Initial Poisonings from the Abuse of Psychic Stimulants: Jules Héricourt’s Perspective

1. Introduction

The abusive use of substances such as alcohol, tobacco, tea, and coffee is a growing concern in many European societies. Although these substances are socially accepted and widely consumed, their excessive use can have serious impacts on both physical and mental health.

Tobacco is a common substance whose abuse represents a significant public health threat. Smoking is associated with a range of serious diseases, including lung cancer, cardiovascular and respiratory diseases, and contributes to environmental pollution and the depletion of natural resources. Among World Health Organization (WHO) regions, Europe has the second-highest prevalence of tobacco use among adults (25.3%) and adolescents (10.8%) (WHO, 2025a). By 2030, Europe is projected to have the highest rate globally, with around 23% of adults smoking (WHO, 2025b). The tobacco industry is among the main contributors to preventable deaths in Europe, with over 1.15 million estimated deaths per year (WHO, 2024a).

Alcohol is one of the most widely consumed psychoactive substances across Europe. While enjoyed by many as part of social and celebratory culture, excessive alcohol consumption can lead to a range of health problems, including liver injury, increased risk of cardiovascular disease, mental disorders, and dependence. In the WHO European Region, adults consume, on average, 9.2 litres of pure alcohol per year, making them the highest consumers worldwide (WHO, 2024a). Approximately 11% of adults in this region experience alcohol-related disorders, and around 5.9% live with alcohol dependence. Alcohol consumption is associated with at least seven types of cancer, including breast and colorectal cancer, and accounts for one-third of cancer-related deaths in the European Union (WHO, 2024a). In 2021, the WHO Europe estimated approximately 426,000 annual deaths attributable to alcohol consumption (WHO, 2024b).

Although tea and coffee are considered socially acceptable, and even health-promoting when consumed in moderation, excessive consumption of these substances may also have negative consequences. Consumption of more than four cups of coffee per day has been associated with a 17% reduction in the risk of head and neck cancers (Nguyen et al., 2024) and reduced bone density (Hallström et al, 2013; Zeng et al., 2022), whereas high consumption (≥5 cups/day) has been linked to an increased likelihood of ischemic stroke (Smyth et al., 2024). Evidence is less clear for tea, but results suggest that drinking one cup per day or less is associated with a 9% lower risk of head and neck cancers overall (Nguyen et al., 2024) and a reduced risk of stroke (Smyth et al., 2024). Excessive caffeine intake may cause symptoms such as insomnia, anxiety, irritability, and palpitations (Jin et al., 2016; Shirlow & Mathers, 1985). Furthermore, overconsumption of tea and coffee can lead to gastrointestinal issues and interfere with the absorption of certain nutrients.

Slow carbon monoxide intoxication is a silent threat that may occur in homes, often without the inhabitants’ awareness. The danger of carbon monoxide poisoning lies in the fact that its symptoms are frequently confused with other conditions, such as influenza or fatigue, which can result in misdiagnosis and prolonged exposure to the gas (Williams et al., 2025).

This study aims to analyze Jules Héricourt’s ideas regarding early intoxications, particularly those caused by the abuse of psychoactive stimulants and by carbon monoxide exposure, as conveyed in the early twentieth century.

2. Materials and Methods

This study adopts a qualitative, historical-documentary approach, focusing on the analysis of medical conceptions presented by Jules Héricourt in the early twentieth century. The research is based on the critical examination of primary and secondary sources, seeking to historically contextualize the author’s medical thinking and understand how he interpreted the pathological processes associated with the consumption of substances such as alcohol, tobacco, tea, and coffee. This type of investigation is particularly suitable for examining scientific ideas within their social, cultural, and institutional context, enabling an understanding of the evolution of medical and scientific thought over time (Bowen, 2009; Denzin et al., 2023).

The analysis primarily focused on the second book of Les Frontières de la Maladie (Héricourt, 1904), in which Héricourt discusses intoxications of external origin related to the abuse of psychoactive stimulants and exposure to carbon monoxide. Other works and publications by the author were also considered to contextualize his scientific output and positioning within the field of experimental medicine. Additionally, secondary sources – including historiographical studies, works on the history of medicine, and contemporary scientific literature on psychoactive substance consumption and intoxications – were used to situate Héricourt’s interpretations within the scientific landscape of the period and establish a dialogue with current knowledge.

