Pierre Charles Alexandre Louis

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Pierre Charles Alexandre Louis

Pierre Charles Alexandre Louis (14 April 1787 – 22 August 1872) was a French physician known for inventing the "numerical method", a precursor to modern clinical trials, and for his work on infectious diseases and bloodletting.


  • Between the one who counts the facts, grouped according to their resemblance, in order to know what to believe regarding the value of therapeutic agents and him who does not count but always says "more or less frequent," there is the difference between truth and error, between something that is clear and truly scientific and something that is vague and without value—for what place is there in Science for that which is vague?
    • Recherches sur les effets de la saignée dans quelques maladies inflammatoires, et sur l'action de l'émétique et des vésicatoires dans la pneumonie (1835) as quoted by William Coleman, Death is a Social Disease: Public Health and Political Economy in Early Industrial France (1982)
  • All [knowledge] comes from experience, it is true, but experience is nothing if it does not form collections of similar facts. Now, to make collections is to count.
    • Letter to Jean Cruveilhier (1837), as quoted by William Coleman, Death is a Social Disease: Public Health and Political Economy in Early Industrial France (1982)

Researches on the effects of bloodletting... (1836)[edit]

in some inflammatory diseases, and on the influence of tartarized antimony and vesication in pneumonitis
C. G. Putnam translation of Recherches sur les effets de la saignée... (1835)

  • From the exposition of facts... we infer that bloodletting has had very little influence on the progress of pneumonitis, of erysipelas of the face, and of angina tonsillaris, in the cases under my observation; that its influence has not been more evident in the cases bled copiously and repeatedly, than in those bled only once and to a small amount; that, we do not at once arrest inflammations, as is too often fondly imagined; that, in cases where appears to be otherwise, it is undoubtedly owing, either to an error in diagnosis, or to the fact that the bloodletting was practised at an advanced period of the disease, when it had nearly run its course; that, it would be well, nevertheless, in inflammations of imminent hazard, pneumonitis, for instance, to try whether a first bleeding sufficient to produce syncope, from twenty-five to thirty ounces or more, would not be attended with greater success; and finally that, wherever I have been able to compare the effect of general, with that of local bleeding by leeches, the superiority of the former has appeared to me demonstrated.
  • In any epidemic... let us suppose five hundred of the sick, taken indiscriminately, to be subjected to one kind of treatment, and five hundred others, taken in the same manner, to be treated in a different mode; if the mortality is greater among the first, than among the second, must we not conclude that the treatment was less appropriate, or less efficacious in the first class, than in the second ? It is unavoidable; for among so large a collection, similarities of condition will necessarily be met with, and all things being equal, except the treatment, the conclusion will be rigorous.
  • The objection made to the numerical method, to wit, the difficulty or impossibility of forming classes of similar facts, is alike applicable to all the methods that might be substituted; that it is impossible to appreciate each case with mathematical exactness, and it is precisely on this account that enumeration becomes necessary; by so doing, the errors, (which are inevitable,) being the same in two groups of patients subjected to different treatment, mutually compensate each other, and they may be disregarded without sensibly affecting the exactness of the results.

Quotes about Louis[edit]

