How Pasteur turned over new fields

In his chosen field, Louis Pasteur made an unpromising start: he failed a first attempt to obtain the degree of bachelor of science and, although he passed the following year, he obtained only a mediocre grade in chemistry and - in a competitive entrance examination for the Ecole Normale - he came only 15th in a group of 22. But what Pasteur lacked in precociousness, he more than made up for by what his latest biographer, Patrice Debré, has called his progression of ideas, his synthetic ability and his stubborn refusal to be beaten by any problem or person.

On his way to achieving a new type of national heroism, Pasteur became the first person to reduce the virulence of micro-organisms, and the first exponent of two new subjects: microbiology (the study of microbes) and immunology (the study of resistance to infections). As a professor of immunology specialising in Aids, Debré stands on the frontier between the two subjects confronting one of the problems caused by microbes being free to change not only in directions forced upon them by makers of vaccines but also in directions that threaten to defeat the body's main defence against infections. With this background, Debré was an obvious choice of author for a biography that was intended to mark the centenary of Pasteur's death and to be part of an array of special ceremonies, seminars, congresses and articles. What was not anticipated was simultaneous publication of a book ( The Private Life of Louis Pasteur by Gerald Geison) that purported to show that the standard Pasteur legend needs to be qualified, even transformed, and that Pasteur had failed to give credit where credit was due and was not above deliberately deceiving his scientific peers. There were many angry responses to these suggestions, but Debré sensibly leaves his readers to find in Louis Pasteur "information that does not fit the interpretation of the American historian or, rather, permits them to form their own judgement by observing the experimental procedures of the 19th-century scientist".

In the course of describing these procedures, and retelling the famous stories with a wealth of interesting comments and anecdotes, Debré has many opportunities to sketch portraits of the French scientists who helped or hindered Pasteur during early and late phases of what proved to be a steady ascent to the top of a greasy pole. One of the highlights comes when Debré - after painting a portrait of Claude Bernard and describing how he came to befriend the younger Pasteur - compares the contributions made by the famous pair to a still relevant debate on the experimental method. Bernard - who succeeded in uniting anatomy and chemistry through animal experiments, but died before the germ theory of disease was fully confirmed - saw disease as a disturbance of the internal, cellular environment, ie the endogenous concept. Pasteur - whose genius lay in establishing revolutionary connections between hitherto separate branches of science - saw disease as microbic invasion of the body, ie exogenous.

Today we can see that the two concepts coexist with and complement each other. But it is good to be reminded that this knowledge came partly from a physiologist who "made use of chance and was able to launch himself wholeheartedly into a path he could barely discern"; and partly from a chemist who "passionately wanted to overcome all obstacles and accumulate proofs to support a theory that was quite frequently formulated before any experimentation had taken place".

Unlike Bernard, who had no notions of productivity or profitability, Pasteur eventually raised enough money to build and endow an independent research institute, and thus provide a home in Paris for a whole generation of his disciples. He did not live long enough to observe the experiments, performed in his institute, that - by showing that immune-system reactions are not restricted to live pathogens - finally made it clear that immunology is the study of how multicellular organisms learn to distinguish between what does and does not properly belong to an individual or a species. Nevertheless, as Debré shows in his final chapter, Pasteur continued to receive a share of the honours conferred on younger associates, and still richly deserves to be a favourite hero of France.

Though Debré has opted for a methodological rather than a chronological presentation of the various research topics, he has included in his splendid biography a detailed chronology of events between 1822 and 1895. Furthermore, Louis Pasteur has been so well served by Elborg Forster that this translation reads as smoothly as though it was originally written in English.

Professor Alice M. Stewart is honorary professor, University of Birmingham.