This study is based on a remarkable series of a dozen or so Latin surgical treatises composed in the period 1240-1315. In this self-conscious tradition, beginning in northern Italy and spreading to Paris, we can trace the evolution of what the writers thought of as a "science" of surgery. They insisted that they were not simply second-class manual operators, and argued that, like the new academic physicians of the thirteenth century, they could offer "scientific" reasons for what they did, and could teach their subject through books and words, not just empirical practices. They gave their craft a new rational mode of presentation, they couched their practice in theoretical terms, and thereby they made innovations in what they did and how they did it: they enlarged the scope of their activities, moving into the sphere of internal medicine, and pioneered the use of new remedies and techniques. By the end of the century they were so bold as to hope that their subject might come to be taught in medical faculties. Their vision was realized to only a limited extent, but their wider model of a rational surgery continued to be influential long after the Middle Ages.