Testing an African Slave For Sickness

From an engraving entitled An Englishman Tastes the Sweat of an African, numbered from right to left the image shows Africans displayed for sale in a public market, an African being examined before purchase, an Englishman licking sweat from the African's chin to test whether he is sick with a tropical disease (a sick slave would quickly infect the rest of the 'human cargo' on a tightly packed slave ship), and an African slave wearing an iron slave marker.