Continuity mistake: When the pirates attack the crow's nest where the kids are, one of them cuts his moustache with his sword. Later on his moustache grows back.
Continuity mistake: When Nana is sent outside and holds the rope, the length of the short end increases between shots.
Continuity mistake: When Mr. Darling is getting dressed, a jar of water suddenly appears no the night table behind him.
Continuity mistake: When the movie begins and Mrs. Darling grabs a hairpin, a bottle on the table disappears between shots.
Answer: They never officially confirmed; but it was likely castor oil or morphine. Both were used around this time period as a common "medicine" for children.
Cocaine, heroin, and alcohol-based elixirs were also commonplace and considered "safe and effective" for children.
raywest