“…Historical Observations From time to time there have appeared excellent papers on the subject of relapse and re-infection in syphilis, many of them reviewing the subject historically and bringing up to date our knowledge ofexperimental syphilis. Among them may be mentioned those of Hutchinson (1895a), Chesney (1927Chesney ( , 1930, Halley and Wassermann (1928), Harrison (1929), Stokes, Schoch, and Ireland (1931), Moore (1945), Beerman (1946), Urbach and Beerman (1947), Gueft and Rosahn (mouse syphilis) (1948), and Magnuson and his colleagues (1948). This historical section has been compiled by reference to these papers and the reader is referred to them for further information on experimental syphilis, a resume of which, largely taken from Harrison (1929), is given below in a later section.…”