In modern Western medicine, the conventional way of acquiring medical knowledge about the body involves the telling and retelling of patients' stories (the history), and the gathering of physical evidence, both immediate (the examination) and hidden (the further investigations). From this information, patients' conditions are given names (the diagnosis) or, if their doctors cannot be specific, several possible names (the differential diagnosis). Armed with a diagnosis, doctors can inform their patients about what will happen to them (the prognosis), and begin treatment.
HistoryEven in the age of high technology medicine, nothing improves the efficiency and efficacy of medical intervention more than an accurate and complete history, detailing a patient's medical problems, past and present, their family's medical history, and their social circumstances. Histories, however extended and refined, have been an integral part of Western medicine for 2500 years. The works ascribed to the Greek physician Hippocrates (sc. 460–370 bc) notably include the Epidemics, in which the author notes details of patients' circumstances before and during their illness, as well as the presence and nature of any change in their condition, mental or physical. These works may have been little more than an aide-memoire for the author in his practice, or possibly in his teaching, but, as the author of the first book of Epidemics describes, ‘learning from the common nature of all and the particular nature of the individual, from the disease, the patient, the regimen prescribed and the prescriber’ allowed him to make more accurate judgements about the likely outcome of the case. Case histories are written repositories of the collective experience of the medical profession.
The ultimate purpose of the history is to understand the patient, their environment, and their place in society. At various times in history it has been considered important to know where patients live (Hippocratic doctors believed that each locality was prone to particular diseases because of its climate); when they were born (Arabic and medieval Western medicine placed much emphasis on the astrological portents accompanying illness); or what their job is (many occupational diseases have been identified since the English surgeon Percival Pott (1714–88) first described cancer of the scrotum in chimney sweeps).
Besides being good listeners, doctors are also natural storytellers. Recent scholarship by physicians, literary critics, and anthropolgists has drawn attention to the narrative structure of medical knowledge, in particular how patients' endlessly varied and complex ‘stories of sickness’ are translated into more strictly regimented ‘doctors’ stories'. Medical students are taught to ask specific questions in order to elicit information for all the categories of the ideal case history: the presenting complaint, the history of that complaint, the patient's past medical history, their past medications and allergies, their family history, and their social circumstances (including their smoking and drinking habits). They are taught to interpret patients' symptoms and organize them into systems — cardiovascular, respiratory, gastrointestinal, nervous, and so on. As critics of medicine have pointed out, the resulting narrative bears little resemblance to that presented by the patient, and there is a danger that the story may lose something — the patient as an individual — in translation if the doctor is not alive to that possibility. The taking of accurate and full histories is vital for the science of medicine; the art of medicine is to construct, within the bounds of accepted form, a vibrant history which retains the concerns and character of the patient while stressing those aspects of the illness which are amenable to medical intervention.
ExaminationClinical examination of patients' bodies creates, not least by the symbolism of laying on of hands, a special relationship between doctors and their patients. Clinical examination, like history-taking, has a long history. The author of the Epidemics, for example, paid as much attention to the physical state of his patients' bodies as to the symptoms of which they complained. He regularly noted the presence of fever, jaundice, or enlargement of the spleen, and the character of any sputum, urine, and faeces. Many other Hippocratic texts record physical findings, such as the sweet taste of diabetic urine. Indeed, Hippocratic medicine was based around semiotics — the recognition and interpretation of signs — and it is startling to realize that these skills were for the most part held in abeyance by the medical profession for over 2000 years, until the creation of clinical medicine in the late eighteenth century. Social mores conspired to keep doctors away from the body, though such taboos did not apply to substances excreted from it. While the doctor would often be limited in his examination to feeling the patient's pulse, he usually had free access to the urine, faeces, and other excreted matter. The interpretation of pulses and urines became highly refined skills: Chinese doctors, for example, used a silk thread held between the thumb and forefinger to feel the oscillations of six pulses in the wrist, each one of which was thought to correspond to a specific internal organ; medieval Western doctors carried specially designed urine bottles, and charts showing the colours and character of morbid urines.