Document analysis followed the principles of qualitative content analysis as proposed by Bardin (1977), developed in three main stages: pre-analysis of sources; material exploration; and processing and interpretation of results. To ensure research consistency, source triangulation procedures were adopted, simultaneously consulting historical documents and current scientific literature. Historical and epistemological contextualization helped mitigate potential anachronistic interpretations, respecting the conceptual frameworks of contemporary medicine (Kragh, 2003; Goodson & Sikes, 2001). Moreover, fidelity to the author’s original formulations was maintained, employing critical translation of original text excerpts where necessary.

3. Results

3.1. About the Physician and Physiologist Jules Héricourt

Jules Héricourt (Figure 1) was born into a working-class family in Paris at 11:00 on 12 March 1850. He was registered as the son of an unknown father and Evelina Geneviève Héricourt, who was 19 years old and unemployed at the time (Paris Archives, 2025a). He later married Marie Françoise Marandet. He died, widowed, at 12 rue Douai, in the 9th arrondissement of Paris, specifically in the Saint-Georges district, aged 87, on 24 January 1938, with the death certificate issued the following day by Henri Bornens (Paris Archives, 2025b).

From 7 November 1869, Jules Héricourt attended the Military School of Health in Strasbourg1. Three years later, he commenced the academic year at the Val-de-Grâce School of Application2, where, in 1874, he undertook his medical internship (ANF, 2025). In this capacity, on 28 January 1874, Jules Héricourt submitted his doctoral thesis in Medicine to the Faculty of Medicine at the University of Paris, entitled Quelques considérations sur les maladies du soldat en garnison (Bibliothèque Nationale de France, 2025).

Later that same year, on 21 July 1874, Jules Héricourt was appointed Deputy Major Physician, 2nd Class3, at the Hospitals of the Constantine Division4. Four days later, he was transferred to the Military Hospital of Sétif5. While in this position, he was promoted to Deputy Major Physician, 1st Class, on 31 December 1876. From this date, he was assigned to various units (Foot Chasseur Battalion, Artillery Regiment, Sapper-Firefighter Regiment) until his promotion, on 5 October 1892, to Major Physician, 2nd Class, and his posting to the 118th Infantry Regiment. Subsequently, he served in several other military units, including the Military Hospital of Lille6 (ANF, 2025).

On 13 September 1885, his resignation was accepted, and he was transferred to the Territorial Army attached to the Field Hospital on 15 March 1886, with the rank of Major Physician, 1st Class. On 17 January 1900, his resignation from the army was accepted, though he was reinstated for the duration of the war and assigned to Villemin Hospital (ANF, 2025).

From September 1885, he served as secretary of the editorial board and as an author for the Revue scientifique, also contributing to the Revue de Médecine, the Revue des Deux Mondes, and the Revue Philosophique (ANF, 2025).

Charles Robert Richet (1850-1935) was born in Paris into a wealthy and socially prominent family. He was the son of Louis Dominique Alfred Richet (1816-1891), a renowned surgeon and professor in the Department of Surgery at the Faculty of Medicine, University of Paris, as well as Chief Surgeon at Hôtel-Dieu Hospital, and a friend of Claude Bernard (1813-1878), widely regarded as the founder of experimental medicine. During his studies at the prestigious Lycée Bonaparte, Richet developed an interest in parapsychology and became friends with Jules Héricourt.

Following the reforms of Napoleon III and the Third Republic, which strengthened experimental medicine, the Faculty of Medicine at the University of Paris had multiple laboratories and chairs. The Physiology Laboratory was strongly linked to the Claude-Bernardian tradition, focused on experimentation with animals and the search for physiological laws. This laboratory was among the first to test serum as a treatment (prior to Behring and Roux popularizing the antitoxic serum against diphtheria), and the experiments conducted there anticipated some discoveries of modern immunology, albeit without contemporary terminology.