  • Pierre Charles Alexandre Louis should be honored as a primary author of the "numerical method." By "numerical method" he meant that the stages of disease and therapeutic outcomes should be expressed in terms of numbers and not merely as a set of verbal descriptions. ...This method seems so sensible that it is difficult to see why it was resisted by the medical establishment.
    • I. Bernard Cohen, The Triumph of Numbers: How Counting Shaped Modern Life (2005)
  • By the middle of the 1830s the numerical method, which Louis enshrined as the doctrinal heart of his new Société médicale d'observation, had become probably the most fiercely contested proposition in all of French medicine.
    • William Coleman, Death is a Social Disease: Public Health and Political Economy in Early Industrial France (1982)
  • [John P.] Bull... wrote his history of the clinical trial in 1951. He argued that the conduct of "clinical trials" can be traced to the ancient Egyptians. ...Highlighting historic events—such as Avicenna's rules for testing drugs, Francis Bacon's suggestion of a committee of physicians to judge therapeutic efficacy, James Lind's comparative trial of scurvy "cures", and P.C.A. Louis's application of his numerical method in the clinic—Bull presents a linear account of the development of the clinical trial. The implication... is that, cumulatively, these historic experiments made the clinical trial progressively more scientific.
    • Arne Hessenbruch, Reader's Guide to the History of Science (2013)
  • P. Ch. A. Louis, physician of the Hospital de la Pitié, is a man, whose labors and whose writings must become more and more known for ages. I should deem it service enough to my brethren in this country, if I could induce them, one and all, to read and study the works of this great pathologist. M. Louis is the founder of the numerical system, as it has been denominated, in respect to the science of medicine. ...M. Louis has not brought forward a new system of medicine; he has only proposed and pursued a new method in prosecuting the study of medicine. This is nothing else than the method of induction, the method of Bacon, so much vaunted and yet so little regarded.
    ...To estimate the value of his observations, it is necessary to understand the plan, on which he collected them. First, then, he ascertained when the patient under his examination began to be diseased. Not satisfied with vague answers, he went back to the period, when the patient enjoyed his usual health; and he also endeavored to learn whether that usual health had been firm, or in any respect infirm. He noted also the age, occupation, residence, and manner of living of the patient; likewise any accidents which had occurred, and which might have influenced the disease then affecting him. He ascertained also, as much as possible, the diseases which had occurred in the family of his patient. Secondly, he inquired into the present disease, ascertaining not only what symptoms had marked its commencement, but those which had been subsequently developed and the order of their occurrence; and recording those, which might not seem to be connected with the principal disease, as well as those which were so connected; also, measuring the degree or violence of each symptom, with as much accuracy as the case would admit. Thirdly, he noted the actual phenomena present at his examination, depending for this not only on the statement of the patient, but on his own senses, his eyes, his ears and his hands. Under this and the preceding head he was not satisfied with noting the functions, in which the patient complained of disorder, but examined carefully as to all the functions, recording their state as being healthy or otherwise, and even noticing the absence of symptoms, which might bear on the diagnosis. Thus all secondary diseases, and those, which accidentally co-existed with the principal malady, were brought under his view. Fourthly, he continued to watch his patient from day to day, carefully recording all the changes, which occurred in him till his restoration to health, or his decease. Fifthly, in the fatal cases he exercised the same scrupulous care in examining the dead, as he had in regard to the living subject. Prepared by a minute acquaintance with anatomy, and familiar with the changes wrought by disease, he looked not only at the parts where the principal disorder was manifested, but at all the organs. His notes did not state opinions, but facts. He recorded in regard to each part, which was not quite healthy in its appearance, the changes in color, consistence, firmness, thickness, &c.; not contenting himself with saying that a part was inflamed, or was cancerous, or with the use of any general, but indefinite terms.
  • He studies nature with a full faith in the uniformity of her laws, and in the certainty that truth may be ascertained by diligent labor. It is truth only he loves; not anxious to build up a system, nor pretending to explain every thing, he says to his pupils, such and such have been my observations; you can observe as well as I, if you will study the art of observation, and if you will come to it with an honest mind, and be faithful in noting all which you discover, and not merely the things which are interesting at the moment, or those which support a favorite dogma; I state to you the laws of nature as they appear to me; if true, your observations will confirm them; if not true, they will refute them; I shall be content if only the truth be ascertained.
    • James Jackson, Preface, Researches on the effects of bloodletting... (1836)
  • My sole expectation is to lead some, who might otherwise be ignorant of them, among my brethren of the present day, to study works which I esteem as among the most valuable certainly, if not the most valuable, which any age has furnished us in regard to medicine. ...these principles may be added to, they may be enlarged, limited and modified, and yet the system may be maintained; and it will still derive its support from the first labors devoted to its erection as much as from the last.
    • James Jackson, Preface, Researches on the effects of bloodletting... (1836)

External links[edit]