Sanctorius Revisited

Abstract

This chapter reflects on the epistemic processes that made the use of quantification and measurements in medicine conceivable to Sanctorius, and which might explain how these methods made sense to him in ways that they had not before. To this end, I bring into focus the relation between the categories of innovation and tradition as well as the interplay of the realms of theory and practice in Sanctorius’s works, unifying the main results of my study. Then, based on my analysis of the measuring instruments in Chap. 7, I reflect on what quantifying health meant to Sanctorius. Finally, I briefly sketch out how his measuring instruments were received. Building upon the historical analyses of the previous chapters, I present a new and revised view of the Venetian physician Sanctorius, which hopefully will contribute not only to a better understanding of his work, but also, more generally, of how knowledge was transformed in the early modern period.

In his first publication, Methodi vitandorum errorum, Sanctorius argued that there were forces, or virtues which were not related to the four primary qualities of hot, cold, wet, and dry. In doing so, he referred to the example of the “moving force of the clock” (potentia motrix horologij) which was, according to him, “the most apparent example of all” (Sanctorius 1603: 160r).¹ He explained:

No one of sane mind would say that the force of the clock relates to the temperament [temperatura], but rather to the number, position, and figure of the wheels, disks, and springs [spirae chalibea]; its inability to move, however, relates to damage to these. … What prevents us from saying that, using the metaphor of the clock, the moving force [of the body] is not a very simple substance? But that [instead] the force relates to the number, position, and figure of the bodily substance and that in these [bodily substances] is the prime mover [primum mobile], which moves the others like the spring does.² Aristotle discovered the prime matter through an analogy of artifacts; why can we not, in imitating him, in so much simplicity of judgment, philosophize about the hidden forces through the same analogy? (Sanctorius 1603: 160r)³

In arguing against Jean Fernel’s concept of occult forces which acted on the total substance of the body and could not be attributed to complexion, but were celestial in origin, Sanctorius put forward his own explanation of these hidden, or occult forces.⁴ According to him, they were the result of the number, position and figure of the bodily substances, similar to the mechanical parts of a clock. From this citation it is easy to understand how the picture of Sanctorius as the founder of a new medical science based on measurement and quantification evolved. Strikingly, Sanctorius allowed here that some physical effects could be traced back, not to bodily complexions, but to mechanical properties such as movement. In line with his critical attitude toward astrology, he refused the idea of occult, celestial causes. Moreover, in this connection, he used the famous clock metaphor that René Descartes (1596–1650) was to use some 40 years later to defend his mechanistic understanding of the body—the most prominent figure among those who promulgated a machine-like explanation of bodily operations (Siraisi 1987: 280–5; Bertoloni Meli 2016: 91–3).⁵

In the following, I take Sanctorius’s use of the clock metaphor as a key example, encapsulating the major findings of my study and demonstrating in what way the prevalent view of Sanctorius as the innovative genius needs to be revised.⁶

In fact, there are several passages in Sanctorius’s works in which he put forward the metaphor of the clock. In the Commentary on Galen, he compared the generation of the animal spirits with the movements of the parts of a clock. In doing so, he hoped to illustrate that during the production of the animal spirits, many physiological “movements” occurred at the same time, just as in a clock. Accordingly, the drawing of inhaled air from the lungs to the heart happened, for example, simultaneously to the inhalation of air by the brain through the olfactory tracts (Sect. 3.2.6). In a later discussion of the same work, Sanctorius stated that he used to compare people who trust in physicians with no anatomical experience with people who, when their clock stops working, consult a person who has never seen the inner structure of a clock (Sanctorius 1612a: 267, 738 f.). As mentioned earlier (Sect. 3.3.1), in the De statica medicina, Sanctorius compared the course of the plague in the body with the movement of a clock (Sanctorius 1634: 17v–18r). Similar to the first passage in the Commentary on Galen, Sanctorius made use of the clock metaphor in the Commentary on Avicenna, when trying to explain that the functioning of the body as a whole depended on the satisfactory interaction of many individually functioning parts. The human body resembled a clock, so Sanctorius, in which, if one wheel malfunctioned, the whole clock stopped (Sanctorius 1625: 91).⁷

Hence, these statements seem to imply that Sanctorius had a mechanistic conception of the body, picturing the latter as a machine, in which mechanical processes guaranteed its proper functioning, i.e., good health. In order to understand the human body, he held it necessary to take it apart in anatomical dissections and to observe its inner mechanisms, just as was required for the repair of a machine. Above all, Sanctorius did not refer to any machine, but to the clock, which later became the emblem of the mechanical philosophy of the seventeenth century (Van Lunteren 2016: 767).