At the end of the eighteenth century a new form of medicine was created in European hospitals. Clinical medicine required immediate access to patients' bodies, both in life and after death, in order to elicit signs of disease and to correlate those signs with morbid changes seen post mortem. The egalitarian hospitals of Paris, crowded with soldiers returned from the Napoleonic wars, proved an ideal environment in which this new approach to the body could flourish. Old, rarely used skills, such as percussion (first described in the 1730s by the Austrian physician Leopald Auenbrugger (1722–1809), were rediscovered and refined. New skills were introduced, most notably auscultation of patients' hearts and lungs by means of the stethoscope, an instrument which has become emblematic of modern medicine. The stethoscope signifies both doctors' intimacy with, and their detachment from, their patients' bodies: immediate auscultation — putting one's ear directly to the patient's chest — was often physically unpleasant or socially unacceptable. Mediate auscultation (listening to the chest through a tube), invented by the French physician René-Théophile-Hyacinthe Laënnec (1781–1826) in 1816, spared the sensibilities of both doctors and their patients, as well as improving the acoustics of the technique.
Modern doctors are heir to the spirit as well as the skills of the first clinicians. Medical students learn, and repeatedly practice, the four central skills: inspection, palpation, percussion, and auscultation. The spirit of clinical examination was captured by the English surgeon George Humphry (1821–96) in the aphorism ‘eyes first and most, hands next and little, tongue not at all’. Of these perhaps the most important is the first. Few diseases produce pathognomonic signs — the ‘spot diagnosis’ beloved of senior students and junior doctors — but experienced clinicians can sometimes determine much of what they need to know about their patients' health simply by observing them carefully. Arthur Conan Doyle (1859–1930) modelled his fictional detective Sherlock Holmes, the epitome of skilled observation, on the Edinburgh physician Joseph Bell (1837–1911), a doctor of tremendous clinical acumen who insisted that successful diagnosis was due to the ‘precise and intelligent recognition and appreciation of minor differences’.
InvestigationsClinical medicine, created at the end of the eighteenth century, enjoyed a golden age in the flourishing hospitals of the nineteenth century. Yet doctors still had to cope with the unyielding complexity and variability of the human body, and the fundamental uncertainty of medical practice. In their quest for certainty, doctors in Europe and the US turned to science for answers. Science itself was a new, fragile discipline at this time: experimental physiology, pathology, and pharmacology first flourished in Berlin and Paris in the 1820s. As scientists delved ever deeper into the anatomy and physiology of the human body, they devised new methods of investigation, which soon entered medical practice. Chemical tests for the presence of sugar or protein in urine, supplanting previous methods such as close inspection or tasting, entered practice in the 1840s and 1850s, at a time when the chemical study of biological processes was being pioneered by the German chemist Justus Liebig (1803–73). The investigation of blood and other tissues under the microscope became necessary in the context of the cell theory, first propounded in 1838 by the German physiologist Theodor Schwann (1810–82) but vastly extended and modified by the German pathologist Rudolf Virchow (1821–1902). With the advent of the germ theories of disease — created and implemented by the French chemist Louis Pasteur (1822–95) and the German bacteriologist Robert Koch (1843–1910) — finding, fixing, and staining bacteria became part of standard medical practice. By 1914, public institutions and private companies were providing extensive diagnostic laboratory services for doctors throughout Europe and the US.
The discovery of X-rays, in 1895, by the German physicist Wilhelm Röntgen (1845–1923), was immediately exploited by the medical profession to examine areas of the human body which were previously inaccessible in life. X-rays proved especially useful in diagnosing fractures and chest diseases. Since World War II several new imaging techniques have been developed: ultrasound began to be used to diagnose diseases of the brain, heart, and abdomen in the 1950s; computerized axial tomography (the CAT scan, now known simply as computed tomography, or CT), invented by the British electrical engineer Godfrey Hounsfield (1919– ), was introduced commercially into practice in 1972; more recently still, magnetic resonance imaging (MRI) and positron emission topography (PET) technology are providing detailed information about the anatomy and physiology of the body.
Imaging technology primarily provides information about the structure of the body. Information about its function comes from other investigations, the earliest and most widely used of which is the electrocardiograph (ECG), which records the electrical activity of the heart. The ECG was first described in 1903 by the Dutch physiologist Willem Einthoven (1860–1927). Similar technology was applied to the recording of brain waves when in the 1930s the American physicist Alfred Loomis (1887–1975) and his colleagues showed that electroencephalograph (EEG) recordings varied during a night's sleep.
