Santorio on the Six Non-Naturals
A Small Book of Great Significance
A small book in octavo, arranged in a sequence of aphorisms, can reveal more about the transformation of early modern medicine than many complex treatises. The book in question, Santorio’s celebrated Ars de statica medicina (Venice, 1614), transformed the Galenic ideal of equilibrium between qualities and humours into a balance of fluids and solids that could be measured on a scale. Measuring this equilibrium is considered an ‘art’ (ars) that consists of drawing diagnostic conclusions from the imbalance in a person’s weight, and from the alteration of parameters such as the pulse or the temperature. As the body has the capacity to cyclically restore its healthy conditions — a process today known as homeostasis — sudden alterations of this process might help the physician to foresee the development of a pathological condition, thereby preventing the onset of it.
Santorio Santori (ed.), Commentaria, in artem medicinalem Galeni. Libri tres (Lyon, 1632), title page.
Appearing in Venice at the beginning of the seventeenth century, the work and its methodology strike us as surprisingly modern. After all, this is the age of Galileo (1564–1642), Bacon (1561–1626), and Descartes (1596–1650), the alleged champions of what was known as ‘the Scientific Revolution’. And yet the author of this book, the Italian physician Santorio Santori (1561–1636), known also in Latin as Sanctorius of Padua, makes no claim of revolution. In fact, the book closely follows the Galenic doctrine of the ‘six non-naturals’ (sex res non naturales), those factors which physicians had to monitor to prevent disease or to restore the patient’s health.
The ‘six non-naturals’ in the Galenic tradition were 1. air (aer), 2. food and drink (cibus et potus), 3. exercise and rest (motus et quies), 4. sleep and wakefulness (somnus et vigilia), (5) ingestion and excretion (inanitio et repletio), and 6. mental affections (animi affectus). They were regulated by doctors on the basis of the patient’s constitution, and therefore varied from individual to individual.
The codification of the series of the six non-naturals was handed down by Galen, whose Ars medica (also known as Articella or Microtechni) provided the standard diagnostics rationale of medical semiotics from the Classical to the Early Modern period. In it, Galen explained not only the importance of monitoring the six non-naturals but also how to recognise diseases via a complex of signs (semiotics) that the physician had to constantly monitor in a patient. Changes in the colour of the skin, qualitative composition of the organs or the tissues, and alterations in shape or size, all pinpointed ongoing conditions that could be addressed by regulating regimen (food and drink), changing the environment (air) and the psychological disposition (mental affections), or by modifying daily habits of sleep and exercise. A complex of practices that the Greeks called δίαιτα or ‘way of life’ and that we know today more prosaically and reductively as diet.
Diagnostic Challenges: The Problem of Latency and the Weakness of Traditional Approaches to Prognosis and Diagnosis
However, these signs all appeared after a period of latency, called neutrality (neutrum), which was almost impossible to diagnose, representing the transition from the healthy (sanitas) to the ill status (morbus). The literature on diagnostic methods blossomed throughout the Middle Ages and the Renaissance, adopting complex logical procedures to decide which signs were associated with which disease and how to recognise the transition from the state of health to that of neutrality. The names of Martin Akakia (1497–1551), Francisco Valles (1524–92), Girolamo Capivacci (1523–89) and, above all, Prospero Alpini (1553–1617), are amongst the most prominent in this tradition, with the latter’s work De praesagienda vita et morte aegrotantium (1601) representing the benchmark of diagnostic method up to the early eighteenth century.
One inherent weakness of this approach was that it focused on diagnosis rather than prognosis, so that the ushering of unstable health into a full-blown illness was rarely diagnosed and could not be prevented. Alpini’s title makes this case compelling, clarifying that the matter of real prognosis could only be applied to the extreme cases of life or death. But what about in between? And how could a doctor foresee the presence of a latent disease?
Santorio’s Solution: Redefining Equilibrium
Santorio Santori, De statica medicina aphorismorum sectiones septem: cum commentario Martini Lister (Leiden, 1703), frontispiece and title page.
