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Definition: Loeb from Collins English Dictionary


1 Jacques (ʒɑːk). 1859–1924, US physiologist, born in Germany, noted esp for his pioneering work on artificial parthenogenesis

Summary Article: Loeb, Jacques
From Encyclopedia of Life Sciences

(1859-1924) German -born physiologist best known for his work on artificial parthenogenesis in animals.


mechanistic life processes

animal tropism


Jacques Loeb was born in Mayen, Germany to a prosperous Jewish importer, and grew up in a well-educated home reading the classics of eighteenth-century European philosophical thought. When he first entered university in 1880 in Berlin, it was with the intention of studying the philosophy of the will, but he was so disillusioned by his experience that he abandoned these plans and moved to the University of Strasbourg to study science. He obtained an MD in 1884 and in 1886 moved to the University of Wurzburg as an assistant to the physiologist Adolf Fick. Toward the end of his tenure there he spent a winter at the marine biological laboratories in Naples. In 1890, Loeb married an American student named Anne Leonard and, disturbed by the German political scene at the time, emigrated to the USA the following year. There he taught at a number of universities including Bryn Mawr College (1891-1892), the University of Chicago (1892-1902), and the University of California at Berkeley (1902-1910); he finally worked at the newly established Rockefeller Institute of Medical Research in New York City where he remained until his death. Throughout this period, Loeb spent his summers in the marine biological laboratories at either Pacific Grove in California or Woods Hole in Massachusetts, where he did most of his experimental work.

Perhaps because of the popular interest in the subject, Loeb is best known for his rather controversial work on artificial parthenogenesis in animals, but in fact he made several contributions to biology long before becoming active in that field. He was one of the pioneers in the area of objective analysis of animal behaviour and is often credited with introducing experimental rigour into this area of biology. He operated under what he termed a 'mechanistic' conception of life (which he used as the title of what emerged as the most widely read of his books), namely that all of life's processes, including behaviour, could be explained in terms of physical or chemical reactions or mechanisms. This mechanistic theory appears as a common thread in most of the science that Loeb undertook - beginning with his medical school thesis, which focused on the localization of brain function, specifically the effects of injuries to the cerebral cortex on blindness. See also Cerebral Cortex Diseases and Cortical Localization

In 1888 he began a line of research that demonstrated animal tropisms, namely the instinctual movement of certain animals towards external stimuli such as light, electric currents or chemicals. Specifically, he devised experiments to show that species of caterpillars invariably preferred to move toward light sources, typically the sun. During his winter in Naples, Loeb's interests were turned to problems in development and embryology, and he began to apply his mechanistic philosophies to problems in these fields as well. By adjusting salt concentrations in the environment of sea urchin eggs, he was able to induce artificial parthenogenesis, namely the division of eggs to give rise to larvae without prior fertilization with sperm from the animal. In 1918 he embarked on a third line of research through which he attempted to explain the action of proteins in living systems in terms of their properties in solutions, and made important contributions to understanding the colloidal behaviour of these molecules. Loeb was one of the few scientists of his generation who was as well known to the general public as within the field. Perhaps the best evidence for this is in Sinclair Lewis' 1925 novel Arrowsmith, where the character modelled on Loeb is the only figure within the fictitious scientific institution (an obvious satire of the Rockefeller Institute) to emerge in a positive light. See also Egg Activation

Further Reading
  • Loeb, J (1912) The Mechanistic Conception of Life; Biological Essays. Chicago: University of Chicago Press.
  • Loeb, J (1922) Proteins and the Theory of Colloidal Behavior. New York: McGraw-Hill Book Company.
  • Lewis, S (1925) Arrowsmith. New York: Grosset & Dunlap.
  • Osterhont, WIV (1928) Jacques Loeb. Journal of General Physiology 8: ix-xcii.
  • Neeraja Sankaran
    Yale UniversityNew Haven, Connecticut, USA
    Wiley ©2007

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