The word was also sometimes used to refer specifically to the Vulcan species. (ST reference: The Worlds of the Federation) Vulcanoid races require a daily diet of Kelassium in order to avoid intestinal scarring. (TNG novel: Red Sector) In addition to this, TLTDH gas had a unique effect on them as it could produce laughter amongst them as well as feelings of exhiliration, euphoria and possibly unconsciousness amongst them. (TOS video game: 25th Anniversary)