Charles Richet is emblematic of faith in scientific progress and the epistemology of his experimental method, inherited from Claude Bernard, Aristide Auguste Stanislas Verneuil (1823-1895), and Marcellin Pierre Eugène Berthelot (1827-1907), which he frequently developed and commented on personally. Bernard’s Introduction to the Study of Experimental Medicine (1865) was decisive, recognizing him as his intellectual mentor and regarding himself as a continuator of a scientific tradition based on rigorous observation and controlled experimentation. In 1878, Charles Richet became adjunct professor of physiology, inheriting part of Bernard’s teaching tradition and assuming directorship of the laboratory, which followed the Bernardian approach to physiological experimentation with animals.

In 1887, Jules Héricourt joined Charles Richet in his laboratory, and for fifteen years they conducted numerous studies together. Héricourt investigated the effects of antibody treatments and undertook early attempts to combat cancer through serotherapy (Androutsos et al., 2011). From 1 October 1889, Jules Héricourt assumed the position of Deputy Head of the Physiology Laboratory at the Faculty of Medicine, University of Paris.

Jules Héricourt was a proponent of microbial theories. In 1888, he published an article with Charles Richet indicating that haematotherapy could be employed to treat infectious diseases. Their studies on tuberculosis led them to propose treatment of patients with zomotherapy (raw meat) (Watier, 2009).

Héricourt was a close friend of Émile Zola (Héricourt, 1890), testifying on his behalf during Zola’s trial in February 1898 following his “J’accuse” column in the Dreyfus Affair (Lahaie, 2016). Maurice Feuillet (1873-1968) commemorated this historic moment of Héricourt’s humanist commitment with a graphite sketch on woven paper in 1898 (Musée d’Art et Histoire du Judaïsme, 2025). In the same year, the Ligue des Droits de l’Homme was established, with Jules Héricourt as one of its founders and vice-presidents (Naquet, 2016). Between 1904 and 1934, concerned with social issues, he dedicated himself to supporting low-income populations as director of an anti-tuberculosis dispensary.

Jules Héricourt was a great admirer of Louis Pasteur (1822-1895). Héricourt published an early scientific review on the pathogenic role of microbes in 1884, popularizing Pasteur’s theories while studying agents of cholera and tuberculosis. It is also established that Héricourt had personal contact with Pasteur (Lahaie & Watier, 2017).

On 16 May 1933, the Academy of Medicine awarded Jules Héricourt the Albert of Monaco Prize, endowed with 100,000 francs (Téry, 1933), equivalent to approximately €192,000 today. The newspaper L’Oeuvre had anticipated the award fifteen days earlier, given the near certainty of the decision. Nonetheless, the selection generated some controversy. Of 79 votes, 59 were for Jules Héricourt; two for Raymond Jacques Adrien Sabouraud (1864-1938), a French physician specialized in dermatology and medical mycology, notable for pioneering research on fungal skin diseases; one for Emil Adolf von Behring (1854-1917), a German physician, bacteriologist, and immunologist, renowned as the “savior of children” and the first Nobel laureate in Physiology or Medicine, 1901. Finally, 17 ballots were blank, reportedly issued by the Pasteur Institute in protest (Téry, 1933).

On 30 July 1894, by decree based on the Minister of the Interior’s report, Jules Héricourt was appointed Knight of the Legion of Honour, with Charles Richier as his sponsor. On 11 March 1918, he was awarded the Officer’s Cross of the National Order of the Legion of Honour, entitled from that date to wear the insignia and receive associated benefits (ANF, 2025).

The work of Charles Richier and Jules Héricourt, despite some contestation and disputes over authorship within the scientific community, contributed to the emergence of a new discipline – Immunology – even if they were unable to translate this knowledge into medical applications, neither for tuberculosis nor cancer, though recognizing its potential in immunotherapy (Lahaie & Watier, 2017). Both authors may be regarded as representatives of the so-called “physiologisation of Pasteurism” movement, leading to the birth of immunology: understanding immune responses, applying physiological approaches to medical treatments, and preventing disease (Bonito, 2022).

