What is jessie ordered to do with rum he was told to fetch

In the story "The Slave Dancer" written by Paula Fox the main character Jessie is told to fetch rum to give to the slaves. It is said that oftentimes slaves die on board the ships during the African slave trade and that giving the slaves rum keeps them moving, dancing, and alive. Giving slaves rum thereby protecting the "cargo" or "property" that are, saving the slave trader's money.