Who are the figures in the cartoon ? who or what do the figures usually represent? what special meaning do they seem to have in this cartoon?

Figures are Uncle Sam and Lady Liberty

Uncle Sam represents the county or the government whereas Lady Liberty represents the ideals of freedom and refugee that the US included in their founding documents.

This cartoon is regarding McCarthyism suggesting everyone is being labeled a threat to the country. The last line of the cartoon says "sometimes I even think thee" suggesting even the highest rules of the country may be violating the safety of the country.

the enslaved people onboard suffered from illness with some frequency

b. 155 enlisted men and no officers