Yet, in the preceding chapters I have shown that things are rarely as they seem at first glance. Sanctorius’s strong adherence to traditional Galenic medicine has been identified and his innovative, quantitative approach to physiology has been demonstrated to be deeply influenced by the medical tradition, too. In view of this, it does not come much as a surprise that, considered in their broader contexts, Sanctorius’s uses of the clock metaphor appear in a different light: Rather than being expressions of a revolutionary, mechanistic conception of the body as a machine, breaking with traditional concepts, Sanctorius presented them as additions or refinements of the ideas of Aristotle and Galen. In the quoted citation from the Methodi vitandorum errorum, for example, he explicitly mentioned that he used the analogy of the clock in an Aristotelian spirit. Most probably, Sanctorius had here the artifact-analogies in mind that Aristotle frequently used in describing the workings of living entities, especially regarding discussions of form and matter. Without examining these analogies and Sanctorius’s understanding of them, it is important to note that, in using the clock metaphor, Sanctorius saw himself following the tradition rather than making new departures (Grmek 1990: 116; Koslicki 1997: 77).

In the Commentary on Galen, Sanctorius referred to the clock when explaining Galenic physiological theory, the generation of the spirits, which ultimately served him to demonstrate that the movement of the brain did not result from the arteries, but from the substance of the brain, as “Galen had taught us” (Sanctorius 1612a: 267).⁸ Furthermore, after having emphasized the importance of anatomical knowledge for the physician, which he compared with the knowledge of the inner mechanisms of a clock that one needed in order to repair it, Sanctorius immediately pointed to Galen’s statement that “internal diseases can by no means be understood without the cutting of bodies, philosophy, and dialectics” (Sanctorius 1612a: 739).⁹ In the Commentary on Avicenna, he presented the picture of the body as a machine directly after the conclusion of a quaestio in which he had insisted on the qualitative and complexional nature of disease. He simply added his new analogy, without disturbing the underlying base—a process which was, however, very much in line with contemporary commentary tradition on Avicenna’s Canon, as Nancy Siraisi has shown (Sanctorius 1625: 85–92; Siraisi 1987: 351).

Thus, Sanctorius certainly did not equate the body with a machine. According to him, certain physiological processes could be measured and quantified, but the human body could not be disassembled, let alone reconstructed. It was not a machine, but a humoral body whose functions could be sometimes explained and illustrated by mechanical explanations—in some respects it was similar to a machine, but by no means identical with it. As he himself pointed out, even traditional authorities like Aristotle used analogies of artifacts to explain and understand the physical world. The technical developments of his day allowed him to widen the metaphorical field of the ancients and to include with the mechanical clock, a highly innovative instrument of the time, movements and, more generally, complex operations like physiological processes, in the comparison of artifacts and bodies. In doing so, challenging traditional medical theory was not his aim (Farina 1975: 373; Mazzolini 1994: 126).

Sanctorius’s use of the clock metaphor impressively illustrates the complex relation between the realms of tradition and innovation in his works, as encountered throughout this study; and it suggests that simply dividing early modern thinking and practice into these two categories is ambiguous and potentially misleading. Similarly, it points to the intricate interplay between the categories of theory and practice, given that Sanctorius brought an innovative technical instrument, the mechanical clock, into the sphere of theoretical medical explanations, mainly within the framework of large scholarly commentaries that were the result of his teaching of medical theory. As this indicates, the intellectual and the material are entangled with the old and the new, too, adding to the complexities of this constellation that includes, of course, also social dimensions (Valleriani 2017b: vii).

The aim of this study was to investigate this constellation—comprising innovative and traditional, practical and theoretical aspects, as well as their social dimensions—and its dynamic in all its complexities with regard to Sanctorius’s undertakings, in order to understand how he developed his innovative ideas and more generally, how innovation occurred within a highly traditional framework in the early modern period. Thus, instead of concentrating solely on the parts of his work that are, or appear to be innovative, and instead of searching for breaks and disruptions, I searched for continuities that position Sanctorius’s undertakings between traditional natural philosophical and medical concepts and the transformation, in his day, of views on nature. My interest lay in the epistemic processes which made the use of quantification and measurements in medicine conceivable to Sanctorius and which might explain how these methods made sense to him in ways that they had not before.

In the early modern period, the clock became not only a mechanical paradigm, but was also used by scholars to express the complexity of their era. The diffusion of the printed book, the journeys of exploration, and the intensifying process of urbanization are only a few of the many developments that characterized this period and contributed to change and incremental transformation encompassing economic, social, political and cultural spheres (Valleriani 2017a: 12–8). Thus, the complexity sensed by early modern scholars in a way mirrors the complexity of the processes by which new knowledge was generated in their era. It was against these complexities and from a broad perspective that Sanctorius’s undertakings were considered in this study. Thereby his role, not as a revolutionist, but as an exceptional and creative physician became manifest. This review of Sanctorius in the light of his era hopefully contributes to our understanding of processes of knowledge transformation in the early modern period. It is the major goal of this book.