3.2. On the Abuse of Psychic Stimulants

Jules Héricourt authored numerous works, notably Quelques considérations sur les maladies du soldat en garnison (1874), La contagion par les insectes, un nouveau chapitre de pathogénie animée (Edition A. Davy, 1899), La sérothérapie; historique, état actuel, bibliographie (Edition J. Rueff, 1899), Zomotherapy; its origin, its statistics, its technical application, its action, its indications and contra-indications (Edition J. Rueff, 1906), L’hygiène moderne (Edition Ernest Flammarion, 1907), Les 36 commandements de l’hygiène (Edition La Revue, 1911), Les maladies des sociétés, tuberculose, syphilis, alcoolisme et stérilité (Edition Ernest Flammarion, 1918), among others.

In 1904, Héricourt published Les frontières de la maladie: Maladies latentes et maladies atténuées (Ernest Flammarion), which reached 29 editions by 1920 in French, Albanian, Asturian, Castilian, and English, and is held in 82 WorldCat member libraries worldwide (WorldCat, 2021). Structured into six books and 24 chapters, the work focuses on cases where the boundary between health and disease is ill-defined, with transitions occurring imperceptibly.

Héricourt (1904) begins by asserting that, like self-intoxications and toxemias of internal, cellular, or intestinal origin, exogenous intoxications may manifest in all degrees, typically established slowly and persisting for extended periods at low intensity, often in mild and inconspicuous forms. The maintenance of certain lifestyle habits led to continuous poisoning until accidents, sometimes severe, prompted the individual to seek medical advice.

Without aiming to be exhaustive, Héricourt (1904) addresses the most common intoxications resulting from moral and socially influenced habits, referring to the use of alcohol, tobacco, tea, and coffee, as well as contemporary lighting and heating methods, which were often so faulty as to cause numerous accidents.

3.3. Mild Alcoholism

Héricourt (1904) first refers to “mild alcoholism”. By the early twentieth century, alcohol abuse had already caused considerable harm in France. He distinguishes disorders directly due to alcohol (spirits such as brandy, rum, cognac, kirsch, whisky, gin) from those resulting from habitual wine consumption or beverages containing essences, introducing the concepts of ethylism, and absinthism. Ethylism denotes a pathological state induced by prolonged and excessive consumption of ethyl alcohol, encompassing both acute intoxication (inebriation) and chronic dependence. It represents a disease resulting from habitual excessive intake of alcoholic beverages, particularly wine.

Absinthism refers to excessive or habitual consumption of absinthe, a potent alcoholic beverage (generally 45-74% ABV) made from fennel, anise, and principally Artemisia absinthium7 (Farlex, 2025). In the nineteenth and early twentieth centuries, absinthe was popular, especially in France and Switzerland, associated with artistic and intellectual bohemia. Excessive consumption was linked to both physical and mental health issues, giving rise to the term absinthism, used to describe harmful effects such as hallucinations, seizures, dependency, and symptoms akin to alcoholism. Absinthism can thus be understood as a specific form of alcoholism, particularly associated with absinthe and its toxic effects, notably due to thujone8 (Höld et al., 2000). Today, although absinthe is again produced and consumed in some countries, the concept of absinthism remains primarily historical and cultural.

Héricourt (1904) excludes acute accidents from overconsumption, since although these produce temporary intoxication (inebriation), they are fleeting. Instead, he analyses ethylism for its slow, subtle, and deceptive development, typically without evident initial symptoms, yet capable of progressing to severe stages. Early manifestations include digestive and nervous disturbances: reduced appetite, laborious digestion, epigastric heaviness and burning, and morning nausea.

In more advanced stages, still not alarming to the consumer, sensory disturbances begin to appear in the lower limbs, less frequently in the upper limbs, such as tingling and prickling sensations, more intense at night and regionally localized on the soles, fingertips, and around the joints. Skin may develop symmetric analgesia after initial hyperaesthesia, gradually extending from feet to legs and thighs, while tactile and thermal sensitivity remain intact. Muscle strength declines, and tremors appear – initially transient and restricted to the morning – becoming more permanent and exacerbated by precise movements.

Mental disturbances include insomnia, dreams, and nightmares: sad dreams and terrifying nightmares. Héricourt (1904) notes that even patients only slightly affected by alcohol may develop delirium during acute illness and display heightened vulnerability to nervous or cerebrospinal forms of infectious diseases, to which they have diminished resistance.

