PASTEUR (Louis). - Lot 248

PASTEUR (Louis). Journal des Savants. 1850. Article Chevreul. Autograph manuscript, [ca. 1860], 8 pages in-12, in modern black half-maroquin folder. Very interesting critical notes on fermentation, combining the names of Van Helmont, Chevreul and Pasteur. Pasteur synthesizes here the article by the famous chemist Eugène Chevreul (1786-1889) on Van Helmont, published in 1850 in the Journal des Savants. The Belgian physician and chemist Van Helmont (1557-1644), author of Ortus Medicinæ (1648), was, despite his highly debatable physiological theories, a pioneer in the study of gases and the discovery of gastric juice. In these reading notes, he summarizes Chevreul's article point by point, and ends by pointing out some of the Belgian physician's quirks and errors. Pasteur examines with Chevreul the two classes of ferments distinguished by Van Helmont: the other, alterable and destructible, which develops with the seeds produced by individuals of the same species, and to which Van Helmont still attributes the effect to a property he calls fermental virtue, which accompanies the seed during its formation, and disappears or dies as soon as the work is completed. He then turns to odor ferments, to which he gives very strange roles. Pasteur reports two very curious experiments carried out by Van Helmont and recorded by Chevreul: scorpions born from crushed basil, and mice from wheat grains! On the last page, he draws his own, rather critical, conclusion about Van Helmont: M. Chevreul's main aim is to demonstrate that Van Helmont was imbued with the a priori method, that his experiments were carried out solely, not to enlighten himself by seeking truths of which he was ignorant, but to support opinions conceived a priori that he wanted to establish as truths, even though many of them were errors. A curious proof," adds Pasteur, "is that Van Helmont claimed that the first day of creation was really only the second, because, counting only two elements, air and water, his system required them to have been created before all other bodies. This critical analysis is a valuable document on Pasteur's working methods.