From the start, though, the use of dogs for violent laboratory experiments disturbed a bourgeois sensibility that associated them—or at least the purebreds—with family and the comforts of domestic life. (Many years later, Julia Lakavage would tell reporters that Pepper and her other dogs were "like family members … children that don't grow up.") That notion extended to the very upper reaches of society: Queen Victoria of England—whose menagerie of pets included Skye terriers Islay, Cairnach, and Dandie Dinmot; King Charles spaniel Dash; greyhound Nero; mastiff Hector; and many more—was well-known to be suspicious of the new science of animal experimentation. In 1875, the year before the passage of Britain's Cruelty to Animals Act, Victoria asked Joseph Lister to speak out against vivisection: "The Queen has been dreadfully shocked at the details of some of these practices," her secretary wrote, "and is most anxious to put a stop to them."
By the first decade of the 20th century, the plight of research dogs had become the principal cause for animal activists, who singled them out on account of their vulnerable nature—and the ease with which they could be used to elicit public support. In February 1903, a pair of Swedish animal lovers slipped into a medical demonstration at University College London and watched physiologist William Bayliss cut open the neck of a brown dog. In their published account of the episode, they claimed that the animal had suffered under improper anesthesia. Riots erupted after a monument was erected to the anonymous brown dog. (Tensions over the "brown dog affair" have been revived in England several times since.)
Scientists responded to the furor over experimental dogs with anger and derision. Historian Susan Lederer cites a 1910 screed by a New York physician who accused the anti-vivisectionists of suffering from a kind of "zoophilic psychosis": They "interest themselves not so much in experiments upon fishes, insects, pigeons, rats, mice, snakes, nor in cruelties to men, cattle, chickens, and sheep," he wrote. "Their interests are bent towards those useless animals which can be made the objects of fondling and which compared with other animals play a minor role in the great field of scientific experimentation."
Within a few years, the concern over experimental dogs crystallized into a fear that pets were being stolen and sold to research institutions. The specter of "dog-napping" became central to the activist rhetoric starting in the 1910s, says Lederer, and soon showed up in animal-welfare exhibitions and pamphlets with titles like Guard Your Dog. Meanwhile, the dog-theft meme percolated through the media—and not only in the newspapers of ardent anti-vivisectionist William Randolph Hearst. In the early 1920s, the New York Times offered regular coverage of a gang of "auto-pirates" who pilfered more than 150 animals from wealthy estates on Long Island. That story, and others like it, were summed up in a Times headline from February 1922: "Stealing Fine Dogs a Regular Industry … Most Intelligent of Their Kind, but Have Never Learned How Not To Be Stolen."
The epidemic of pet theft received intermittent coverage over the next few decades. With the re-emergence of the animal welfare movement in the 1960s—and the disappearance of Pepper in Pennsylvania—it became a national story.
At the turn of the century, animal activists organized their campaigns around research dogs and cats, but science was already moving in a new direction. Mendel's ideas had been rediscovered in 1900 and the term genetics coined in 1906; the new science of heredity created a sudden need for organisms whose exact ancestry was known and controlled. Within a few years, the perception and practice of biomedical research had begun to diverge: While humane societies were worrying about missing pets, researchers were shifting to a new set of standardized, purpose-bred laboratory organisms—the rat, the mouse and the fruit fly.
The standardization of laboratory animals reflected the growing influence of industrial engineering in America. Under the new paradigm, research organisms could be seen as a sort of raw material for use in a knowledge assembly line. Just 10 or 20 years earlier, a physiologist might have conducted his experiments on a variety of species—frogs and rabbits, for example, or dogs, horses, and baboons—to show that a finding could be generalized across the whole of creation. Now, whatever could be demonstrated in a rat or a mouse was assumed to be true of a dog, a horse, or a human. The growth of statistical science also changed the nature of laboratory work: Now it was advantageous to increase your N by repeating an experiment as many times as you could on as many animals as were available.
Biomedical science became even more industrialized during the postwar period as government money flowed through the pumped-up National Institutes of Health. Grants officers realized that animals could be most efficiently distributed if they were churned out in large numbers at a few, centralized locations. Meanwhile, the organisms themselves had begun to be packaged as commercial products: In 1941, the breeders at the Jackson Laboratory in Maine received a patent on their line of "JAX Mice" research animals; a year later, the Wistar Institute in Philadelphia trademarked its own line of "WISTARATs."
Experimental dogs had been well-suited to the old-fashioned, artisanal mode of inquiry—William Harvey cutting open a heart, Christopher Wren pumping a vein full of wine, Richard Lower transfusing blood with a chain of quills. But as an instrument of modern science, they were starting to look obsolete. The economics of breeding dogs were one problem: In 1965, the year Pepper was taken, a dog could be raised and maintained in a research lab for about 70 cents per day. At that rate, though, it would cost more than $250 to produce a single, sexually mature animal. A stray with uncertain heritage could be had from a dealer for just $15, which explains why hospitals were buying dogs like Pepper to begin with.
That's not to say dogs didn't have their niche in biomedicine. Medical schools, in particular, made ample use of them for education and research in surgery and cardiology. And many of the landmark studies on anemia, diabetes, hemophilia, and cardiothoracic surgery used dogs. But by the time of Pepper's death, there was already a move toward replacing canines on the operating table with a brand-new model organism—the miniature pig. The hairless and docile Yucatan mini-pig had been introduced to the United States in 1960, and the University of Missouri opened a dedicated miniature swine production facility in 1965.