Street Doctor, 1877.

UNITED KINGDOM - FEBRUARY 16: Woodburytype of a man selling Couch Preventative Lozenges in the street, taken from 'Street Life in London' (1877), written by Adolphe Smith with photography by the Scottish photographer John Thomson (1837-1921). The aim of this book was stated as being: 'to bring before the public some account of the present condition of the London street folk, and to supply a series of faithful pictures of the people themselves'. It is one of the first examples of photography used as social documentary. (Photo by SSPL/Getty Images)