In his travels in Africa, Winterbottom, physician to the Colony of Sierra Leone (now Republic of Sierra Leone) on the west coast of Africa, saw sleeping sickness, which he described in vol. 2, pp. 29-31, as a species of lethargy. He also noticed that slave-dealers would not buy slaves whose neck glands showed signs of enlargement. Digital facsimile of vol. 1 from the Internet Archive at this link;  digital facsimile of vol. 2 from the Hathi Trust at this link.;