Sixty years before Gregor Samsa awoke to find himself transformed, another confrontation between man and bug: this time, between the common flea and an off-kilter fellow in a three-piece suit. Falling backward in his chair, the gentleman brandishes an ax and a pair of shears. Atop him already, a massive pale-yellow P. irritans specimen. As things stand, it’s anyone’s game.

The scene is captured in sharp detail on a glass slide for magic lanterns: a popular form of entertainment from the eighteenth century until the early twentieth. Illuminated by gas lamp or limelight, The Attack of the Monster (pulex irritans) would have once filled a screen in a lecture hall or theater. This slide was produced around 1855, at the dawn of the magic lantern’s Victorian heyday, by the Philadelphia photography studio W. & F. Langenheim.

Established by the German immigrant brothers William and Frederick Langenheim, the studio became one of the most commercially successful in America, turning out stereo views of tourist attractions and daguerreotype portraits. Among other technical advancements, the pair also pioneered an innovative new method for capturing photographic negatives on glass. Until then, lantern slides had been limited to hand-painting and transfer prints. The Langenheim’s “hyalotype” process, patented in 1850, introduced a new world of possibilities.

The Attack of the Monster puts the Langenheims’ photographic chops on show, using Frederick as a model. The exposure time for early hyalotypes could be as long as one minute, making portraiture challenging even with the help of clamps and braces to help models hold still. Combined with a microscopic flea, the image is a feat of practical effects.

Stranger still than the slide’s subject is where it was found. Now held at the National Library of Medicine, The Attack was originally owned by Saint Elizabeths Hospital in Washington, D.C. The first federally funded psychiatric institution in America, Saint Elizabeths opened in 1855. At the time, Dr. Thomas Story Kirkbride — the director of the Pennsylvania Hospital for the Insane, famous as the father of modern psychiatry and as an advocate for the “moral treatment” of the mentally ill — was in the midst of developing a therapeutic model in which magic lantern slide shows played a key role.

The Pennsylvania hospital introduced lantern-accompanied lectures as evening entertainment for patients, physicians, and orderlies alike. In them, Kirkbride believed he had found the ideal entertainment for the mentally ill. In 1858, he wrote that “even those who think little of the remarks that are made, find pleasant occupation in looking at the pictures which are before them”. But more than mere entertainment, magic lantern shows (especially photographic ones) were thought to have medical potential. The historian Emily Godbey writes that to Kirkbride, photography was “the perfect vehicle with which to transmit more accurate images to the mind”. The magic lantern shows, whether accompanying technical lectures on optics and natural science or illustrating world travel narratives, were a kind of “direct mental treatment” to help patients think more rationally.

Researchers believe that the magic lantern slides in Saint Elizabeths served a therapeutic role too. How, if it all, this battle between man and flea may have contributed remains unclear.