8.1 Tradition and Innovation: Continuities, Reinterpretation, and Reorganization

The starting point for my investigation of Sanctorius’s role in the comprehensive process of the transformation of knowledge that ultimately led to the abandonment of Galenic medicine and to the introduction of a new medical science, based on the use of quantification and measurement in medical research, was to identify, on the one hand, the knowledge that Sanctorius changed and, on the other hand, those parts of Sanctorius’s knowledge which triggered the change. In doing so, I was able to show that Sanctorius did not develop his innovative approach to physiology despite his adherence to the medical tradition, Galenic medicine, but rather exactly because of this tradition, since he developed his methods of quantification and measurement from the core of this “knowledge system” without calling its authority into question.¹⁰ Accordingly, Sanctorius’s most famous work, the De statica medicina, was based on an ancient concept originating in Galen’s works and a principal idea of Galenism—the doctrine of the six non-natural things. Moreover, his concept of perspiratio insensibilis and also the fundamental principle on which his weighing procedures were based, namely that health is an ideal balance between ingestion and excretion, were profoundly shaped by the teachings of Hippocrates and Galen, as Sanctorius himself explicitly highlighted. His novel interpretation of the six non-natural things according to their effect on insensible perspiration becomes comprehensible when considering that, in Galenic dietetics, bodily evacuations were closely connected to the processes of digestion and respiration, i.e., to air, food, and drinks, and were influenced by the motion or rest of the body—all of them traditional non-natural factors. The fact that the traditional list of the six non-naturals included “evacuation and repletion” as a non-natural thing itself makes Sanctorius’s step appear even more plausible. In light of this, it is no longer surprising that Sanctorius chose this of all concepts to structure the results of his weighing procedures. Indeed, my experiences with the reconstruction of the Sanctorian chair have revealed the problems that Sanctorius must have faced in trying to include all of the six non-natural factors into his measurements. Therefore, it is easy to imagine that it was this traditional dietetic context that gave him the idea of examining perspiratio insensibilis in the first place. To go even further, from the perspective of Galenic dietetics, according to which balance and moderation were crucial factors in order to maintain health, the step from the idea of balance to the use of an actual balance seems, at least in retrospect, quite natural. Hence, a closer look at the intellectual context in which Sanctorius developed his novel approach to physiology revealed, firstly, that he drew on existing medical-dietetic traditions and secondly, highlighted the importance of these for his static medicine. It thus refuted the established narrative of the lone genius who developed his novel ideas almost out of the blue.

Through an analysis of the content of the De statica medicina, this study has disclosed the way in which Sanctorius developed his new medical idea, the quantification of insensible perspiration, out of a well-established Galenic doctrine. Generally, he followed traditional concepts regarding the influence of the non-natural factors on the body, but reinterpreted them by focusing on their impact on body weight and on the excretion of insensible perspiration. Interestingly, in some instances Sanctorius apparently struggled to integrate his novel quantitative findings into traditional medical theory. So, he discovered, for example, that a high amount of insensible perspiration was expelled during sleep. But according to the Galenic teachings, the third stage of the digestive process, during which bodies perspired insensibly, occurred during waking hours (Sect. 3.3.3). From today’s perspective, Sanctorius’s solution to this problem seems somewhat inconsistent and suggests that the merging of the new and the old, the compromise between innovation and tradition, was sometimes challenging for him. This is further confirmed by the fact that Sanctorius was ready, at times, not only to reinterpret, but even to revise traditional knowledge on the basis of the knowledge which he gained through his weighing procedures, as when it came, for example, to the amount of food that should be ingested for each meal (Sect. 3.3.2).

However, my analysis of Sanctorius’s stance on anatomy clearly illustrated that the revision of traditional knowledge was possible for Sanctorius only up to a point: He endorsed recent anatomical findings only as long as they could be accommodated within Galenic theory. The new material, which he integrated into his works, either had to fit within a Galenic framework, or it was refused. In doing so, Sanctorius was in line what historians have found to be the attitude generally prevailing among Medieval and Renaissance learned physicians and anatomists, such as Vesalius or André du Laurens (Wear 1981: 233–7). Galenic medicine was still conceived as providing a reliable framework in which novel elements had to be integrated.

But within this framework, as I was able to show, there was an increasing trend to quantification, ranging from Galen’s works to those of other Renaissance scholars. In this connection, it is remarkable that Sanctorius put himself explicitly in the tradition of the ancient authorities of Hippocrates and Galen, while remaining silent on, or refuting altogether, any influence of contemporary scholars on his novel approach—despite the sometimes, striking similarities between their undertakings. Of course, his recourse to the ancients has to be seen in the context of Medical Humanism, a movement that, to put it most simply, was established at the Italian medical universities in the early sixteenth century, and according to which medical theory and practice had reached unparalleled heights among the ancient Greeks, especially through the work of Hippocrates and Galen (Bylebyl 1979: 339).¹¹ To allude directly to these authorities was thus desirable. But in addition to this, Sanctorius probably worried that reference to more recent works would diminish his originality. When confronted with Obizzi’s accusation of plagiarism regarding the work De staticis experimentis, published by Cusanus in the fifteenth century, all he had to say was that the Cardinal had not dealt with insensible perspiration. For Sanctorius, this was proof enough to show that he did not take a word from him. Hence, Sanctorius neither denied his knowledge of the work nor explained in detail how his De statica medicina differed from the work of Cusanus, except for the focus on insensible perspiration. Yet, as my analysis has revealed, Cusanus had already conceptualized many of the quantitative measurements which Sanctorius later claimed to have realized (Sect. 5.3.2). This and the fact that he published them in a work with a title so similar to Sanctorius’s De statica medicina—De staticis experimentis—provides strong evidence that this is more than just a “genial coincidence” and that by ignoring the similarities Sanctorius hoped to assert his originality.

