Photo credit: JacobStudio/Thinkstock
By Daniel Engber
I’ve killed birds by suctioning their brains, and I’ve sacrificed the lives of tiny kittens. I’ve withheld water from a live macaque. But in all the time I spent in graduate school for neurobiology, the most diabolical procedure that I performed in the name of scientific research—the one that haunts me still—was my very first: the perfusion of a mouse.
That begins with the animal etherized upon a lab bench, its paws spread wide and secured with tape. I’d snip the skin of its abdomen with a pair of nail scissors, and separate the muscle to expose its heart, smaller than a hazelnut and still beating. The mouse’s own circulatory system would become my instrument, pumping a preservative throughout the mouse’s veins and arteries, so as to pickle every cell inside its body. First I’d poke a hole in the right atrium of the heart, allowing all the blood that’s flowing in to drain into the body cavity. Then I’d slide my syringe into the left ventricle and start feeding it with paraformaldehyde—only so much as the organ could press out with its diminishing contractions. A few minutes later, all the mouse’s vessels would be flushed, made pallid by the chemical, and repurposed for my use. The animal, split open on the table, would have mummified itself before my eyes.
I don’t believe the mice suffered all that much during this process—I’d pinch their feet as I anesthetized them to make sure they were really out, and the procedure had been approved by a standard institutional review committee at my school. But in truth I’d never worked with mice before and had no way to intuit their well-being. (It’s much easier to see pain in the face of a monkey or a cat.) At any rate, it was clear enough that these rodents were disposable: If one perfusion didn’t go so well, I’d simply reach into the cage and grab another mouse. It seemed as though the rules for working with these animals were different from the ones for other species. Bigger, more likable animals were sacrificed for research. Mice were used.
I only learned much later that this disparity has been ensconced in U.S. law for half a century. The Animal Welfare Act, signed by President Lyndon Johnson in August 1966, enforces an apartheid system of concern for animal suffering. This has been the case for most of the law’s history, though in its original formulation, it was intended to protect all warm-blooded animals in the lab. (It was also meant to address a national panic over dognapping.) “Science and research do not compel us to tolerate the kind of inhumanity which has been involved in the … careless and callous handling of animals in some of our laboratories,” Johnson said that summer, at a signing ceremony that was strategically small and out of sight. But within a few years, the U.S. Department of Agriculture—the agency responsibly for implementing the new law—had decided that the rats, mice, and birds in science labs were simply too numerous to be protected. “The math just did not allow it,” a former department official told me several years ago, for another article in Slate. “We couldn’t use the National Guard to make all of these inspections. We didn’t have the force.” On the basis of that calculation, these species were formally excluded.
As we approach the 50th anniversary of the Animal Welfare Act, it’s worth reviewing the legacy of this decision, in both practical and symbolic terms. Rats and mice remain trapped in a special, unprotected category, although they compose a large majority of research animals around the world. Efforts to refine experiments and make them more humane has led to broad reductions in the use of many different species: Numbers from the USDA demonstrate that experiments on protected animals—dogs, cats, and monkeys; rabbits, hamsters, and guinea pigs; and so forth—have been dropping over time and are at a record low. Still, figures on the use of rodents suggest a rapid upward trend. In European labs, rats and mice together represent about four-fifths of experimental vertebrates (a category that includes mammals, fish, birds, reptiles, and amphibians), and their global use now results in more than 100,000 published papers every year.
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