Patients entering hospital today, for whatever reason, can expect to have blood taken for simple tests, their ECG recorded, and a chest X-ray taken. Those with suggestive findings in their histories or examinations may then have more complex investigations undertaken. In many cases these investigations will allow a firm diagnosis to be made; in others they may simply confirm a diagnosis already arrived at by clinical reasoning, while giving some indication of the prognosis of the individual patient's illness; in yet others they may provide little or no information to confirm or rule out a diagnosis. Despite the enormous incursion of science into medicine over the last two hundred years, medicine remains an enterprise best characterized by the Hippocratic aphorism, ‘Life is short, the art long, opportunity fleeting, experience treacherous, judgement difficult’.
Diagnosis, prognosis, and therapyAnd what do doctors do when they have taken their patient's history, examined them, and made all the necessary investigations? In modern medicine the goal of all these activities is the making of a diagnosis and, ideally, the implementation of therapy. Diagnosis is so central to modern medicine that it is difficult to believe that in earlier eras it could be a matter of little or no interest. The goal of Hippocratic medicine, for example, was to establish the patient's prognosis, that is, the likely future course and outcome of their illness given their past course and present state. Prognosis was important for the Hippocratic doctor, partly because he would only take on cases that he thought would recover (his reputation and even his life being in danger if his patient died), and partly because he had little to offer his patients in the way of specific treatment for disease, believing that diseases arose from an imbalance within the body, or between the body and its environment. Very occasionally some surgical manipulation was indicated, usually to replace a dislocated or broken bone, but otherwise Hippocratic therapy required a change of regimen (in modern terms, lifestyle, including food, drink, and exercise, both physical and mental) to restore the lost equilibrium.
In those cases which Hippocratic doctors did take on, the goal of therapy was to cure the patient completely. This remained the sole goal of therapeutics until the late eighteenth and early nineteenth centuries. Specifics — single drugs which cured specific diseases, hence their name — were highly valued and very rare. As doctors, and in many cases their patients, became increasingly sceptical about the value of long-used remedies, new schools of thought both within and outside the medical establishment began to preach that nature alone cured disease, and that doctors could at best hope to treat the patient by promoting and aiding nature's best efforts. Within orthodox medicine this sceptical attitude fostered experimental research into the actions of drugs: in the 1820s, for example, the French physiologist François Magendie (1783–1855) and pharmacist Pierre-Joseph Pelletier (1788–1842) isolated strychnine from nux vomica, morphine from opium, and quinine from Peruvian bark; around 1900 the German pharmacologist Paul Ehrlich (1854–1915) investigated hundreds of chemicals in his search for antimicrobial agents, before the 606th (christened ‘Salvarsan’) proved to be effective against the spirochaete that caused syphilis; and in 1941, the Australian pathologist Howard Florey (1898–1968) and the British biochemist Ernst Chain (1906–79) purified penicillin from the Penicillium mould first described in 1928 by the British physician Alexander Fleming (1881–1955). Today, new drugs are evaluated in thousands of patients at dozens of hospitals, the results of trials being subjected to sophisticated statistical analysis on powerful computers. Armed with these results, however, an individual physician must still decide whether they apply to each individual patient; often a policy of watching and waiting, without giving drugs may be the most appropriate. Outside orthodox medicine a natural scepticism reached its acme in the doctrine of homœopathy, invented by the German physician Samuel Hahnemann (1755–1843), according to which diseases are treated with drugs at infinitesimal dilutions.
surgery — which prior to the nineteenth century had hardly been regarded as part of medicine at all (in mediaeval times surgeons shared their guild, and their work, with barbers) — flourished as pills and potions fell out of favour. The development of anaesthesia by the American dentists William Morton (1819–68) and Horace Wells (1815–48), and its rapid uptake by surgeons across the world, revolutionized surgical practice, allowing longer and more complex operations to be carried out. This however was of little importance if the majority of those operated upon died of infection soon afterwards; the introduction of antiseptic technique by the Scottish surgeon Joseph Lister (1827–1912), and the subsequent development of aseptic operating theatres, was of equal importance in raising the prestige and effectiveness of surgical treatment of disease. By providing a scientific basis for personal hygiene, these developments also transformed preventive medicine by adding new weapons to its previous armoury of quarantine and sewers.
