Fig. 16. Treponema pallidum in smear from secretion of a 

 fresh, hard chancre. The dark spots represent the red blood- 

 cells; the light, wavy lines the spirochetes. X 1000. (After 

 Lenharts.} 



result is a general skin eruption, sore throat, fever, 

 and anemia, symptoms that develop in from six to 

 twelve weeks after the chancre, and mark the begin- 

 ning of the secondary stage. The disease is most 

 infectious at this period. Later the spirochetes be- 

 come localized in certain tissues, particularly the brain 

 and spinal cord, and lead to the formation of nodules 



DISEASES CAUSED BY PROTOZOA. 115 



chancre, which develops from three to six weeks after 

 exposure. It may be located anywhere on the body, 

 but is always at the point where infection entered. 

 The organisms are at first localized in the primary 

 sore, but very soon spread to the glands near by, and 

 then to the blood, causing a general infection. The 



