According to Gerald Geison, of Princeton University, the French scientist also acted unethically by using a rabies vaccine on a child that he claimed to have tested on hundreds of dogs.
In fact he had tried the vaccine on only a handful of animals, Professor Geison told the annual meeting of the American Association for the Advancement of Science in Boston.
'Pasteur would not have passed muster with our current ethical committees,' he said.
Professor Geison has examined Pasteur's 'microscopic' scribblings in more than 100 laboratory notebooks deposited at the Bibliotheque Nationale in Paris, and said he had found 'striking and sometimes astonishing discrepancies' between these and Pasteur's published science. Pasteur is best known for demonstrating the sterilising effect of pasteurisation, but is also remembered for his groundbreaking work on the anthrax and rabies vaccines.
The work helped him, and his Pasteur Institute in Paris, to become extremely wealthy. But at the time one of his colleagues, Emile Roux , refused to take part in Pasteur's rabies vaccine trial on a peasantfrom Alsace, Joseph Meister, who had been bitten by a rabid dog, because he felt Pasteur had carried out too few trials on animals to experiment on people.
Pasteur's notebooks show that on many occasions he claimed to have carried out more experiments than he had, and sometimes reversed the order in which he had conducted experiments when he came to write them up.
Professor Geison said historians had uncovered discrepancies between the notebooks and published papers of other leading scientists, including Michael Faraday, Claude Bernard, a leading 19th-century physiologist, and Hans Krebs, the Nobel laureate who worked on energy transformation in biological cells.
But Pasteur's conduct over his anthrax trial was harder to excuse, he said. Pasteur had claimed to be using a vaccine weakened by exposure to oxygen. In fact the successful trial involved a vaccine weakened by an antiseptic, an approach developed by a veterinarian, who remained in obscurity.
Pasteur apparently decided to lie after boasting so often that he could make a successful oxygen- attentuated vaccine that he was eventually challenged to carry out a demonstration. He did succeed in perfecting his original vaccine, but not until after the public trial.
Professor Geison said he did not wish to tarnish Pasteur's reputation. He said the public harboured a misconception that science proceeded by a set of rules. In fact, the process was often carried out in haste, with the 'exaggeration and tidying up' of results.
Practices some people might see as scientific misconduct were often a necessary part of the 'risk-taking and boldness' that produced truly great science, he said. 'It is not part of my purpose to deny Pasteur's greatness as a scientist. Science is not a simple- minded mechanical application of objective scientific method.'
Professor Geison was forgiving in his final analysis: 'Once we know of Pasteur's deviations from currently correct scientific procedures, do we really wish he had behaved otherwise?'