Jacques Loeb

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Jacques Loeb
Jacques Loeb.jpg
BornApril 7, 1859
DiedFebruary 11, 1924(1924-02-11) (aged 64)
ChildrenLeonard Benedict Loeb
Scientific career
FieldsPhysiology, Biology

Jacques Loeb (/lb/;[1] German: [løːp]; April 7, 1859 – February 11, 1924) was a German-born American physiologist and biologist.


Jacques Loeb, firstborn son of a Jewish family from the German Eifel region, was educated at the universities of Berlin, Munich, and Strasburg (M.D. 1884). He took postgraduate courses at the universities of Strasburg and Berlin, and in 1886 became assistant at the physiological institute of the University of Würzburg, remaining there till 1888. In a similar capacity, he then went to Strasburg University. During his vacations he pursued biological researches, at Kiel in 1888, and at Naples in 1889 and 1890.

Jacques Loeb first arrived in the United States in 1891 when he accepted a position at Bryn Mawr College, however, they provided insufficient facilities for his work which would later influence his resignation.[2] In 1892, he was called to the University of Chicago as assistant professor of physiology and experimental biology, while later becoming associate professor in 1895, and professor of physiology in 1899. John B. Watson (the "father of Behaviorism") attended Loeb's neurology classes at the University of Chicago.[3] He was elected as a member to the American Philosophical Society in 1899.[4] In 1902, he was called to fill a similar chair at the University of California.

In 1910, Loeb moved to the Rockefeller Institute for Medical Research in New York, where he headed a department created for him. He remained at Rockefeller (now Rockefeller University) until his death. Throughout his career, Loeb spent some summers at the Marine Biological Laboratory in Woods Hole, Massachusetts, performing experiments on various marine invertebrates. While there, Jacques Loeb performed his most famous experiment, on artificial parthenogenesis. With this experiment, Loeb was able to cause the sea urchins' eggs to begin embryonic development without sperm. The slight chemical modifications of the water in which the eggs were kept, served as the stimulus for the development to begin.[5][6] Later in 1918, Loeb established and became the first Editor of the Journal of General Physiology.

Jacques Loeb became one of the most famous scientists in America, widely covered in newspapers and magazines, influencing other important individuals in the scientific world such as B.F. Skinner.[7] He was the model for the character of Max Gottlieb in Sinclair Lewis's Pulitzer-winning novel Arrowsmith, the first great work of fiction to idealize and idolize pure science.[8] Mark Twain also wrote an essay titled "Dr. Loeb's Incredible Discovery", urging the reader not to support a rigid general consensus, but to instead be open to new scientific advances.[9]

Loeb was nominated many times for the Nobel Prize but never won.

Loeb was an atheist.[10][11]

Research area[edit]

The main subjects of Loeb's work were:

  • Animal tropisms and their relation to the instincts of animals
  • Heteromorphosis, the replacement of an injured or removed organ by a different organ
  • Toxic and antitoxic effects of ions
  • Artificial parthenogenesis
  • Hybridization of the eggs of sea-urchins by the sperm of starfish


Among Loeb's works the following may be mentioned:

  • Der Heliotropismus der Thiere und seine Uebereinstimmung mit dem Heliotropismus der Pflanzen, Würzburg: Verlag von Georg Hertz, 1890.
  • Untersuchungen zur physiologischen Morphologie der Thiere, Würzburg: Verlag von Georg Hertz, 1891–1892. 2 vols., vol. 1: Ueber Heteromorphose, vol. 2: Organbildung und Wachsthum.
  • Einleitung in die vergleichende Gehirnphysiologie und vergleichende Psychologie, Leipzig: J. A. Barth, 1899. English ed., Comparative physiology of the brain and comparative psychology, New York: Putnam, 1900.
  • Studies in general physiology, Chicago: The University of Chicago Press, 1905.
  • The dynamics of living matter, New York: Columbia University Press, 1906.
  • The mechanistic conception of life: biological essays, Chicago: The University of Chicago Press, 1912; reprint, Cambridge, Mass.: Harvard University Press, 1964.
  • Artificial parthenogenesis and fertilization, tr. from German by W. O. Redman King, rev. and ed. by Loeb. Chicago: The University of Chicago Press, 1913.
  • The organism as a whole, from a physicochemical viewpoint, New York: Putnam, 1916.
  • Forced movements, tropisms, and animal conduct, Philadelphia: Lippincott, 1918.
  • Proteins and the theory of colloidal behavior, New York: McGraw-Hill, 1922.

The Mechanistic Conception of Life is Loeb's most famous and influential work. It contains English translations of some of his previous publications in German.


His younger brother Leo also emigrated to the United States where he became a noted pathologist.


  1. ^ "Loeb". Random House Webster's Unabridged Dictionary.
  2. ^ Osterhout, W. J. V. (1928-09-15). "JACQUES LOEB". The Journal of General Physiology. 8 (1): IX–LVIII. doi:10.1085/jgp.8.1.ix. ISSN 0022-1295. PMC 2140786. PMID 19872180.
  3. ^ Introduction to: "Psychology as the Behaviorist Views it."
  4. ^ "APS Member History". search.amphilsoc.org. Retrieved 2021-04-20.
  5. ^ Loeb, J (1914), "Activation of the Unfertilized Egg by Ultra-Violet Rays", Science (published Nov 6, 1914), 40 (1036), pp. 680–681, Bibcode:1914Sci....40..680L, doi:10.1126/science.40.1036.680, PMID 17742992
  6. ^ Ball, Philip (2016). "Man Made: A History of Synthetic Life". Distillations. 2 (1): 15–23. Retrieved 22 March 2018. CS1 maint: discouraged parameter (link)
  7. ^ Hackenberg, Timothy D. (1995). "Jacques Loeb, B. F. Skinner, and the legacy of prediction and control". The Behavior Analyst. 18 (2): 225–36. doi:10.1007/bf03392710. PMC 2733711. PMID 22478220.
  8. ^ The novel Arrowsmith, Paul de Kruif (1890-1971) and Jacques Loeb (1859–1924): a literary portrait of "medical science", H. M. Fangerau, Medical Humanities 32 (2006), pp. 82–87.
  9. ^ Mark Twain on the Damned Human Race, edited by Janet Smith, Hill and Wang, New York, 1994, pp. 45–49.
  10. ^ Rasmussen, Charles, and Rick Tilman. Jacques Loeb: His Science and Social Activism and Their Philosophical Foundations, Volume 229. N.p.: American Philosophical Society, 1998. Print. "An avowed atheist and materialist, he espoused secular humanism..."
  11. ^ Stout, Harry S., and D. G. Hart. New Directions in American Religious History. New York: Oxford UP, 1997. Print. Loeb was a forthright atheist..."


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