The contributions of scientific research to medicine in the twentieth century were legion, but scientific progress has often brought with it new ethical, social, and financial dilemmas for medicine. In cardiology, for example, the development of basic and advanced life support techniques, and of new drugs designed to prevent and treat heart disease, have significantly reduced the chances of dying from a heart attack. But the cost of the equipment needed for advanced life support, and of drugs (such as those that lower cholesterol in the blood) that improve survival, mean that these therapies are largely confined to well-funded hospitals in wealthy countries. Again, one of the most significant discoveries of all occurred in 1921 when the Canadian physiologists Frederick Banting (1891–1941) and Charles Best (1899–1978) isolated the hormone insulin. At last it seemed that there would be a cure for diabetes mellitus, a disease recognized since Hippocratic times. But seventy-five years of experience with insulin has taught us that it does not cure the disease. The pancreatic b-cells whose destruction is the defining stage in the disease are not restored by giving insulin. Instead, insulin allows diabetes to be managed, a difficult, time-consuming, often frustrating process that requires doctors and their patients to co-operate over long periods. Nothing could demonstrate the difference between the science and the art of medicine more clearly: scientists push on, trying to understand the pathological processes that take place in the body of a patient with diabetes, elucidating the genetics of both common and rare forms of the disease, and producing new therapies such as recombinant human insulin; doctors, meanwhile, continue to wrestle, as their ancestors did for thousands of years, with the complexity, variability, and uncertainty of their patients' bodies, and their patients' minds.
D. J. Weatherall
See also diagnosis; disease.
(b. Semarang, Java, 21 May 1860; d. Leiden, Netherlands, 28 September 1927)
Einthoven’s father was municipal physician of Semarang; he married Louise M. M. C. de Vogel. He died in 1866, and four years later his widow settled in Utrecht with their six children. There Willem Einthoven graduated from high school and registered as a medical student in 1879. In 1886 he married his cousin Frédérique Jeanne Louise de Vogel; they had three daughters and a son.
While a student, Einthoven was active in sports; when he broke his wrist in a fall, he made it the occasion to publish a study on the pronation and supination of the forearm (1882). On 4 July 1885 he received the Ph.D in medicine cum laude with a thesis on stereoscopy through color differentiation. The following December he was appointed professor of physiology at Leiden.
In 1895, after the London physiologist A. D. Waller had published the curve for the action current of the heart as deduced from the body surface and had announced that he was unable to calculate its true shape (as recorded with Lippmann’s capillary electrometer), Einthoven repeated this experiment. He defined the physical constants of the capillary electrometer and calculated the true curve, which he called the electrocardiogram. Einthoven considered direct registration of the curve’s true curve, which he called the electrocardiogram. Einthoven considered direct registration of the curve’s true shape a necessity. Starting from the mirror galvanometer of Deprez-d’ Arsonval, he arrived at his brilliant conception of the string galvanometer. In 1896, while working on the construction of this instrument and developing the necessary photographic equipment, he registered electrocardiograms with the capillary electrometer as well as heart sounds of humans and animals.
For making electrocardiograms Einthoven chose the ordinate and abscissa in such a way that all details of the electrocardiogram would appear as clearly as possible. In 1903 he defined the standard measures for general use—one centimeter movement of the ordinate for one millivolt tension difference and a shutter speed of twenty-five millimeters per second, so that one centimeter of the abscissa represented 0.4 second. He indicated the various extremes by the random letters P, Q, R, S, and T and chose both hands and the left foot as contact points. This gave three possible combinations for contact which he labeled I (both hands); II (right hand-left foot); and III (left hand-left foot).
In 1912 Einthoven’s research on the explanation of the respiratory changes in the electrocardiogram led him to the scheme of the equilateral triangle, considering the extremities as elongations of the electrodes. The information received from the contacts thus represents the projection of what takes place in the heart. With simultaneous registration of the three contacts, the size and direction of the resultant of all potential differences in the heart could be calculated minute by minute. Einthoven referred to this as the manifest size and direction of the electrical axis. He indicated the direction by the angle α of the axis with the horizontal and called it positive when it turned clockwise, negative when counterclockwise. Clinical electrocardiograms were studied by connecting patients with heart disease in the academic hospital to the instrument in Einthoven’s laboratory by means of a cable 1.5 kilometers long (1906).
These “telecardiograms” acquainted Einthoven with many forms of heart disease. In addition he deepened his insight by registering heart sounds and murmurs simultaneous to the electrocardiogram by means of a second string galvanometer. The construction of a string recorder and a string myograph, both based on the torsion principle, enabled him to prove that the electrocardiogram and muscle contraction are inseparably connected.