Regarding enolism, the initial disorders are like those already described. Héricourt (1904) draws on Étienne Lancereaux (1829-1910), renowned for pioneering contributions to the understanding of diabetes. According to Lancereaux, enolism symptoms are compounded by the action of potassium salts on the abdominal viscera, particularly the liver and spleen, inducing apparent congestion and potentially causing signs of hepatic insufficiency.

As for absinthism, or ousism – as Lancereaux termed it – the author observed consumption escalating to levels that raised public concern in France, due to poisoning from various aperitifs, bitters, and liqueurs. In early twentieth-century France, alcohol consumption was intertwined with café, bistro, and literary salon culture. Aperitifs, bitters (amers), and liqueurs formed part of this social milieu. Examples of aperitifs of the period include: Absinthe, the most famous, emblematic of the artistic bohemia until banned in 1915; Pastis, which emerged as its substitute and was regulated in the 1930s; Byrrh, a red wine-quinine blend, popular until the 1930s; Dubonnet, fortified wine with quinine, favored by conservative clientele; Lillet, an aromatized wine from Bordeaux (white version often served with ice and lemon peel); Noilly Prat, dry vermouth from Marseille, consumed neat or in cocktails.

Bitters (amers) were herbal infusions often used as digestive tonics or bases for aperitifs. Examples include Picon, a bitter orange-quinine-gentian aperitif, popular in Alsace-Lorraine and often mixed with beer (“Picon bière”); Fernet, Italian in origin but consumed in France as a bitter digestif; Suze, created in 1889 from Gentiana lutea, an icon of the Belle Époque; and Amer Bière, a generic bitter beer mix.

Liqueurs are sweeter and typically consumed after meals (digestifs) or used in confectionery and cocktails. Examples include Chartreuse, a liqueur made by Carthusian monks with over 130 herbs, available in two main varieties: green (stronger) and yellow (sweeter); Bénédictine, an herbal and spice liqueur produced since the nineteenth century in Fécamp, associated with the elegance of the period; Curaçao, a citrus-flavoured liqueur (notably “Triple Sec”) used in cocktails and confectionery; Crème de cassis, a sweet blackcurrant liqueur, the base of the famous Kir cocktail (mixed with white wine); and Anisette, an anise-flavoured liqueur, sweeter than pastis, typically consumed with water.

Consumption of these products produces effects broadly similar to the onset of ethylism, though distinguished by pronounced nuances. Héricourt emphasises that these are primarily sensory disorders of the limbs, symmetrical with an ascending tendency, manifesting as hyperalgesia—excessive reflexes and heightened pain sensitivity.

3.4. Caffeine Consumption

Héricourt (1904) notes that many individuals consumed coffee excessively, often three or more times per day. Coffee, however, was far from innocuous. In addition to caffeine – a potent alkaloid – it contains aromatic compounds, tannins, and potassium salts, whose effects are additive with caffeine. Excessive intake may cause impatience, tremors, dizziness, palpitations, and insomnia; headaches, vomiting, and severe diarrheal episodes may also occur.

More important than acute manifestations are the chronic effects resulting from prolonged overconsumption of coffee or tea. Symptoms include epigastric heaviness, slow digestion, loss of appetite, and constipation, often accompanied by general weakness, reduced motivation, low mood, and sleep disturbances. While Harcourt does not address dependence, many of these symptoms temporarily resolve after further coffee intake, reappearing as the stimulant effect diminishes.

Chronic overconsumption may induce rhythmic tremors, muscular spasms, rapid, weak, and irregular pulse, and dizziness. Over time, consumers may become melancholic and restless, reporting diffuse pain, neuralgia, pruritus, and various skin eruptions. Muscle strength declines, and weight loss may occur. Some authors attributed impaired vision in adults over 45-50 years, especially in Arab populations, to “caffeinism”.

Héricourt observes that coffee consumption appears less harmful in warmer climates; for instance, individuals in Algeria could tolerate relatively high coffee intake but developed caffeinism symptoms upon returning to France. Similarly, some could only tolerate coffee in summer, substituting tea in colder months. He concludes that these two stimulants – tea and coffee – seem better suited to different climatic conditions, with coffee preferred in warmer regions and tea in colder ones.

