Prévost, Isaac-Bénédict

PRéVOST, ISAAC-BéNéDICT

(b.. Geneva, Switzerland, 7 August 1755; d. Montauban, France, 10 June 1819)

natural philosophy, mathematics, physics, chemistry.

Prévost was an astute observer whose knowledge of the sciences was largely self-acquired. His memoir of 1807 on the cause of the smut or bunt of wheat was remarkable in its time and its validity has endured. Although its implications in identifying a plant parasite as the agent of the disease were not fully appreciated then, the work later became influential and contributed to the background against which developed an understanding of contagious disease.

The son of Jean-Jacques Prévost and Marie-Élisabeth Henri, young Isaac-Bénédict was sent to a nearby village boarding school but had neither the disposition nor the opportunity to obtain more than the essentials for his later scholarship. He worked briefly as an engraver’s apprentice and then as an apprentice in a grocery house, where he mulled over questions of weight and force, odors, and other subjects that were later to concern him. Deciding against a commercial career, he resolved instead to devote himself to the sciences. He became tutor to the sons of M. Delmas of Montauban; Montauban was his home and the family were his friends until his death. Encouraged by the family, Prévost decided to give his full energies to his studies, and he set out to remedy his education. At first, he was most attracted to mathematics but later turned to physics and natural history, which he was able to study when the family spent part of each year in the country. Although the necessary books were sometimes hard to obtain, he persevered in reading, observing, and experimenting.

A founding member of the Société des Sciences et des Arts du Département du Lot in Montauban, Prédvost belonged to a number of learned societies and corresponded with many colleagues, including his cousin Pierre Prévost. He communicated papers on various subjects to the scientific journals and established himself as a savant. Although he had declined in 1784 an offer to succeed Pierre Prévost at the Berlin academy, he later accepted an appointment (1810) as professor of philosophy at the new Protestant academy in Montauban.

La carie or charbon (the bunt, smut, or stinking smut of wheat) was vastly destructive of crops when Prévost began a ten-year study to find the direct cause of the disease. Within the affected kernels, forming a dark powder, were the particles Tillet had described but considered a contaminating virus (1755). Prévost examined these brown-black, spherical granules beneath the microscope and estimated that millions were contained in a bunted kernel. He noted their likeness to the globules seen in certain uredos and recognized them specifically as the seeds of a cryptogam. By placing the spores in water, he was able to cultivate microscopic plants: and with the use of controls, he experimented in the fields to observe the destruction of young wheat plants. Although he could not discern the mycelia, he inferred that the penetrating parasite ultimately reached the kernel, there forming its gemmae. Prévost also discovered that copper solutions (particularly copper sulfate) can prevent the disease.

In 1807 Prévost finally identified a fungus parasite as the causative agent. Since at that time the spontaneous generation of lower plants was still an accepted hypothesis, Prévost’s discovery was extraordinarily important. His work gained wider recognition in 1847, when the Tulasnes cited his memoir in their own studies.

BIBLIOGRAPHY

I. Original Works. Prévost’s most important work was Mémoire sur la cause immédiate de la carie oú charbon desblés, et de plusieurs autres maladies des plantes, et sur les préservatifs de la carie (Paris, 1807), trans, by George Wannamaker Keitt as Memoir on the Immediate Cause of Bunt or Smut of Wheat, and of Several Other Diseases of Plants and on Preventives of Bunt., Phytopathological Classics, no. 6 (Menasha, Wis., 1939).

II. Secondary Literature. The main source on Prévost’s life and character is Pierre Prévost, Notice de la vie et des écrits d’ Isaac-Bénédict Prévost (Geneva—Paris, 1820), which describes published and unpublished works, journals, notes, and correspondence. A shorter biography, P. P. [Pierre Prévost], “Prévost, (Isaac-Bénédict),” is in the Biographic Universelle, Ancienne et Moderne, XXXVI (1823), 59-60. Keitt (see above) includes a biography and an evaluation of the Mémoire; see also G. W. Keitt, “Isaac-Bénédict Prtvost, 1755-1819,” in Phytopathology, 46 (1956), 2-5; E. C. Large, in The Advance of the Fungi (New York, 1940; 2nd ed., 1962), 76-79, also assesses Prévost’s work.

Gloria Robinson