In New Spain, the professionalization of medicine followed the same pattern as in Europe and was prompted by similar intellectual and political factors. As with their European colleagues, the local medical elite of the late eighteenth century was greatly influenced by the Enlightenment, working tirelessly to advance medical science and improve the quality of treatment available to the public. Scientific developments in Europe influenced practitioners in New Spain through local and imported publications as well as through the arrival of a large number of European practitioners. While the Enlightenment played an important role from the scientific and medical points of view, international politics proved crucial to the development of surgery and its rapid rise to a professional level. The intense rivalry among nations prompted Spain to reorganize its armies and consequently, to turn its attention to military surgery. In Mexico, the establishment of formal surgical education and the reorganization of the armies resulted in the arrival of foreign practitioners and the creation of a two tiered system based on nationality. Of equal importance for the initial stages of professionalization was the rapid erosion of traditional social values in the late colonial period. As reflected by the increasing laxity in the enforcement of the limpieza de sangre requirements, race and ancestry as a measure of status were beginning to give way to personal merit. The medical professional gives a unique opportunity to analyze the fascinating world of late colonial Mexico. The hierarchical organization of the profession reflects contemporary society and offers a glance at daily life from the point of view of various socio-economic levels while the relations among its members mirror the complicated relations among the different segments of society. The growing criollo nationalism becomes patent in the attitude of some practitioners, an echo of future and more profound antagonism. From an intellectual point of view, the medical profession illustrates the achievements of local practitioners and pharmacists which have been largely ignored by scholars. Finally, it reflects the last efforts of Spain to reassert control over its colony and its powerlessness to stop the tide of history.