Héricourt (1904) therefore concluded that all evidence indicated these two stimulants – tea and coffee – appeared to be better suited to different climatic conditions. Interestingly, he noted that coffee was the customary beverage of people in warmer regions, whereas tea was preferred by inhabitants of colder countries.

3.5. Tobacco Consumption

By the late nineteenth century, it was known that environmental tobacco smoke contained a complex mixture of chemicals, including nicotine, carbon monoxide (CO), carbon dioxide (CO₂), ammonium cyanide (NH₄CN), pyridine (C₅H₅N), and other organic bases present in small amounts but highly toxic.

Repeated exposure, even in small doses, could cause subtle organic changes, often unnoticed by the smoker. These discrete disturbances may indicate a progressive intoxication process with potential long-term consequences.

Héricourt (1904) notes that effects are most observed in the digestive and nervous systems. Upper respiratory tract irritation, persistent dry cough, and reduced appetite are typical. Moderate tobacco use may sometimes aid digestion, but excessive use impairs it and may provoke diarrhea.

Nervous system symptoms, termed nicotinism, include palpitations and memory impairment, particularly difficulty recalling proper names. Chronic intoxication may produce nausea, dizziness, vertigo, and gradual visual decline. Nicotine primarily affects nerve cells. Unlike alcohol, its effects are often reversible, resolving quickly after cessation. However, sudden symptoms could appear in smokers who maintained habits but changed environment – for instance, from outdoors to poorly ventilated indoor spaces – leading to intensified exposure.

Héricourt (1904) stated that the effects of nicotine and other products resulting from the incomplete combustion of tobacco primarily target nerve cells. However, unlike alcohol, this impregnation of the body tended to be less long-lasting. In many cases, simply ceasing tobacco consumption led to a relatively rapid disappearance of symptoms. There were, however, situations in which signs of intoxication appeared suddenly in smokers who had not altered their consumption habits. The author suggested that, in many circumstances, this phenomenon could be explained by changes in the environment in which tobacco was consumed. For example, individuals accustomed to smoking outdoors might begin to exhibit symptoms when smoking in enclosed, poorly ventilated spaces, such as small rooms or workplaces. Under such conditions, they would continuously inhale smoke-saturated air, which, in practice, amounted to a far more intense exposure to the toxic substances released during tobacco combustion.

Héricourt (1904) therefore considered that this situation also helped to explain why certain individuals continued to exhibit symptoms of nicotine intoxication even after they had ceased smoking. If they frequently remained in environments contaminated with second-hand tobacco smoke, or spent prolonged periods with smokers, they continued to be exposed to tobacco smoke and its harmful substances. For the same reason, attenuated forms of nicotinism could be observed in non-smokers, particularly women and children, whose sensitivity to tobacco was often greater. Some individuals displayed a particularly low tolerance to tobacco, as was the case with those of a nervous temperament or with certain organic predispositions (e.g., some patients with rheumatic conditions), tending to react more intensely to its effects.

Héricourt (1904) concluded this discussion on the interplay between the consumption of coffee and tobacco. Both substances were considered stimulants and were often used in combination, potentially exerting compensatory effects on one another to some extent. Thus, when a heavy smoker, who was also accustomed to consuming large quantities of coffee, suddenly reduced their intake-often believing it caused them discomfortsymptoms of nicotine intoxication that had previously been masked could immediately emerge. Similarly, abrupt cessation of tobacco could provoke manifestations associated with excessive caffeine intake. For this reason, the author did not recommend the reduction or elimination of stimulant in isolation. It would be prudent to advise moderation of both simultaneously, thereby avoiding the unexpected onset of disturbances related to their consumption.

3.5. Carbon Monoxide Poisoning

Prolonged exposure to carbon monoxide at the dawn of the twentieth century constituted a frequently underestimated hazard. This toxic gas could be present in a variety of everyday situations, particularly when certain heating or combustion systems were in use. Slow-combustion stoves, heaters, hot-air heating systems, coal or wood-fired stoves, as well as the domestic use of illuminating gas, were among the common systems of the time and potential sources of contamination. Furthermore, proximity to certain highly active industrial operations could contribute to increased levels of this gas in the urban environment.

