Quotation from: Manual of Surgery

Written by: Alexander Miles and Alexis Thomson

The spirochaete may be recognised in films made by scraping the deeper
parts of the primary lesion, from papules on the skin, or from blisters
artificially raised on lesions of the skin or on the immediately
adjacent portion of healthy skin. It is readily found in the mucous
patches and condylomata of the secondary period. It is best stained by
Giemsa's method, and its recognition is greatly aided by the use of the
ultra-microscope.