Analysing the transformations of veterinary knowledge throughout the 18th and 19th centuries, this article aims to shed a new light on the professionalization process of French veterinarians from the creation of the Schools in 1762 to their first monopoly on animal medicine in 1881. At the crossroads of human medicine and agriculture, the veterinary body used to share its competences with other occupations. By accomplishing a twofold demarcation – institutional (through a diploma-sanctioned instruction) as well as cognitive, theorizing animal knowledge and defining their own vocabulary – the elite veterinarians who were close to physicians and surgeons benefited from the capacity to experiment on animal bodies to develop their own anatomo-pathological, physiological, clinical and bacteriological knowledge. Throughout the process, the veterinarians constructed the problem of contagious animal diseases as a stake in which their knowledge and know-how were used to produce expertise that could be the basis for designing ways of managing these diseases and would lead to the obtention of their first monopoly on the control of contagion.