False-colour scanning electron micrograph (SEM) showing the attachment of several anaerobic spirochaete bacteria, Treponema pallidum, to testicular cells. T. pallidium causes syphilis in man, entering the body during sexual intercourse through the mucous membranes of the vagina or urethra or through transmission from an infected pregnant woman to her unborn child (congenital syphilis). The disease passes through three stages; the third (tertiary syphilis) may cause severe damage to the heart, blood vessels, brain & spinal cord. Blindness & insanity may result. Penicillin is effective if administered in the early stages. Magnification: x8,700 at 35mm size. Attachment of T. pallidum recorded 22 hours post- infection. Published in Infect. Immunity 17:174-