While visiting America to give the Dungham lectures (1924) Einthoven was awarded the Nobel Prize for physiology or medicine. Upon his return to Leiden he found two foreign requests to register the action currents of the cervical sympathetic nerve. With the newly constructed vacuum string galvanometer he succeeded, on 28 April 1926, in registering the tonus action current and, after irritation of the organ, the thereupon induced action current of the cervical sympathetic nerve. His last major physical experiment, which he carried out in company with his son, was concerned with the reception of radiotelegrams broadcast by the machine transmitter “Malabar” in Java. In this case the string of 0.1 micron diameter and six millimeters length and to be synchronized with the 40,000 vibrations of the transmitting wave. Einthoven and his son found the resonance point after they achieved a variation in tension of one micro micron, after which telegrams from the machine transmitter, working at top speed, were perfectly photographed on paper one centimeter wide.
Einthoven’s last work was his treatise on the action current of the heart, which appeared posthumously in Bethe’ Handbuch der normalen und pathologischen Physiologie.
I. Original Works. Einthoven’s works include “Quelques remarques sur le mécanisme de l’articulation du coude”, in Archives nėerlandaises des sciences exactes et naturelles, 17 (1882), 289–298; “Stéréscopie dépendant d’une différence de couleur”, ibid., 20 (1886), 361–387; “Lippmann’s Capillarelektrometer zur Messung schnell wechseln der Potentialunterschiede”, in Pflügers Archiv für die gesamte physiologie des Menschen und der Tiere, 26 (1894), 528–540; “Die Registrierung der Herztöne”, ibid., 57 (1894), 617–639, written with M. A. J. Geluk; “Über den Einflusz des Leitungswiderstandes auf die Geschwindigkeit der Quecksilberbewegungen in Lippmann’s Capillarelektrometer”, ibid., 60 (1895), 91–100; “Über die Form des menschlichen Elektrocardiogramms”, ibid,. 101–123; “Beitrag zur Theorie des Capillarelektrometers”, ibid., 79 (1900), 1–25; “Eine Vorrichtung zum Registrieren der Ausschlage des Lippmann’schen Capillarelektrometers”, ibid., 25–38; “Über das normale menschliche Elektrokardiogramm und die capillarelektrometrische Untersuchung einiger Herzkranken”, ibid,. 80 (1900), 139–160, written with K. de Lint; “Un nouveau galvanométre” in Archives néerlandaises des sciences exactes et naturelles, 6 (1901), 625–633; “Die galvanometrische Registrierung des menschlichen Elektrokardiogramms, zugleich eine Beurteilung der Anwendung des Capillarelektrometers in der Physiologie”, in Pflügers Archiv für die gesamte physiologie des Menschen und der Tiere, 99 (1903), 472–480.
See also “Über einige Anwendungen des Saitengalvanometers”, in Annalen der Physik, 14 (1904), 182–191; “Über eine neue Methode zur Dämpfung oszillierender Galvanometerausschlage,” ibid., 16 (1904), 20–32; “Weitere Mitteiloungen Uber das Saitengalvanometer. Analyse der saitengalvanometrischen Kurven. Masse und Spannug des Quarzfadens und Widerstand gegen die Fadenbewegung”, ibid., 21 (1906), 483–514, 665–701; “Le télécardiogramme”, in Archives Internationaldes de Physiologie, 4 (1906), 132–165; “Die Registrierung der menschlichen Herztöne mittels des Saitengalvanometers”, in Pflugers Archiv für die gesamte Physiologie des Menschen und der Tierre, 117 (1907), 461–472, written with A. Flohil and P. J. J. A. Battaerd; “Ein dritter Herzton”, ibid., 120 (1907), 31–43, written with J. H. Wieringa and E. P. Snijders; “Weiteres öber das Elektrokardiogramm”, ibid., 122 (1908), 517–585, Written with B. Vaandrager; “Die Konstruktion des Saitengalvanometers”, ibid.,130 (1909), 287–321; “Über die Deutung des Elektrokardiogramms,” ibid149 (1913), 65–86, “Eine Vorrichtung zur photographischen Registrierung der Zeit,” in Zeitschrift für biologische Technik und Methodik, 3 (1912),1–8; and “Über die Richtung und die manifeste Grösse der Potentialschwankungen im menschlichen Herzen und über den Einfluss der Herzlage auf die Form des Elektrokardiogramms,” in Pflügers Archiv für die gesamte Physiologie des Menschen und der Tierre, 150 (1913), 275–315, written with G. Fahr and A. de Waart.
