Lazzaro Spallanzani's opuscoli of 1776

Abstract

Lazzaro Spallanzani's (1729 to 1799) disputations with John Needham (1713 to 1781) and Georges Leclerc, Comte de Buffon (1707 to 1788), reached their apogee in 1776 with the publication, at Modena, of 'Physical Observations on Animals and Plants' (Opuscoli de Fisica, Animale e Vegetabile). The book is subtitled 'Observations and Experiments on Infusion Animalcula Occasioned by an Examination of some Articles from a New Work by Mr. Needham'. Included in this span of 304 pages (identified as 'Tomo Primo') are 2 letters, one quite long, one brief, written to Spallanzani in 1771, by Charles Bonnet (1720 to 1793), a well known preformationist, 'relative to ideas on infusion animalcula'. Most microbiologists appreciate the importance of Spallanzani's work on infusion animalcula. His conclusions were sharply outlined as one may gather from his statement: 'As I could not then conceal my propensity to believe, that infusion animalcula originated from germs, neither do I hesitate to say, propensity has become perfect conviction. If the animalcula do not originate from the vegetative power, I do not see how we can ascribe their origin to anything but eggs, seeds, or preorganized corpuscles, which we understand and distinguish by the name of germs'. 'Opuscoli' was not Spallanzani's first work dealing with the issue of generation mechanisms. In 1765 his 'Microscopical Observations in regard to the Generation Theory of Needham and Buffon' appeared, followed 4 yr later by Abbe Regley's French translation of Needham's work, 'New Investigations, Microscopical Discoveries, and the Generation of Organized Bodies'. This translation was furnished with copious 'notes'; the original work occupying only 138 pages, while the notes, which are, in fact, a detailed rebuttal of Spallanzani's experiments, occupy 159 pages. In Needham's view, some animalcula of infusions derive only from 'seeds', producing beings like themselves, and are present in the air and, therefore, in newly prepared unheated infusions; whereas those seen in vessels containing heated, sealed infusions, are resultants of the action of a vegetative force acting on the organic molecules constituting the infusion. In either case, all infusoria were considered to belong to the same class. It apparently never occurred to Needham to test the validity of his experimental conditions since he was quite blinded by the enormity of his great 'discovery'. Spallanzani was a preformationist and furthermore, an 'ovist'. He firmly believed that all parts of a new individual were preformed within the ovum. Spallanzani, along with A. Haller (1708 to 1777) and C. Bonnet, were the 3 great preformationists of that century. The work contra Needham and Buffon represented only a small facet of Spallanzani's investigations on generation, but it is the part relevant to microbiology.