Leiden University boasted one of the most popular and influential medical schools of the mid-seventeenth century, drawing hundreds of students yearly from across Europe. These students participated in the revival of frequent clinical instruction, anatomical and chymical experiments, and even tests of supposed disease-causing substances and remedies on living animals and humans. Students and professors treated their subject dogs as chymical apparatus, made alive and ill by the well-tempered or preternatural chymical mixture of acids and alkalies in their bodies. Into these living canine chymical laboratories, the students injected chymical substances suspected of pathogenic properties, then examined the cadaver for the lesions of disease. They also directly tested chymical remedies on animal subjects after introducing disease agents. Comparing records of cases from the clinic with the medical professors’ treatises and student disputations shows that old and new theories of disease and drug action were hotly contested and often tested, including the claims of the leading professors at the school. This was a clear site not only of the union of chymistry, postmortem autopsy, anatomical experiments, and clinical tests, all aimed at discovery—but also of thriving clinical medicine well before its supposed Foucauldian birth date.