Darkfield method

Microscopic method with centrally darkened light beam incident from the side. Application: Mainly vital diagnosis of treponema in syphilis in the irritant secretion.

The irritant serum is obtained by laterally compressing the lesion to be examined (ulcer or primary effect, weeping lesion of the secondary stage) between two fingers after cleaning with saline solution until a crystal clear secretion, the irritant secretion, emerges from the tissue. This secretion contains the spirochetes. The secretion is obtained by means of a glass capillary and is applied to a microscope slide and covered by a cover glass. The preparation can then be examined by oil immersion at 1000x magnification.