Subsequent works are “On the Variability of the Size of the Pulse in Cases of Auricular Fibrillation,” in Heart, 6 (1915), 107–121, written with A.J. Korteweg; “Die gleichzeitige Registrierung elektrischer Erscheinungen mittels zwei oder mehr Galvanometer und ihre Anwendung auf die Elektrokardiographie,” in Pflügers Archiv fürdie gesamte Physiologie des Menschen und der Tiere, 164 (1916), 167–198, written with L. Bergansius and J. Bijtel; and “Über den Zusammenhang zwischen Elektro-und Mechanodardiogramm,” in Berichte über die gesamte Physiologie und experimentelle Pharmakologie, 2 (1920), 178.
His last works include “L’électrocardiogramme tracé dans le cas où il n’y a pas de contraction visible du coeur,” in Archives néerlandaises de physiologie de l’homme et des animaux, 5 (1921), 174–183, written with F. W. N. Hugenholtz; “Über die Beobachtung und Abbildung dönner Faden,” in Pflügers Archiv für die gesamte Physiologie des Menschen und der Tiere, 191 (1921), 60–98; “Über Stromleitung durch den menschilchen Körper,” ibid., 198 (1923), 439–483, written with J. Bijtel; “Functions of the Cervical Sympathetic Manifested by Its Action Currents,” in American Journal of Physiology, 65 (1923), 350–362, written with Joseph Byrne; “The Relation of Mechanical and Electrical Phenomena of Muscular Contraction, With Special Reference to the Cardiac Muscle,” in The Harvey Society Lectures (Philadelphia-London, 1924–1925), pp. 111–131; “Das Saitengalvanometer und die Messung der Aktionsströme des Herzens,” in Les Prix Nobel 1924–1925 (Stockholm, 1926), p. 18, his Nobel Prize acceptance speech; “Gehirn und Sympathicus, die Aktionsstrome des Hallsympathicus,” in Pflügers Archiv für die gesamte Physiologie des Menschen und der Tiere, 215 (1927), 443–453, written with S. Hoogerwerf, J. P. Karplus, and A. Kreidl; and “Die Aktionsstrome des Herzens,” in Bethe’s Handbuch der normalen und pathologischen Physiologie, 8 (1928), 785–862.
II. Secondary Literature. On Einthoven and his work see S. L. Barron, Willem Einthoven, Biographical Notes, Cambridge Monograph no. 5 (London, 1952), pp. 1–26; F.L. Bergansius, “Willem Einthoven,” in Wetenschappelijke bladen, 1 (1925), 257; A. V. Hill, “Obituary. Prof. W. Einthoven,” in Nature, 120 (1927), 591–592; Leonard Hill, “Willem Einthoven;” in British Medical Journal (1927), 2 , 665; S. Hoogerwerf, Leven en Werken van Willem Einthoven (Hoorn, 1925), 9–93; and “Willem Einthoven,” in T. P. Sevensma, ed., Nederlandsche Helden der Wetenschap (Amsterdam, 1946), 239–297; J. E. Johansson, “W. Einthoven (1924–1925),” in Les Prix Nobel Nobel 1924–1925 (Stockholm, 1926); C.L. de Jongh, “Het levenswerk van Einthoven,” in Nederlandsh tijdschrift voor geneeskunde, 98 (1954), 270–273; T. Lewis, “Willem Einthoven,” in British Medical Journal (1927), 2 664–665; G. van Rijnberk, “Willem Einthoven,” in Nederlandsch tijdschrift voor geneeskunde, 68 (1924), 2424–2430; “In Memoriam,” ibid., 71 (1927), 1502–1503; E. Schott, “Willem Einthoven und die Fortschritte, welche wir der Erfindung des Saitengalvanometers verdanken,” in Münchener medzinische Wochenschrift, 72 (1925), 391–392; A. Sikkel, “In Memoriam W. Einthoven,” in Geneeskundige gids, 5 (1927), 925; “Nectologie Einthoven,” in University of Leiden, Jaarboek, 1928; A. de Waart, Einthoven (Haarlem, 1957), with a complete list of his works; K. F. Wenckebach, “W. Eionthoven,” in Deutsche medizinische Wochenschrift, 51 (1927), 2176; F. A. F. C. Went, “Herdenkingsrede,” in Verslagen van de gewone vergadering van de Koninklijke Nederlandsche Academie van Wetenschappen. Afdeling Natuurkunde, 8 (1927), 936–938; and H. Winterberg, “W. Einthoven,” in Wiener klinische Wochenschrift, 40 (1927), 1460–1461.