(Re-)defining “animal magnetism”: the mesmerism investigations of 1784

TL;DR

This article re-examines the 1784 royal commission investigations into animal magnetism, arguing that the commissioners did not simply test and refute Mesmer's therapy but actively redefined what "animal magnetism" meant, inscribing their own assumptions about sensations, the imagination, and social order into their experimental protocols. The investigations are presented as "boundary-work" that simultaneously drew epistemic and social demarcations without closing the question of magnetism's credibility.

Key findings

• The commissioners privileged sensations as the observable proof of the magnetic fluid and assumed the fluid acted on individual bodies, whereas mesmerists like Mesmer and Deslon did not bind the fluid's existence to sensations or to individual (rather than collective) effects; the article thus contests Jessica Riskin's depiction of mesmerism as an already well-defined "sensationalist" doctrine.
• When results were non-uniform — the commissioners felt nothing, eight healthy subjects remained insensible, and at Passy "four out of seven subjects felt nothing, but three did" — they introduced the imagination as an alternative causal hypothesis, which transferred class as a new demarcation criterion (lower-class subjects were deemed to have weaker, imbalanced imaginations; upper-class patients reported feeling nothing).
• Sub-criteria of age and gender further mapped magnetic bodies: two insensible subjects were "little Claude Renard, a child of six" and "Geneviève Leroux, a nine-year-old," and women were held to have more vivid imaginations and to manifest convulsions more often than men.
• The commissioners redefined mesmerists' Hippocratic term "crisis" as harmful "convulsions," arguing these were auto-productions of the imagination that endangered individual health and, through contagion and imitation, the social and political order — a "politicisation" of the term.

Methods

• Historical study of the 1784 investigations, drawing predominantly on the royal commission's report (Académie des Sciences and Faculté de médecine), with the Société royale de médecine commission's proceedings noted as relatively similar but more focused on utility than causes.
• Analysis framed through the concept of "boundary-work," tracing how the commissioners' protocols translated assumptions about sensations, individual bodies, and magnetic gestures into experimental design.
• Close reading of the commission's experiments, including self-experimentation, tests on eight healthy subjects, the Passy trials on "really ill" subjects "from the class of the people," Jean-Baptiste Jumelin's imitation magnetisation on eight men and two women, and the blindfold experiments (including a fifteen-minute interval before Jumelin re-entered).

Limitations

• The paper states that "how the public debate further explored and developed these conceptions of the body and magnetism is material for a different article," so the reception and subsequent debate are not analysed here.
• The article explicitly focuses on the royal commission's report because it was "most influential," treating the Société royale commission's conclusions as relatively similar but less central — a scope choice evident in the text.
• The argument is interpretive and historiographical, positioning itself against older accounts of the investigations as a straightforward "scientific triumph of the experimental method"; it does not offer new archival experimental data beyond the reports and cited pamphlets.