemico-pathological theory of the disease of catarrh, rooted in a neurological description of obstructed perspiration and stagnating particles turning sharp. This theory directed De Gorter’s preferred treatment, namely the prescription of the ammonia, which would induce sweating and dissolve the sharpness of the fluids. Gaubius ultimately undertook the Herculean task of describing all possible causes of disease in terms of the changeable chemical properties of the fluids. His systematic theory of disease or pathology recognised the importance of symptoms and morbid anatomy but was innovative in that it proposed a set of basic principles through which the aetiology or the causes of disease could be explained.

Although the bodily fluids as materials of study were at the forefront in this book, it is undeniable that scientific tools and instruments, their development and application, significantly accelerated advances in physiology and pathology.¹⁷ The introduction of various measuring instruments enabled physicians to probe the fluids beyond their first-hand sensory experiences. From 1718 onwards, Boerhaave, Gaubius, and Schwencke measured the temperature and weight of blood by means of thermometers and hydrometers.¹⁸ De Gorter rebuilt Santorio’s weighing chair to measure his insensible perspiration and correlated it with the humidity of the air by using Petrus Belkmeer’s design of a hygrometer. Often requiring some skill and assistance, these measuring instruments allowed for repetition and a common ground for comparison with other measurements taken. While measuring instruments were designed to passively record, others had a more modifying impact. The facilities of the chemical laboratory equipped physicians to chemically manipulate the nature and behaviour of the fluids in various conditions. Medical faculties across Europe founded chemical laboratories where professors and students, with the help of assistants, performed chemical procedures for research and educational purposes. The invention of Boerhaave’s little furnace, in particular, enabled the slow and controlled heating and distilling of bodily fluids, as well as other vegetal and animal materials, making it the ideal instrument for students to learn the practice of chemistry.¹⁹ Therapeutic devices like breast pumps appeared in the medical marketplace, too, promoting the flow of milk and other fluids. Although contemporaries debated the results produced by these instruments, their usage provided a framework for thinking about nature. Instruments and chemical practices helped produce and refine key concepts, such as chemical principles. As such, the various configurations and actions of the instruments applied to bodily fluids significantly contributed to the formation of a new medicine in the eighteenth century.

Finally, in identifying the Boerhaave school as an important community of researchers who established an eclectic medical theory based on the analysis of the bodily fluids, this book nuances some longstanding assumptions about revolutionary breakthroughs in medicine and chemistry at the turn of the nineteenth century. In recent years scholars have started to move away from the dominant focus on the chemical revolution around 1800, arguing that earlier developments in the fields of agriculture, pharmacy, and mineralogy were of crucial importance to chemistry.²⁰ This book strengthens this line of argument, and additionally details the importance of Boerhaavian chemistry in eighteenth-century medicine, arguing that it preceded and formed the basis of many of the revolutionary developments of the early nineteenth century.

The traditional perception of revolutionary changes taking place in the nineteenth century has long been the dominant view, and one to which many nineteenth-century scientists themselves contributed.²¹ For example, in a paper read at the monthly meeting of the Medical Society of Victoria in Melbourne, Thomas Shearman Ralph (1813–1891) stated: ‘Up to a recent date, it has been remarked, that the history of the life of the red corpuscle of the blood had yet to be written; to this I add, that the organic, chemical, physiological, and pathological history of the blood as a whole, has yet to be furnished to the medical student’.²² While Ralph certainly made valuable observations, medical students had been applying microscopes and chemical experiments to the analysis of blood for more than a century at that stage. But it is on the basis of such observations that scholars have previously characterised the chemistry of the early eighteenth century as a discipline suffering from theoretical stagnation and fallaciousness, and this theory was supposed to be proven by the misguided acceptance of the existence of phlogiston as an element. It was only from the nineteenth century onwards, they have argued that scientists came to realise the value of chemical methods to medical practice and diagnosis. Animal chemistry or clinical chemistry, as it was called, explored physiological processes as chemical reactions, and it was predominantly executed by chemists who were not physicians.²³

But having traced blood, urine, and other bodily fluids in the laboratory, this book has emphasised the wide-spread recognition among eighteenth-century medical men—physicians, professors, and students alike—of chemistry as a pillar of medicine.²⁴ The Boerhaave school established and disseminated theoretical innovation in physiology and pathology by means of innovative scientific instruments and chemical experiments. As time progressed, the level of abstraction and quantification improved thanks to the investigation of larger research samples and the application of more accurate measurements. Researchers isolated the elementary substances and chemical properties of bodily fluids, and they made their findings relevant to public health concerns. In other words, the Boerhaave school established chemistry as an academic discipline with an influence beyond the confines of the chemical laboratory, from the early eighteenth century onwards. Doing so, members of the Boerhaave school anticipated many aspects of modern medicine at the turn of the nineteenth century.

By analysing Boerhaave as the beginning of a new and international research programme, this book opens up new avenues for research on medicine and natural philosophy in this period. Boerhaave’s students may be traced in other fields of expertise, most notably in botany and natural history, as is the case for Martinus Houttuyn (1720–1798) and Johannes le Francq van Berkhey (1729–1812).²⁵ Also, the role of chemistry for the appreciation of mineral waters or the study of tropical diseases in the Americas and Asia may be re-evaluated by taking the Boerhaavians into account.²⁶ If we consider Boerhaave’s death in 1738 not the end of an era, but rather a new beginning, the study of erudite individuals and academic institutions, of chemical practices and the production of medical knowledge in the Dutch Republic and far beyond may gather new momentum.