Benjamin Franklin thought that an excess of electric fluid gave rise to positive electricity, and a deficiency of the fluid to negative electricity. ‘New flannel, if dry and warm, will draw the electric fluid from non-electrics.’ By an electric he meant substances such as glass, and indeed the air. I’m not sure how much we think of electricity as a fluid today. James Thurber’s mother worried that it would run out of the sockets unless one left a plug in them, but she was perhaps unusual. Flann O’Brien put forward the similar theory that darkness was due to the accretion of ‘black air’.
Fluid mediums persisted in our world view because it was hard to think of things like electromagnetic waves without something for them to make waves in. That is why aether or ether lasted as a notion from the 17th century until into the age of television. In the 1770s the ‘imaginary fluid’ of ether was explained, by a sceptic, as the propagator of heat, light,muscular motion and gravity.
At a social level, the idea of body fluids caught the 20th-century imagination. ‘What about the fluid of Cotunnius?’ my husband has just piped up. What, indeed? It lies in the cochlea of the ear and is named after Domenico Cotugno, born in 1736, who published De aquaeductibus auris in 1761, sensibly writing in Latin so that everyone could understand him, which is why his name is remembered, if at all, in the Latin form.
Anyone but my husband thinks of something else when they hear the term body fluid. Nor do they usually think of blood, sweat and tears. It is in this context, I think that we should examine the vogue phrase gender fluid. Here, of course fluid is an adjective, as mad is in sex mad. Gender fluid is not an imaginary fluid that gives rise to gender, though it might well have been. It is the quality of possessing no gender that can’t flow into another form, as in a balloon filled with water.
No theory of fluids is too foolish to lack aggressive advocates: mephitic vapour, plogiston, animal spirits, mesmeric fluid, animal magnetism, vril, brain-waves, hysteric vapours. Gender has joined them as the most fluid thing of all