Against this background, it is, in my opinion, most certain that Sanctorius’s innovative approach to physiology was inspired by the different forms of quantification that were developed incrementally within the medical tradition. Sanctorius’s quantification efforts, however singular, were, thus, informed by a tradition of thought. Accordingly, he presented his use of measuring instruments in medicine not as a break, but as a direct advancement of Galenic medicine. By measuring different physiological parameters, he declared to have found an answer to a problem which Galen had been unable to solve: to quantify the latitude of health. In doing so, he claimed he was able to bring to medicine, which he identified as an art, a new precision which would approximate, if not achieve, certainty. On the epistemic level, Sanctorius departed here markedly from a tradition according to which certainty was exclusively reserved for scientia. And yet, he did not dismiss the Aristotelian definitions of ars and scientia. Similar to the way in which he adopted new findings of contemporary anatomists, in his own attempt to ascertain Galenic medicine, he did not abandon the fundamental principles upon which the whole discipline of medicine rested. What is more, Sanctorius appears to have been in doubt regarding the degree of certainty that his instruments and measurements could actually provide, since he repeatedly qualified his statements concerning the possibility of gaining a true and certain knowledge of quantity in medicine. Here again tensions occur as to the importance that Sanctorius ascribed, on the one hand, to his new methods of quantification and instrumentation and, on the other, to traditional medical methods based on logical reasoning.

Another factor that is important to consider here is Sanctorius’s social and intellectual context at the University of Padua. Sanctorius spent several years here—first as a student, and later as a professor of medicine. Prominent scholars here, in his time, who took a creative approach to innovation and tradition in the field of medicine, were Andreas Vesalius, Girolamo Fabrici d’Acquapendente, or the famous English physician and anatomist William Harvey (1578–1657), to name but a few. Their novel observations and experiences sparked controversy and—just like Sanctorius—they had to walk the tightrope between innovation and tradition. Acquapendente, who founded the Anatomical Theater in Padua, was one of Sanctorius’s teachers, and certainly also a role model for him as a student, when it came to dealing constructively with criticism of the canon. William Harvey likewise famously developed new approaches rooted in traditional lore, discovering the circulation of blood, for example—and was aware that he would therefore court controversy. Harvey and Sanctorius most likely did not meet in Padua, since Harvey studied there between 1593 and 1602, at a time when Sanctorius was a practicing physician probably in Pannonia, Croatia, and Hungary (Sect. 2.2). However, they both studied under Acquapendete, who passed his experience on to them and influenced Harvey in the development of his natural philosophy.¹² Overall, there was an intellectual climate in Padua in which the opinion prevailed that it was possible to improve on or advance traditional authorities. The establishment in Padua of the Botanical Garden (1545) and the Anatomical Theater (1595), the very first of their kind, demonstrate this openness to new knowledge and the encouragement of innovation. Most likely, this intellectual climate shaped Sanctorius in his approach to traditional and new knowledge.

To sum up, the analysis of the complex constellation in Sanctorius’s works between traditional and innovative elements revealed that the Venetian physician drew on traditional concepts when developing his novel ideas. Rather than breaking with the old, he reinterpreted and reorganized it, thereby creating something new. He brought different bodies of knowledge together in a new way: the doctrine of the six non-natural things, the concept of insensible perspiration, and previous ideas on quantification and the concept of latitudes. For him, combining quantification and Galenism was no paradox but made perfect sense. The noticeable ambiguities and inconsistencies in Sanctorius’s works indicate that he explored the limits of the existing knowledge system, provoking the traditional explanatory framework without, however, abandoning it. Sanctorius’s case therefore illustrates the complex nature of the process whereby the scientific culture and intellectual universe of a medical community began to be transformed. Namely, it sheds light on the mechanisms through which knowledge was reconfigured in the early modern period: through the conceptual reinterpretation and reorganization of existing knowledge (Siraisi 1987: 358; Renn 2020: 427). Therefore, we should not think of Sanctorius as a man divided, with one foot in modernity and one in tradition. Sanctorius understood himself to be a critical and creative physician, engaged in continuing and refining the work of the traditional authorities—Hippocrates, Aristotle, and, above all, Galen. In adding new knowledge to the old, he would not have dreamt of questioning the underlying theoretical bases. He understood his work to be “locally” new, in the specifics of his discoveries, but “globally” continuous with the objectives and methods of Galenic medicine (Distelzweig 2016: 138). In order to further identify those aspects of Sanctorius’s knowledge which moved him to reinterpret and reorganize traditional medical knowledge, and thus transform it, I have examined the entanglement of theory and practice in his works, unveiling how Sanctorius’s making and doing related to his thinking.

