symbols of the serpent wriggled and twisted over chemical writing

An example of an extended metaphor used to describe a scientific idea:

"The wild belief in alchemy had been scotched, but the serpent still lived, for its symbols still wriggled and twisted over the pages of chemical writings. No amateur could venture alone through its labyrinthine jungles. In one Italian manuscript of the early seventeenth century by Antonio Neri, the metal mercury was represented by no less than twenty symbols and thirty-five different names! In another book, lead was designated by fourteen symbols and sixteen names."

Bernard Jaffe (1934) Crucibles. The Lives and Achievements of the Great Chemists. Jarrolds Publishers.

alchemy, while a precursor of chemistry, is based on alternative conceptions

The serpent is used here as a metaphor to represent the nature of alchemy

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