These and others were the questions that Santorio asked himself early in his career, starting with his books on method (1603) and, above all, in his large commentary on Galen’s Ars medica (Image 1). However, it was only in the little treatise Medicina statica that he offered his solution to the puzzle. Written in aphorisms, the work is meant to be memorable in the sense of being easily memorised by doctors, which is one of the reasons why it was translated into many languages and became a true bestseller of medical literature (as we can see in Worth’s early eighteenth-century editions).
In essence, Medicina statica re-contextualised the use and purpose of the six non-naturals by transforming the very concept of equilibrium that underpinned them. In line with Galen, Santorio noticed that the body gets rid of excrements not only by faeces and urine but, most importantly, by dispersing a volatile matter called ‘insensible perspiration’ (perspiratio insensibilis) from the pores of the skin and the respiratory tract, which helps the body to cyclically return to the same weight.
Santorio posits this observation as the foundation of his experiments on equilibrium and reasons that, in a healthy individual, all other conditions remaining unchanged, the quantity of insensible perspiration can only be altered by the onset of morbid conditions. This alteration is measurable by weight, the slightest changes of which can therefore be used to detect and counteract the early roots of a disease. All that was needed was to put a man on a scale hanging from the ceiling and measure daily fluctuations of weight in healthy conditions, so that those occurring in abnormal conditions could be easily noticed by difference. Even today, Santorio’s fame in the history of medicine and science rests on the image of a man sitting on a steelyard chair (sella Sanctorii), with a mobile table in front of him (as can be seen in the above image).
In terms of diagnostics, the work represented a dramatic change from previous approaches, marking the true beginning of evidence-based medicine, where medical diagnosis is mediated by the instrument and the data it can provide about the state of the body. Along with William Harvey (1578–1657), Santorio was heralded as a pioneer of scientific medicine, and Medicina statica became a sort of manifesto of experimental medicine, especially in Britain and Ireland.
Limitations and Legacy: Santorio’s Continuing Influence
Pierre Noguez, Sanctorii Sanctorii, De statica medicina aphorismorum sectionibus septem distinctorum explanatio physico-medica: cui statica medicina, tum Gallica Cl. Dodart, tum Britannica Cl. Keill notis aucta, simul cum appendice de variolarum insitione, accedit. Auctore P. Noguez (Paris, 1725), i, p. 124.
On the other hand, Santorio could not offer new cures to his patients, who therefore continued with the standard treatments. Indeed, the little work is built around the six non-naturals, so that physicians could easily understand how to modify their approach to the patient in various contexts. Each section of the work, seven in all, with the first teaching how to measure the fluctuations of the body associated with the quantity of insensible perspiration, deals with one of the six non-naturals. They can now be linked to specific changes in body weight and, Santorio alleges, used not only to preserve the patient’s health but even to prolong his life.
The programme was ambitious, and Santorio invented other instruments that could help to rationalise diagnosis by quantifying the variance of the latency period. Many of these are still used in today’s medicine, like the thermometer and the pulsimeter. Others, like the hygrometer, are now used to measure the humidity of the environment. Santorio, however, thought that the environment could influence perspiration and health, and so his instruments achieved both results, measuring the variations in the body’s response to external stimuli.
Conclusion: The Interplay of Old and New in Medical Progress
True milestones in the history of medicine, works like those of Santorio and Harvey, are a powerful reminder that, in medicine, progress is rarely achieved by means of revolutionary processes and is more often the result of a vital compromise between the old and the new, where the new changes the meaning of what was before, granting its survival in a different form.
Text: Dr Fabrizio Bigotti, Centre for the Study of Medicine and the Body in the Renaissance (CSMBR), Pisa.
Sources
Barry, Jonathan, and Fabrizio Bigotti (eds), Santorio Santori and the Emergence of Quantified Medicine, 1614–1790: Corpuscularianism, Technology and Experimentation (Cham, 2022).