8.2 Theory and Practice—An Uneasy Relation

In the Commentary on Avicenna Sanctorius explained that theory had to be confirmed, a posteriori, by practice and that practice could only be understood if it was corroborated, a priori, by theory (Sect. 4.3). As a learned physician, shaped by his medical training at the University of Padua, he considered that experience gained in medical practice had to be paired with authority and reason, with medical theory, in order to be reliable. As we have seen, according to Sanctorius, a physician needed to use his hands and his head, not least to distinguish himself from the ignorant empirics and quacks. Just as innovations had to be reconciled with the basic principles of the medical tradition, so too, practical experiences had to be interpreted according to the theoretical framework of Galenic medicine. Following the Aristotelian theory of knowledge according to which certain knowledge about universal truths could be perceived only by the mind and was hidden from the senses, Sanctorius held that it was reasoning based on medical theory that ultimately led to certain medical knowledge and not experience gained through medical practice. Undoubtedly, medical theory and reasoning played an important part for Sanctorius in the purview of medicine, as was common among contemporary learned physicians (Sect. 6.2.4).

And yet, I have shown in this book that the relation between theory and practice was complex and sometimes even ambiguous in Sanctorius’s works. He rejected the division of medicine into theory and practice in the university curricula, on the grounds that medicine, contrary to theory and practice, was a “factive” or operative (factivus) art, meaning that its purpose was not truth (veritas), as it was for theory, nor action (actio), as it was for practice, but instead operation (opus), i.e., the preservation and restoration of health. Notwithstanding that medical knowledge contained, according to him, both, contemplation (contemplatio) and action, it also differed from both, due to its operative (factivus) and restorative (resarcitivus) character. Accordingly, he tried to challenge the disciplinary boundaries from within and to reform the teaching of theoretical medicine (theoria) by linking his lectures on Avicenna’s Canon to practical applications, and by confirming theory by evidence drawn from practica. The result is a seemingly peculiar mixture of highly traditional theoretical discussions with completely new elements relating to medical practice (Sect. 4.3).

In addition to this, Sanctorius occasionally challenged the Aristotelian theory of knowledge and claimed that certain medical knowledge could be generated on the basis of experience alone—through quantification and measurements. In the preface to the De statica medicina Sanctorius wrote that “not only the mind and the intellect perceive sincere and pure truth, but also the eyes and the hands virtually palpate it.” Furthermore, he described the work elsewhere as “mathematical medicine” or “static theorems” and explained that his weighing procedures were in the first degree of certainty. Along with the weighing chair, the use of his pulsilogia, thermoscopes, and hygrometers could greatly reduce elements of uncertainty in medicine, he held, since they ascertained (reddimur certi) the quantity of the deviation of a body from its natural state (Sects. 6.2.2 and 6.2.4).

Thus, by introducing instrumentation, quantification, and measurements into medicine, Sanctorius provided the physician with new “tools” that should help him gain, or at least, approximate certain medical knowledge and, more generally, improve his work. In doing so, he reorganized and reinterpreted the traditional relation between theory and practice in medicine. Especially with the De statica medicina, Sanctorius attempted to overcome the division between sensory experience and intellection. The mere idea of rendering visible by means of a mechanical instrument an inner and unseen bodily process which was completely hidden from the senses and thereby claiming to achieve mathematical certainty, shows that Sanctorius was ready to think what was by earlier Aristotelian-Galenic standards unthinkable: experience and quantification could offer knowledge about universal causes. As a true Galenist, Sanctorius was, however, at pains to distance himself from the “empirical sect” and to emphasize that his novel methods were based on learned medical knowledge. In his aim to improve Galenic medicine, theoretical medical concepts, such as dietetics or the doctrine of the six non-natural things, had necessarily to be the starting point for any inquiry into the uncertainties involved in the medical art. Against this backdrop, the ambiguities regarding Sanctorius’s attitude toward the roles of reasoning and experience, of theory and practice in medicine, dissipate and Sanctorius’s continuing confidence in the adaptability of the existing knowledge system becomes manifest (Siraisi 1987: 358).

Consequently, the results of my study not only show how the realms of theory and practice (in modern terminology) are related in Sanctorius’s works, but also suggest that the interaction of theoretical and practical knowledge played an important part in Sanctorius’s generation of new knowledge, in his innovative approach to physiology.¹³ Historical accounts of Sanctorius and his work have usually focused on his intellectual activity and thus neglected an important dimension of his endeavors—the material and practical. As has become apparent throughout this book, Sanctorius was not only an erudite university professor with a broad knowledge of the works of ancient as well as contemporary medical writers, but also and especially a diligent practitioner for whom reading books was not enough: references to dissections and surgical operations of his own, his attempt to improve dietetic-therapeutic measures and patient care through instruments such as a movable bath or cupping glasses and, of course, his development of measuring instruments all illustrate that he spent many hours at the bedside of the sick and underscore his practical expertise in a medical fields. Importantly, the aim of the various devices which he developed was to improve daily medical practice. Thus, besides theoretical knowledge related to the doctrine of the non-natural things, the concept of latitudes, or the intellectual conception of static experiments by Cusanus, Sanctorius’s practical experiences and the practical knowledge of his time shaped his novel approach to physiology.

