The Scope Announced on the Title Page
The Traité des fiévres continues addresses a category that early-modern medicine kept sharply apart from intermittent fevers. A continued fever, in the Galenic and Hippocratic scheme still governing eighteenth-century practice, is one that does not leave the patient between paroxysms: the heat, the pulse, the altered urine, the state of the tongue and the countenance persist without true remission. Quesnay’s announced programme is not to add a new species to the nosology but to gather and weigh what the ancients established about such fevers “par l’observation & par la pratique,” and specifically about four things: prognostics, coction, crises, and cure. That list is the spine of the work. It is a learned treatise before it is a clinical manual — an examination of testimony, in which Hippocrates, Galen and the later commentators are quoted, compared and sifted.
The book’s method follows from that subtitle. Quesnay does not proceed by inventing a system and deducing fevers from it. He assembles the recorded observations of the Greek physicians and asks what can be retained from them. The result is a work of medical erudition as much as of bedside practice, marked by close reading of the Prognostic, the Aphorisms, the Epidemics and the Coan prognoses, and by constant reference to what the older practitioners had seen happen in fevers.
Prognostics: Reading the Course of the Disease Before It Turns
The treatise opens its substantive work with the question of signs. Ancient fever medicine rested on the assumption that a continued fever runs a determinate course, and that the physician’s first task is to say, from the appearance of the patient and the character of the excretions, whether that course will end well. Quesnay works through this material in detail: the significance of the countenance, the state of the eyes and nostrils, the position of the body in bed, the picking at the bedclothes, the character of the respiration, the condition of the tongue, the colour and consistency of the urine, the appearance of the stools, the sweat.
What interests him is not a catalogue of ominous signs for its own sake but the logic connecting sign to outcome. A sign is prognostic because it indicates the state of the humours and the strength of the natural powers; it tells the physician whether the fever will resolve by a favourable evacuation or degenerate into a putrid or malignant state. The treatise therefore treats prognosis as part of the science of fever, not as a separate art of fortune-telling, and it defends the Hippocratic claim that the physician who can predict the course of a disease is the one who can also direct its treatment.
Coction and the Maturation of the Humours
The central theoretical chapter of ancient fever medicine, and the one that takes up most of Quesnay’s attention, is coction — the “concoction” or ripening of the morbific matter. On this doctrine, the fever-heat is not simply an enemy to be extinguished but the instrument by which the body works the offending humour into a state from which it can be expelled. Raw, uncocted matter produces the worst fevers; the appearance of coction in the urine, in the sputum, or in a sediment, is the sign that nature is winning.
Quesnay expounds this doctrine at length and, in doing so, stakes out a position. He is defending the Hippocratic account of fever as a regulated process with a natural term against those who reduced fever to a merely disordered motion of the blood or to a fermentation in the humours, and who consequently saw coction as so much mystical verbiage. The argument requires him to explain what coction actually is — a change in the consistency and quality of the humours, brought about by the heat of the fever and directed by the economy of the living body — and to answer the objection that no such process can be observed. His answer rests on the visible evidence of the excretions, which change character as the fever advances and which the ancients had learned to read.
Crises and the Days on Which They Fall
From coction follows crisis: the sudden turn of the disease when the matured matter is discharged and the fever resolves. The treatise examines the classical doctrine of critical days, the observation that crises fall on certain days of the illness — the fourth, seventh, eleventh, fourteenth, seventeenth, twentieth — and not on others, and that the intervening days are typically worse. It also examines the ways in which a crisis occurs: by sweat, by copious urine with sediment, by diarrhoea, by nosebleed, by a haemorrhoid, by the appearance of an abscess or a parotid swelling.
Quesnay treats these not as superstitions but as the accumulated observations of practitioners, and his concern is to show why the periodicity should hold: if the fever is a work of coction proceeding at a determinate pace, then the moment at which the matter is ripe will also be determinate, and the crisis will fall where the arithmetic of the illness puts it. He is careful to distinguish favourable crises from imperfect or dangerous ones, the “crise imparfaite” that leaves the disease unfinished and liable to relapse, and to distinguish true critical evacuations from the merely symptomatic sweats and stools that occur at any time.
The Cure: Evacuation, Bloodletting, and the Support of Nature
The therapeutic portion of the work draws the consequences. If the fever is a natural effort at coction, the physician’s business is to assist rather than to interrupt it. Quesnay sets out the indications for and against bleeding, the use of purgatives and enemas, the management of the critical evacuations, the regulation of diet and drink, the value of diluents and acidulated drinks, and the treatment appropriate to the various stages of the disease. He is attentive to the timing that the whole theory implies: an evacuation forced before coction is achieved weakens the patient without shortening the illness, while one withheld after the matter is ripe prolongs it.
The treatise also takes up the several varieties of continued fever recognised in the medicine of the period — the inflammatory synochus, the burning causus, the putrid and the malignant fevers — and asks how far the general doctrine of coction and crisis applies to each. The complications of fever, and the question of when a continued fever passes into a state that the ancients called malignant, belong here as well.
Quarrelling with the Moderns
Running through both volumes is an argument about authority. Quesnay is not a mere compiler; he is defending a body of ancient knowledge that the mechanical and chemical schools of the late seventeenth and early eighteenth centuries had attacked as incoherent. The iatromechanists, who explained fever as a disturbance of the size and motion of the blood particles, and the iatrochemists, who explained it as an acid or alkaline fermentation, both had reason to discard coction and crisis as fables. Quesnay answers that the ancient observations were made at the bedside over centuries, that they are confirmed in practice, and that the modern systems, whatever their elegance, have not produced better results.
His own account of the “économie animale” gives the ancient doctrine a physiological footing: the body is a system of solids and fluids in which the tonic state of the fibres and the condition of the humours are mutually dependent, and fever is the reaction of that system to whatever obstructs or corrupts its ordinary movement. The book thus belongs to the quarrel of the ancients and moderns in medicine, and it takes the ancient side while trying to show that the ancient side is not incompatible with a reasoned physiology.
The two volumes close with indexes of the matters treated, so that the mass of citation can be worked through by topic — a fitting end for a book whose real labour is the ordering and assessment of inherited testimony rather than the announcement of a new discovery.
Prognosis and the Reading of Signs
The treatise gives prognosis a central place. The distinction between favourable and imperfect crises is, in practice, a prognostic distinction: the physician must judge from the signs of coction whether the disease is moving toward a true crisis, whether the critical effort will be incomplete, or whether danger is increasing. Quesnay’s defence of the ancient doctrine depends on the reliability of such signs; if they can be read and if they predict the event, the theory of coction is confirmed at the bedside. The book is thus as much a work of semiology as of therapeutics — it teaches how to interpret the course of a continued fever before acting.
Definition, Classification, and the Use of Authority
Another strand is the effort to fix the meaning of terms. Quesnay examines what is meant by a continued fever, by coction, crisis, putridity, and malignity, because he sees that much of the dispute between ancients and moderns turns on equivocal language. His method is to set received opinions against the observed sequence of the disease and to retain what is clinically useful. The significance of the book lies in this discipline: it is a defence of Hippocratic medicine conducted through physiological reasoning and prognostic judgment, not through mere deference to antiquity. It treats medical theory as an aid to judgment, and its erudition is ordered to that end.
