PRECIPITIN TESTS IN SYPHILIS 465 



cubic centimeter gives unsatisfactory results and one cubic cen- 

 timeter quantities should be used for inactivation whenever pos- 

 sible. 



Test. — A mixture of two-tenths cubic centimeter of suspension 

 and an equal volume of inactivated serum is shaken three minutes 

 in a Kahn shaking machine. One c.c. of saline solution is added. 

 Particles can be oljserved in tlie strong positive tests, while the 

 doubtful positives can be read by means of the agglutinoscope. 

 After standing twenty-four hours, it can be read as a clarification 

 reaction. An alternative method of reading is microscopic exam- 

 ination (eighty diameters magnification) of the mixture for clump- 

 ing before addition of the final saline solution. 



Advocates of the test claim specificity and sensitivity equal to 

 the Kahn over which it has no apparent advantage. The dis- 

 advantage of the test is the lack of quantitative data as to reagin 

 titer of the positive serum. 



Bruck's Nitric Acid Reaction. — Bruck (1917) precipitated 

 serum with nitric acid. The precipitate formed in syphilitic 

 serum was less soluble in dilute nitric acid than that of nor- 

 mal serum. Its agreement with complement fixation methods was 

 about 70 per cent. The reaction appears to have little practical 

 application. 



Formol Reaction. — Gate and Papacostas (1920) reported that 

 two drops of commercial formalin added to syphilitic serum pro- 

 duced a solid gel in 24 hours. Normal serum was unchanged. 

 In their paper, they claim 85 per cent agreement with comple- 

 ment fixation test. Ecker (1921), Pauzat (1920) and others re- 

 port the tast as giving inconsistent results. 



Sachs-Georgi Reaction. — Sachs-Georgi (1920) reaction is a floc- 

 culation test using a cliolesterolized lipoid antigen from beef heart. 

 A precipitate forms in syphilitic serum which does not appear in 

 normal serum under the conditions of testing. 



Vernes. — Vernes' reaction is based on the difference in turbidity 

 produced by colloidal substances. Colloidal ferric hydroxide, along 

 with other inorganic colloids, will produce greater flocculation in 

 syphilitic than in normal serum. 



Eagle Flocculation Test. — Eagle (1932, 1940) has described a 

 new flocculation test for syphilis claiming a greater sensitivity than 



