The ocean journey of a slave from Africa to America was long and gruesome; many slaves died en route. Dehydration was a major cause. Who, Fryer wondered, is less likely to suffer from dehydration? Someone with a high degree of salt sensitivity. That is, if you are able to retain more salt, you will also retain more water—and be less likely to die during the Middle Passage. So perhaps the slave trader in the illustration wanted to find the saltier slaves in order to ensure his investment.