I was able to show that, not only medical theory, but also medical practice before Sanctorius involved certain forms of quantification. There was a general awareness of the importance of regulating food intake in quantitative terms in the Renaissance and measuring meals was practiced at the time. The similarity of the De statica medicina to contemporary dietetic handbooks like the Regimina sanitatis strongly implies that the hygienic practices on which these treatises were based influenced Sanctorius in his quantitative approach to physiology and in the way in which he combined theoretical knowledge with knowledge gained from practice and observation (Sects. 4.1.2 and 5.1).¹⁴ Moreover, contemporary pharmacological practices involved a practical handling of quantities, in which doses were not computed by means of mathematical theories, but determined by hands-on testing paired with text-based knowledge. My analysis revealed that Sanctorius was very familiar with these practices and most probably frequented the Struzzo pharmacy in Venice not only to buy medicinal substances but also to exchange knowledge and experiences with the pharmacist Stecchini (Sect. 5.2.3).

Furthermore, the close examination of Sanctorius’s measuring instruments has shown that Sanctorius looked beyond the confines of medicine and was attentive to the practical technologies of the time. The investigation of moving water and the engineering problems of river control in the frame of Renaissance practical hydraulics probably inspired him in his development of an early type of a water current meter. For his hygrometers, Sanctorius most certainly drew on common experience, on shared practical knowledge, such as the contraction of hemp cords in moist air. His strong interest in mechanics, illustrated by the different steelyards he devised, was anything but ordinary for a physician. Most certainly, it evolved from Sanctorius’s socio-intellectual context, especially the Ridotto Morosini, where he met, among others, Galileo. The famous mathematician and engineer-scientist was very engaged in practical and theoretical mechanics at the time, discussing his ideas in the intellectual milieu that he shared with Sanctorius. Moreover, he used two of the same instruments that Sanctorius did—the pulsilogium and the thermoscope (Chap. 7).

In view of this, it seems plausible that Sanctorius’s interest in numerical aspects of life’s phenomena, and his subsequent application of quantification, instrumentation, and experimentation to his medical research and practice was stimulated by the practical knowledge in circulation in the vibrant milieu in which he moved, which already included quantitative aspects relating to dietetics, pharmacology, mechanics, and the use of instruments.

Last but not least, the reconstruction of the Sanctorian chair made more palpable the real world of Sanctorius’s medical practice and helped develop a deeper understanding of the practical knowledge this involved. My experiences with the replica further uncovered the way in which the material and technical aspects of Sanctorius’s endeavors played an important part in his research process. In order to achieve his goal to measure the perspiratio insensibilis, Sanctorius repurposed an old instrument and introduced weighing as a new body technology. An apparently straightforward measuring instrument became thus a complex apparatus. Sanctorius’s novel application of the steelyard raised challenges for the mechanical design and use of the instrument. In the process of transforming the steelyard into his weighing chair, and of simultaneously producing new medical knowledge about insensible perspiration, he meshed theoretical and practical knowledge and determined the course of the research. This may have resulted in his discovery of an additional use of the weighing chair: to determine how to maintain an ideal body weight. My research with the reconstruction provides thus a window onto how the encounter between medicine and mechanics served to generate new knowledge and change how knowledge was actively produced (Sect. 7.5).

To cut a long story short, Sanctorius brought together theoretical and practical knowledge from different contexts—dietetics, pharmacology, mechanics—and fused it in novel combinations. In the process, he reorganized and reinterpreted the medical system of his time, Galenic medicine, exploring to what extent quantification and measurements, as new epistemic tools, could serve to develop and to legitimize the physician’s pursuit of medical knowledge. By integrating practical and theoretical knowledge, he decidedly brought medical practice into the realm of medical theory, which is best illustrated by his inclusion of instruments in his teaching of physiology, a highly theoretical discipline, in his day. Still, according to him, the physician was both a philosopher and an artist and thus Sanctorius, the learned Galenist, and Sanctorius, the diligent practitioner, existed side by side. Similarly, his work highlights both the elasticity of Renaissance Galenism and the incremental shifts in views of how the human body functions. His novel approach to physiology was a response not only to changing medical ideas and practices, but also culturally driven—by the contemporary enthusiasm for instruments and measurements and by concerns and habits regarding health advice. After this reflection on the epistemic constellations that led Sanctorius to produce new knowledge, I will now turn more specifically to his use of measuring instruments in medicine and briefly consider what has been learnt from their analysis.

