[200 years of history of National clinic of internal diseases: issues of periodization (stages 1-3)].

The main development of the clinical internal medicine in Russia took place over the past 200 years. To understand the pattern of this process, we explored its possible subdivision into phases (periods). This article presents the first part of the proposed periodization describing the characteristics and time frame of the first three stages (from the beginning of the 19th century to the late 1910s).