Fritz Kahn’s Fantastical Journey Through the Body

There’s a scene in Everything You Always Wanted to Know About Sex* (*But Were Afraid to Ask) (1972) where Woody Allen re-imagines the body as a spacecraft. Up in the brain—depicted as mission control—tiny technicians direct the action. Meanwhile, down in the body’s nether regions, Woody, dressed as a “sperm” in a bright white jumpsuit, waits for the signal to deploy (it’s date night).

Woody might not have realized it, but he was nearly half a century late to this gag. By the mid-1920s, the German graphic designer Fritz Kahn was already experimenting with images that compared the body to a factory and brain circuitry to control panels. Kahn wasn’t just trying to be funny. His goal was a bit more exalted: educate the public about how their bodies worked using familiar machines and other objects as visual metaphors for biological processes.

A new book, Fritz Kahn, reacquaints us with this pioneer of popular science communication. Co-authored by the writer and Kahn scholar Uta von Debschitz and her brother, graphic designer Thilo von Debschitz, Fritz Kahn features 280 illustrations executed between 1914 and 1965. Sourced from books and magazines long out of print, the volume represents only 10 percent, roughly, of the designer’s massive output.

Kahn’s most enduring image, “Man as Industrial Palace,” appears on the cover. It shows a cross section of a man’s head and torso subdivided into a multi-tiered factory. In the brain, white-coated technicians (sound familiar?) run gland, muscle, hearing, and vision centers. In the “nervous center,” tiny secretaries operate a switchboard. Moving south, factory workers in the liver repackage sugar as starch-like glycogen and convert it back again. Woody would have been right at home.

Complex analogies like “Man as Industrial Palace” reflect Kahn’s hands-on knowledge of the human body. Throughout much of the 1910s and ’20s, Kahn led what he once described as “a double life”: hospital doctor by day, writer for a German science book club called Kosmos in his off hours.

With the ascension of Nazism, Kahn, who was Jewish, fled Germany in 1933 to Palestine, France, and then to America. (An old friend from his Berlin days named Albert Einstein helped him obtain a visa.) Despite the chaos, Kahn wrote and designed 10 books over his long career, including The Cell, The Human Body, and Our Sex Life. While he wasn’t a draftsman, Kahn worked closely with illustrators to execute his vision.

Fritz Kahn co-author Uta von Debschitz describes the designer as a man so in love with nature and the human body, he’d use any available analogy to communicate its workings to non-scientists. And she really means “any.” Take his image of a radish sandwich as a model for the cerebellum, she says. Here Kahn riffs off the repeating layers of a club sandwich (bread-filling-bread-filling-bread) to model the pattern of some circuits in the cerebellum, a brain region that coordinates balance and voluntary muscle activity. Bread slices represent what Kahn describes as “convolutions” in the cerebellum, while radishes inside the “sandwich” signify large neurons called Purkinje cells. (The vegetables’ leafy tops do look a bit like Purkinje cells’ branch-like dendrites). The skewers holding the sandwich together symbolize granule cells’ distinctive horizontal “T” fibers (also called parallel fibers), which pass through the Purkinje cells’ “leafy” tops to create synaptic connections needed to regulate movement. “I mean, that’s hilarious,” von Debschitz says of the sandwich metaphor. “On the other hand, it’s showing you a structure that is correct.” [Editor’s note: Kahn’s graphic is a simplied version of the cerebellum and its circuitry.]

Graphics weren’t Kahn’s only tool for demystifying science. While his captions could be surprisingly dry (a stark contrast to the near-psychedelic images they described), he could also be an engaging and whimsical essayist. Fritz Kahn includes three of Kahn’s essays, among them, a 1923 Kosmos article titled “Fairytale Journey on the Bloodstream,” which helped popularize the concept of a cell-scale journey through our body. The article follows a team of miniscule scientists who hitch a ride on a red blood cell. “We are sailing! In our cell boat on the red-gold stream of blood!” Kahn’s ecstatic narrator declares. “Farewell, realm of man!” Fans of the 1966 sci-fi flick Fantastic Voyage—which follows a similar conceit—might feel a twinge of déjà vu.

Kahn’s books were a hit with laypeople. But they also found a receptive audience among doctors. In the 1920s, the famed Swiss public health researcher Dr. Wilhelm von Gonzenbach even suggested that medical students read Kahn’s work as a prelude to their more specialized medical study, according to von Debschitz. Of course, science has progressed since Kahn’s day, and not all his images remain accurate. Diagrams positing connections between race and biology, for instance, reflect the now-discredited “science” of their day. Nevertheless, author Uta von Debschitz says popular science writers can still learn volumes from Kahn’s humor, experimentalism, and humility. Indeed, Kahn’s overarching lesson is timeless: Mankind has invented factories, elevators, electronic doorbells, and photography, but even the most advanced products of human ingenuity pale in comparison to nature’s great machines.

Von Debschitz points to a favorite Kahn graphic in which he compares a walnut in its shell to a human brain nestled in its skull. In German, “If you really want to insult somebody, you say, ‘You dumb nut!’” she says. “In this [picture’s] case, it’s just the opposite. Kahn says, “‘The nut isn’t dumb. It has the same structure as a brain.’” Kahn is reminding us, she says, “that we are part of nature. We are not superior to it.