SPIROCHETE GROUP 453 



infection, such as fever. This may last for several years and 

 an immunity be established, which, however, may not be complete 

 enough to prevent gradual sclerosis of blood-vessel walls and de- 

 generations in the parenchymatous organs, and even the appear- 

 ance of tertiary lesions. 



Immunity. No practicable method of either active or passive 

 immunization against the disease has been developed by the use 

 of the organism or its products. 



Bacteriological Diagnosis. This may be accomplished by 

 direct examination, stained mounts, the Wassermann test, or 

 by chemical recognition of certain changes in the character and 

 composition of the blood-serum. The organisms may be observed 

 in the fluid expressed from fresh tissues by use of dark field illu- 

 mination. Smears may be prepared and stained with Giemsa's 

 stain, or tissue sections may be used. 



The Wassermann test for syphilis has already been described 

 in the discussion of fixation of complement in the section on Im- 

 munity. As an antigen, extracts from the organs of a fetus are 

 used, for in these organs the spirochetes are found in the greatest 

 numbers. The blood-serum of the suspected patient is tested 

 for its possible content of specific amboceptor with fresh guinea- 

 pig serum for complement, sheep red blood-cells, and the serum 

 from a rabbit possessing hemolytic amboceptor for these erythro- 

 cytes. The test requires considerable care and must be checked 

 at every step. It has been found in practice to give quite reliable 

 data. The test has been modified in many ways since first pro- 

 posed. 



Various substances, such as 1 per cent, solutions of lecithin, 

 sodium oleate, sodium glycocholate, and taurine have been found 

 to give more or less characteristic precipitates with the blood of 

 syphilitics. 



Transmission. The disease is transmitted usually through 

 sexual congress, rarely through infective drinking vessels, closets, 

 and by direct inoculation, as sometimes happens in surgical work. 

 The disease may be inherited : the organism may possibly enter 

 through the ovum or the sperm, or pass from the circulation of the 

 mother to that of the fetus. 



