From Fleck's Genesis and Development of a Scientific Fact:
It's as if we wanted to record in writing the natural course of an
excited conversation among several persons all speaking
simultaneously among themselves and each clamoring to make himself
heard, yet which nevertheless permitted a consensus to
crystallize. The continuity in time of the line of thought already
mapped out must continually be interrupted to introduce other
lines. The main line of development often must be held in abeyance
to explicate connections. Moreover, a great deal has to be
ommitted to preserve the idealized main line. Instead of a
description of dynamic interactions, one is left with a more or
less artificial scheme.
Plotting the "natural course" of such a conversation might be useful for visual analysis. The "artificial scheme" can be plotted as a timeline of term frequencies.
A search for syphilis in PubMed yields 33,659 citations, spanning years 1817 to 2016.
MeSH terms are extracted from each citation, when they were available, or keywords are chosen from the title or abstract using Pattern, a natural language processor.