8.3 Quantifying Health

Wind, water currents, pulse, body heat, humidity of the air, insensible perspiration—as this book has shown, the spectrum of parameters that Sanctorius proposed to measure and for which he developed instruments is quite impressive. Over the course of Chap. 7, it was demonstrated that it is often difficult to assess whether Sanctorius’s various measuring devices actually worked and could be used in the way he described them; and in the same vein, to what extent Sanctorius used them in his daily medical practice, and on how many different people, frequently remains unclear. With the exception of the weighing procedures with the Sanctorian chair, the Venetian physician hardly ever referred to the numerical outcomes of his measurements. And even in the De statica medicina, compared to the overall length of the treatise, only a fraction of aphorisms specify quantitative values.

This lack of numerical data might be explained by the impossibility of producing them. Another aspect to consider in this regard is that Sanctorius often directed his readers to his proposed but never published book De instrumentis medicis for more information on his instruments and quantitative observations. However, the scarce remarks on quantitative data might also point to the way in which Sanctorius conceived and used his instruments: as comparators. In this connection, the dissemination of precise quantitative measuring results and the elaboration of uniform scales most probably took a backseat. What was important was that the physician always used the same instrument with the same scale for an individual patient in order to make the measurements comparable and to monitor health trends. Although Sanctorius did not state this explicitly, with regard to his thermoscopes, he pointed to the fact that different instruments would produce different measuring results. He repeatedly indicated that, due to the considerable differences between individual patients, it was very difficult to generalize measurements and make them applicable to many individuals. In view of this, concrete measuring results could indicate general tendencies, but a physician would nonetheless always have to take measurements of his own, of his specific patient and using his specific instruments. Even though Sanctorius explained in the Commentary on Galen that he used his pulsilogium, the thermoscope, and the weighing chair to assess the condition of a patient whom he had never seen before, he immediately qualified this statement in the next sentence by explaining that he believed, along with Galen, that the exact and specific quantity will not be comprehended by the physician. This implies that Sanctorius used his measuring instruments to generalize, if necessary, but was fully aware of the shortcomings of such a procedure. Against this backdrop, his silence on the quantitative results of his measurements appears in a different light—they were simply of secondary interest (Sanctorius 1612b: 376).

The preceding paragraphs have demonstrated that it is crucial to not isolate Sanctorius’s measuring instruments from their original medical context. In fact, it is exactly this context that makes Sanctorius’s undertakings special. Notwithstanding that he mostly based his devices on well-known phenomena and techniques such as the oscillation of the pendulum, or weighing, it was he who first applied these to medical diagnosis, prognosis, and therapy—be it in thought or in deed. Therefore, the measuring instruments and their use can be understood only when considered in the framework of contemporary Galenic medicine. As was seen, Galen’s concept of latitudes provided the starting point for Sanctorius’s innovative idea of measuring deviations from the natural, healthy state of a body by means of his four most famous instruments. Although Sanctorius, in doing so, significantly departed from traditional medical theory and practice, his measurements must still always be related to these. Thus, his use of pulsilogia was deeply embedded in contemporary pulse theory, according to which the pulse frequency was but one of several parameters that indicated to a physician his patient’s state of health. Similarly, the thermoscopes allowed Sanctorius to replace the subjective appreciation of body heat by means of touch, but in the face of traditional fever theory, it was not enough to determine the degree of heat in a patient to diagnose the disease. The impact of measured degrees of air’s humidity on the body could only be understood when knowing the individual complexions of people living in a certain region, and even here many differences occurred. In order to define a healthy excretion of insensible perspiration, Sanctorius considered it necessary to examine the effects of the six non-natural things on this bodily evacuation. Hence, on the one hand Sanctorius ascribed a very important role to the quantitative observations which he made with his measuring instruments, but on the other, he considered them as new techniques of Galenic medicine, as complementary methods that mostly added to traditional, qualitative procedures and only occasionally replaced them. Sanctorius did at times aspire to a medical practice more systematically informed by quantification, but as the foregoing analysis has revealed, he did not consistently formulate a quantitative medical program. To be sure, quantitative methods played an important part in his medicine, but they were far from being wholly constitutive of it. Experience, measurements, and instruments served Sanctorius as a means to refine prior theory (Ragland 2017: 505, 527).

In this regard, it should be remembered that Sanctorius designed his instruments to enhance the certainty of medical knowledge with the aim of improving the practical work of physicians. This implies that he addressed his quantitative studies exclusively to colleagues. The inclusion of the illustrations and descriptions of his measuring instruments in the Commentary on Avicenna, an extensive medical textbook, further corroborates this assumption. It seems that Sanctorius held that every physician needed his devices in his daily practice. Accordingly, not the devices themselves, but their use was the main focus of attention. Operating these measuring devices called not for details of how they worked, but rather manual skill—this was far more important at the time than technological or mechanical knowledge. This might then explain why Sanctorius did not reveal more technical details of his devices and limited his descriptions of them to purely medical applications. However, in the 1626 edition of the Commentary on Avicenna, he stated that he had not published illustrations of his pulsilogium in previous works, since to properly convey to the reader how to build the device would require many plates; and this is why he decided to postpone a detailed description and illustration of the instrument until the work De instrumentis medicis (Sanctorius 1626: 21). From this it would appear that Sanctorius thought his readers, most of them physicians, capable of understanding the technical and mechanical details of his pulsilogium, if they just had enough detailed illustrations. Yet, evidently, Sanctorius and his fellow physicians, too, relied on the support of craftspeople to build the medical measuring instruments. Unfortunately, there are no sources regarding whether Sanctorius had assistants, not to mention their identities, and it is only by analyzing the material, practical dimensions of Sanctorius’s work that we can seek to uncover their contribution to his quantitative approach to physiology.