Héricourt (1904) cautioned that, for a long time, public attention had been primarily focused on acute and fatal cases of carbon monoxide poisoning, often associated with domestic accidents. However, although such occurrences were relatively rare, there existed a potentially more insidious risk: continuous exposure to small quantities of this gas. In urban environments, such exposure could become habitual, gradually affecting the health of residents.

The chemist and pharmacist Ferdinand Frédéric Henri Moissan (1852-1907), the first French recipient of the Nobel Prize in Chemistry in 1906 (Tressaud, 2006) for his work isolating fluorine from its compounds (Nobel Foundation, 1966), was one of the researchers who, at the end of the nineteenth century, drew attention to this emerging problem-work with which Héricourt was familiar. Moissan warned of the dangers posed by small concentrations of carbon monoxide in the air of homes and cities. He emphasized that even extremely low amounts of this gas could provoke significant disturbances in the body, and that, moreover, the methods available at the time for its detection were largely ineffective. Thus, it was an almost invisible enemy, whose effects often escaped both human perception and medical diagnosis. Curiously, Moissan died suddenly in Paris on 20 February 1907, shortly after returning from the ceremony in Stockholm. Although the official cause was recorded as an acute appendicitis attack, some authors have suggested that prolonged exposure to toxic gases used in his experiments – particularly fluorine and carbon monoxide – may have contributed to the shortening of his life (Harrington, 1920).

Among the possible sources of poisoning, Héricourt (1904) highlights the domestic use of illuminating gas, which could contain between 7-10% carbon monoxide. Even a minor leak in a pipe, or the deterioration of a rubber hose, could release appreciable quantities of this gas into the air breathed within homes.

However, in his view, one of the main origins of the problem lay in modern heating systems. To produce more heat with lower fuel consumption, these devices began to carefully regulate the entry of air into combustion. This process, while energy-efficient, tended to promote the formation of higher amounts of carbon monoxide in the combustion gases. If the pipes or ducts carrying these gases were not perfectly sealed, carbon monoxide could easily infiltrate the air intended to heat the rooms of the house. In practice, it seems, the joints of these ducts were rarely executed with the necessary precision, often employing simple materials such as clay diluted in water, which, when heated, would shrink and quickly lose its effectiveness. Within a few days, fissures could form through which combustion gases escaped. Some appliances also incorporated cast-iron elements which, due to temperature variations, could crack relatively easily, further increasing the risk of leakage.

Mobile stoves and certain types of fireplaces posed even greater dangers. In these devices, the gases produced during combustion could contain particularly high proportions of carbon monoxide. Moreover, as the gases travelled up the chimney, they cooled rapidly, which reduced the draft and facilitated the return of gases into the room. Even a simple gust of wind could momentarily reverse the flow in the chimney, causing these gases to re-enter the domestic environment.

Even when valves or mechanisms intended to prevent such backflow were in place, these devices rarely ensured an effective seal for gaseous substances. On the contrary, their presence could create a false sense of security among users. Small leaks could occur repeatedly, contaminating the room air with hazardous amounts of carbon monoxide.

Therefore, many people using this type of equipment suffered, to a greater or lesser degree, the effects of chronic poisoning. It was already known that prolonged exposure to extremely low concentrations of this gas – like thousandths or even tenths of a thousandth in the air – was sufficient to produce health alterations.

The most common symptoms included headaches, often more intense towards the end of the day, dizziness, fainting spells, and neuralgias. In more severe cases, neurological disturbances could arise, such as paralysis or localized anesthesia in specific limbs or nerve paths. When exposure continued without recognition, the individual’s general condition tended to deteriorate progressively. Persistent anemia could develop, accompanied by easy fatigue and intolerance to physical exertion. Simple activities became tiring, walking caused rapid exhaustion, and loss of appetite and digestive disturbances frequently occurred. In some extreme cases, prolonged stay in contaminated environments could lead to profoundly serious consequences. For instance, people who worked for years in rooms heated by defective stoves, or who fell asleep near such appliances – sleepiness being one of the first signs of poisoning – could suffer severe neurological accidents, such as cerebral hemorrhages or rapid and profound mental alterations, even without any prior predisposition to such conditions.

