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ELIE METCHNIKOFF (1845-1916): Elie Metchnikoff was a Russian biologist, zoologist and protozoologist who is best remembered for his pioneering research work into the immune system of living organisms. Immune system comprises of a series of specific cells, tissues and organs (for example, white blood cells, spleen, antibodies and thymus) of the body of living organisms which protect it from diseases and infectious agents. Metchnikoff was an associate of Louis Pasteur, and he was the first to coin the word “phagocytosis” – to mean “the eating of cells (particularly microbial or pathogenic cells) by a special type of white blood cells called phagocytes. Phagocytes are specific cells of the body (for example, white blood cells) which can surround and destroy other pathogenic cells (for example, bacteria) after invading the body of a living host.


Metchnikoff demonstrated in his works that certain body cells (which he called phagocytes) moved to damaged areas of the body where they eat invading bacteria. He called the process phagocytosis, and proposed the theory of cellular immunity. Though his theory that certain white blood cells could engulf and destroy harmful bodies such as bacteria where greeted by skepticism from other scientist including Louis Pasteur. Elie Metchnikoff was awarded the Nobel Prize for medicine or physiology in 1908 for his work on phagocytes. Elie formulated the basic theory on which the foundation of immunology lies, by accounting that the body is protected from infection by leukocytes or white blood cells that engulf bacteria and other invading organisms (a process called cellular immunity). Elie Metchnikoff is often referred as the father of immunology because of his innovative work on the immune system of higher organisms.


Abbe Lazzaro Spallanzani was an Italian naturalist/biologist, priest and physiologist who made significant contributions to the concept of biogenesis, a belief that life begat life. Lazzaro criticized John Needham’s work on spontaneous generation, and he was one of the first scientists as at the time that criticized the theory of spontaneous generation (abiogenesis). Abbe Lazzaro showed in his experiments that microorganisms can be killed by heating (boiling). In 1769, he performed series of experiments on the subject matter (abiogenesis) which showed that heating can prevent the appearance of animalcules in infusion (depending on the degree of heating).

Abbe Lazzaro Spallanzani was not satisfied with Needham’s work of only using cork to seal the flask, and thus he hermetically sealed the flask in order to prevent its content from coming into contact with atmospheric air. He boiled meat and vegetable broth for a very long time in a flask and then sealed the neck of the flask by melting it. As a control, he briefly boiled the contents of some flasks, left some open to the air, and the others partially sealed with corks. After two days, Lazzaro discovered that sealed flask infusions remained barren for long days (and without organisms) while the control flasks were swarming with some organisms. Abbe Lazzaro Spallanzani concluded that organisms will not appear unless new air entered the flask and come in contact with the meat infusion.

He also commented that external air might be needed to support the growth of small animals (animalcules) already present in the medium, a notion which was welcomed by supporters of spontaneous generation. His works on this area were very good, but nevertheless, faulty experiments continued to be performed, and evidence was gathered in favour of spontaneous generation. John Needham objected to the findings of Lazzaro with the reason that Spallanzani had destroyed the “vital force of life” with the excessive amounts of heat he applied in his experiments. Vital force of lifeis a hypothetical, non-physical, and non-chemical force used by biologists to explain the reason for the evolution and development of living organisms. This force was used by scientists as at the time abiogenesis was widely believed, to explain how living organisms may have evolved and developed.

Further reading

Brooks G.F., Butel J.S and Morse S.A (2004). Medical Microbiology, 23rd edition. McGraw Hill Publishers. USA. Pp. 248-260.

Madigan M.T., Martinko J.M., Dunlap P.V and Clark D.P (2009). Brock Biology of microorganisms. 12th edition. Pearson Benjamin Cummings Publishers. USA. Pp.795-796.

Nester E.W, Anderson D.G, Roberts C.E and Nester M.T (2009). Microbiology: A Human Perspective. Sixth edition. McGraw-Hill Companies, Inc, New York, USA.

Prescott L.M., Harley J.P and Klein D.A (2005). Microbiology. 6th ed. McGraw Hill Publishers, USA. Pp. 296-299.

Singleton P and Sainsbury D (1995). Dictionary of microbiology and molecular biology, 3d ed. New York: John Wiley and Sons.

Slonczewski J.L, Foster J.W and Gillen K.M (2011). Microbiology: An Evolving Science. Second edition. W.W. Norton and Company, Inc, New York, USA.

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