With the weighing chair Sanctorius seems to have gone even a step further. The instrument not only enabled physicians to observe their patients’ insensible perspiration of, but also offered laymen the opportunity to find and maintain an ideal weight. To this end, the weight watcher needed neither understand the mechanical properties of the device, nor have expert medical knowledge, as my own experimentation with the reconstruction illustrated. Even though it sometimes seems as if Sanctorius invited his readers in the De statica medicina to perform the weighing procedures themselves (Sect. 5.4.1), the treatise reads not so much as a guide to experimentation, but rather as a dietetic handbook for physicians, students, or other well-educated persons fluent in Latin (Sect. 4.1). In all likelihood, it served Sanctorius to demonstrate his authority and expertise (Steinle et al. 2019: 8). However, eleven years later, with the illustration and description of the weighing chair in the Commentary on Avicenna, Sanctorius seems to have been ready to ascribe some authority to his readers: to physicians, the observation of the perspiratio insensibilis in their patients, and to patients, the monitoring of their own body weight. In doing so, he ascribed authority also to another actor—the Sanctorian chair.

Turning to the impact of Sanctorius’s works, it is interesting to note that a preliminary assessment regarding the reception of his measuring instruments suggests that they did not widely enter medical practice, let alone the household. Testimonies of Sanctorius’s pupils and contemporary physicians show that there was a great interest in his devices, and scholars all over Europe made their own copies of them. Yet, these undertakings were often not related to medicine, but to other fields of study. Isaac Beeckman, for example, drew inspiration from Sanctorius’s pulsilogia for his observations on vibrating chords. Agostino da Mula informed Giovan Francesco Sagredo about Sanctorius’s thermoscopes not because the latter was interested in their medical application, but in the instruments per se. Even a century later, at the beginning of the eighteenth century, Giovanni Battista Morgagni approved of Sanctorius’s quantitative approach to physiology, but I could find no evidence that he himself used a pulsilogium or a thermometer in his medical practice. Hygrometers, anemometers and other instruments to measure climatic conditions never gained a strictly medical identity. Only much later did the fever thermometer and bathroom scales find their way into medical practice and the household. All this implies that integrating Sanctorius’s measuring instruments into medical practice was a lengthy process; indeed, the revised and novel versions of only some of his instruments eventually succeeded on this path.

Hence, contrary to what the new mechanistic vision of the body that evolved in the seventeenth century might lead one to expect, quantitative measurements with thermometers, balances, or pulsilogia did not gain in importance, either in diagnostics or everyday general medical practice. Quite the reverse, in fact: as Volker Hess has shown with regard to the thermometer, the concepts of fever the seventeenth and eighteenth centuries made the measurement of body heat a mere secondary interest (Hess 2000: 19–33). Only in the nineteenth century did the measurements of pulse, body temperature, and weight start to become established as standard diagnostic methods.¹⁵ The conceptual framework in which these practices and their attendant instruments gained importance was, of course, far removed from the one in which Sanctorius first proposed their use. That this may have given rise to an anachronistic reading of the original instruments owing to their roots in the Galenic medicine become obsolete for the later devices, has been often overlooked or neglected by historians. But my study has clarified how important it is to apprehend knowledge related to technical instruments and to the practices surrounding them in its historical specificity, for only so can one understand and make sense of how knowledge was transformed in earlier times. Thus, to separate Sanctorius’s measuring instruments from their Galenic context is to lose their historical meaning. Indeed, the late application of thermometers, scales, and pulse meters to medical practice fits with the more general historiographical observation that practices associated with the body in sickness and in health tend to be particularly resistant to the innovation and change forged by new scientific theories or discoveries (Stolberg 2012: 519).

Contrary to this, with respect to medical research, Sanctorius’s quantitative approach to physiology, especially his method of investigating the perspiratio insensibilis, immediately fell on fertile ground. Sanctorius’s novel ideas paved the way for subsequent scholars to a mathematical and experimental analysis of physiological and pathological phenomena. Dissatisfied with the concepts of traditional Galenic medicine, these scholars were inspired by Sanctorius’s novel approach in their creation of new medical theories. In the process, Sanctorius’s name became inextricably linked to the quantitative investigation of the perspiratio insensibilis and his research method, weighing, was used until as late as the twentieth century.¹⁶ It seems ironic, in hindsight, that Sanctorius set the stage for a new medical science in which medical practice remained largely unchanged—the very opposite of what he intended.