Beyond domestic sources, there were also other origins of exposure in large cities. Intensive heating of homes during winter often created a layer of combustion gases over urban neighborhoods. Normally, these gases dispersed quickly into the atmosphere, but the situation became more concerning with industrial development.

The construction of large power plants intended for the production of energy, electricity, or motive power involved the continuous combustion of large quantities of fuel. These facilities released enormous volumes of smoke and gases into the atmosphere – including carbon dioxide, carbon monoxide, hydrogen sulphide (H₂S), and other harmful compounds – which spread across the surrounding areas. Under certain atmospheric conditions, these emissions could accumulate and infiltrate nearby streets and homes.

Thus, Héricourt (1904) considered it entirely plausible that many inhabitants of large cities were exposed, even if subtly, to the effects of chronic carbon monoxide poisoning. Even when symptoms were barely noticeable, such exposure could weaken the body’s resistance to various diseases. Some authors suggested that this reduction in vitality could, for example, facilitate the development of infectious diseases such as tuberculosis, the incidence of which remained high precisely during periods of intense urbanization and industrialization.

4. Conclusion

The present study has demonstrated that medical conceptions of so-called “initial intoxications”, formulated at the beginning of the twentieth century, were situated within a period of profound epistemological transformation in European medicine. Historical and documentary analysis revealed that the interpretation of intoxications caused by psychostimulants – such as alcohol, tobacco, tea, and coffee – and by carbon monoxide extended beyond the mere clinical description of symptoms, incorporating a broader understanding of the organism, physiological vulnerability, and the environmental and social conditions shaping health.

In the case of psychostimulants, there is a clear concern regarding the cumulative and chronic effects of excessive consumption, including neurological, digestive, and behavioral disturbances. Although the modern concept of dependence was not fully formulated at the time, symptomatic patterns are described that suggest mechanisms of tolerance and progressive deterioration, approximating notions now recognized as habituation phenomena and neurophysiological dysfunction. This historical reading demonstrates that many contemporary debates on consumption, risk, and regulation have deep conceptual roots predating the consolidation of modern pharmacology.

Regarding carbon monoxide, the study highlights the remarkable clinical and environmental foresight in recognizing slow and silent intoxications associated with domestic and urban contexts. The link between incomplete combustion, household heating, industrialization, and reduced bodily resilience anticipates central concerns of contemporary environmental toxicology. The notion that discrete and prolonged exposures could weaken the organism and predispose to the development of other pathologies aligns closely with current models integrating environment, chronic inflammation, and systemic vulnerability.

The study further shows that these medical reflections were situated at the intersection of experimental physiology, bacteriology, and emergent immunology. The shift from an exclusive focus on the pathogenic agent to an analysis of host responses represented a decisive change in understanding disease. In this context, research on immunity, serotherapy, and adverse reactions contributed to the construction of a more dynamic conceptual framework, in which organisms, environment, and external agents were understood as interdependent elements.

From a historiographical perspective, the research emphasizes the importance of revisiting scientific contributions that, though less celebrated, actively participated in the construction of the conceptual foundations of modern medicine. Contextualized analysis allows for the avoidance of anachronistic readings and provides insight into how categories such as “intoxication”, “vitality”, “resistance”, and “hygiene” functioned as explanatory devices in a period marked by rapid urbanization and technological transformation.

In terms of contribution to current scientific knowledge, this work underlines the relevance of integrating historical perspectives in the analysis of contemporary public health issues. Understanding continuities and discontinuities between past interpretations and current biomedical models supports a more critical approach to prevention policies, substance-use regulation, and environmental surveillance. Furthermore, it demonstrates that many present-day concerns – chronic exposure to invisible pollutants, the impact of socially accepted psychoactive substance use, and the interaction between environment and bodily vulnerability – have solid conceptual precedents that enrich contemporary scientific debate. The study confirms that historical analysis of medical ideas is not merely an exercise in reconstructing the past, but an epistemological tool relevant to understanding the genesis of fundamental concepts in public health, toxicology, and immunology, contributing to a more integrated and interdisciplinary view of the relationship between organism, environment, and society.