3o6 READINGS IN BIOLOGICAL SCIENCE 



garments. The physician to Pope Clement attributed the disease to poison- 

 ing. The idea that syphilis was a venereal form of leprosy was frequently 

 brought forward. 



In 1905 Schaudinn and Hofmann found the organism of syphilis "swim- 

 ming in the blood." It is known today that the symptoms of syphilis are 

 due to these organisms. The search for the organism of syphilis started 

 when bacteria were discovered by Pasteur to be a cause of disease — a little 

 more than half a century ago. The organisms causing the infectious diseases 

 were discovered in rapid succession, but that of syphilis stayed hidden. 

 Metchnikoff failed to find it but in 1903 he demonstrated that syphilis 

 could be transmitted to the higher apes. This discovery furnished a means 

 for studying the disease experimentally. The higher apes are the only ani- 

 mals which, when inoculated, develop syphilis resembling the disease in 

 man. The fact that calves cannot acquire syphilis is of more than passing in- 

 terest, for the opponents of vaccination have on occasion talked of "bovine 

 syphilis" which they claim is transmitted by vaccination. 



The organism of syphilis could not be made visible under the microscope 

 by means of staining. Most bacteria absorb dyes readily and the color 

 thus imparted to them allows them to be differentiated from the material 

 containing them. The organism of syphilis does not absorb dyes, but re- 

 mains colorless and transparent and hence invisible under the microscope 

 as it is ordinarily used. Two German investigators, Schaudinn and Hof- 

 mann, working at the University of Berlin in 1905, sought for the elusive 

 organism by another method of using the microscope. They used what is 

 known as dark stage illumination. Schaudinn and Hofmann placed a black 

 background under the microscope to cut off all light coming through 

 the material they were examining. They moved their source of illlumina- 

 tion to one side and brought its beams horizontally across the field. With 

 the light thus shining in a direction at a right angle to that in which they 

 were looking they could see only such light as was reflected from objects 

 which the rays struck. Under this method of examination the organism 

 of syphilis could be seen. It was a spirochete, that is, an organism spirally 

 shaped. It was, in fact, like a very tiny but a very perfect corkscrew, usually 

 with fourteen turns. The organism was named Spirochaeta pallida (now 

 called Trepone?Ha pallidimi) . 



The Spirochaeta pallida is a frail organism. It has a relatively short life 

 outside the body; under ordinary circumstances it dies in less than six 

 hours. Moreover soap and water serve to destroy spirochetes that may be 

 deposited on such articles as drinking-glasses. If the spirochete had the 

 resistance of the tubercle bacillus, syphilis would be a vastly more preva- 

 lent disease than it is. The spirochete is passed from the syphilitic only 

 during those stages of the disease when there are sores on the skin or mucous 

 membranes, but as such sores, particularly on the mouth and lips, may be 



