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loaca is a 33-foot-long machine that simulates human digestion. Housed in New York’s New Museum of Contemporary Art in Soho, the technological/artistic entity represents a meeting of the minds of Belgian artist Wim Delvoye and scientists from the University of Belgium in Antwerp. Museum staff feed Cloaca twice daily with food from local restaurants. The device digests for 22 hours and eliminates once daily, at 2:30 p.m.

Cloaca digests but does not absorb. What is digestion without absorption? A lot of waste.

As a gastroenterologist and teacher of digestion and absorption, I was curious to visit the exhibit. So I went on a recent Saturday early afternoon. Before going, I imagined Cloaca would look like a long tube, akin to the human stomach and the small and large intestines.

Instead, Cloaca is a series of six large glass jars connected by tubing and run by an antiquated circuit board, locally and via the Internet. A large glass funnel connected to a meat grinder (a correlate to the mouth) sits quietly on a raised platform at the head of the machine. The machine had “eaten” eggs benedict in the morning and was digesting its dinner from the night before. Each bottle contained fluid, maintained at body temperature, at various stages of digestion. The suspensions swirled under the control of magnetic bars, not unlike in a laboratory.

The only visible activity for most of the day was the tedious process of digestion. Labels identified the first three bottles as acid, pancreatin, and bile, simulating the stomach, pancreas, and liver. The machine added pancreatic enzymes and bile into the bottles sequentially rather than together as occurs in the human intestine. The last three bottles contained brown slurries titrated with acid and base to maintain a pH near optimum for digestion, a simulation of the small and large intestine.

Each glass bottle had a tight lid on it. I thought of the millions of bacteria in the distal intestine, the distensibility of the colon, and its capacity to absorb and release gas. I had questions. Are human colonic bacteria in the system? If so, how is the gas generated by bacterial metabolism of nutrients decompressed? Why didn’t the rigid glass bottles explode? I looked to the museum attendant for answers. Yes, human colonic bacteria are present in the bottles. Whose they are and how they got there was not known. Gas is released from the system at night when no one is around, so as not to offend the patrons.

Overall, I felt let down by the purely mechanical portrayal of the digestive tract, a glorious and complex system with rhythmic motility and elegant feedback loops—a tract I spent much of my life studying. I felt nothing for this device.

Then came a pivotal moment—elimination. The crowd started gathering at the rear of the system where an 8-foot-long, glass-enclosed metal contraption stood. Earlier in the day, digested slurry had been dumped into a metal trough covered with filter paper. The nutrient-rich liquid phase was discarded into a plastic bottle and the solid waste stored in a vertical cylindrical stainless steel tube. We, about 100 strong, peered through the glass enclosure to watch the act of elimination. Unlike the fresh air up front, the air was less pleasant in the rear. The crowd got noisier as the time of elimination—2:30 p.m.—got closer. A French couple chatted and kissed. And then it happened, a brown flop onto a green conveyor belt. There were ughs, giggles, and applause. Overall the crowd was in good spirits, relieved. A woman next to me remarked, “I had a great view.” A child shrieked “caca, caca.” At last Cloaca came to life. I was a voyeur at Cloaca’s most private time. For a moment I felt shame, then I was amused.

What Mr. Delvoye has created is quite astonishing, a machine that produces human flop. The product is uniquely human because the machine is fed a human diet, the unabsorbed nutrients promote growth of the human colonic bacteria—a major component of fecal waste—and there is little overlap between human colonic biota and that of other animals. The only element missing is cellular debris normally shed from the gastrointestinal tract.

Though not a normal topic of discussion, much less for public viewing, Mr. Delvoye spent quite a lot of time and money to recreate what we do quite naturally—and when we do it, the result provides tangible proof our digestive tract is working properly.

The Cloaca exhibition continues until April 28. Dr. Carol Semrad is an associate professor of clinical medicine at P&S. Robin Eisner, editor of In Vivo, provides editorial guidance for Point of View contributions.