Problem:

Say a sophiscated scientist in the 19th century noted that applying soy sauce on a dead octopus leads to movement of the legs, as a result of the voltage differences resulting from the salt in the soy sauce.

Required:

Question: Is there a way for that scientist to prove, using only the methodologies available at that time, that the decapitated octopusdoesn't regain the functions that a octopus brain normally has, for even a few seconds, when the soy sauce is applied?

Please explain those methodologies.