I'm a little bit convinced that Helen talked Gregory into taking some himself, actually. Or he did it on the sly when he was hiding it. Because otherwise I'm not sure how a person goes from missing in 1892, to prisoner of the Cabal in 2008, to Hollow Earth by 2010. Actually, of all of them, Gregory's timeline is probably the most screwed up! ;)

I wrote a fic (http://grav-ity.livejournal.com/1200804.html) about them all taking the source blood at once mostly off of Nigel's line about wanting to see what it did to Nikola.