PRACTICAL APPLICATIONS 321 



two hours, and if the reaction is positive, a whitish ring makes its appear- 

 ance at the point of contact of the two serums, the controls remaining 

 negative. According to Citron, this ring test is also evident in the pres- 

 ence of scarlet fever, measles, and syphilis. 



Precipitin Reaction in Pneumonia. Dochez and Avery have demon- 

 strated the presence of a soluble pneumococcus substance specific for 

 the type strain in the blood and urine of persons suffereng with pneu- 

 monia, and found a precipitin reaction of value in the diagnosis of the 

 type of pneumococcus causing the infection. Equal parts (0.5 to 1.0 c.c.) 

 of fresh clear serum or urine are mixed in small clean test-tubes with 

 antipneumococcus sera I and II; a distinct cloud which becomes more 

 definite after standing an hour develops with the immune serum corre- 

 sponding to the type strain of infection if due to types I or II. If the 

 reactions are indefinite they should be repeated with the immune sera 

 diluted 1 : 2 with normal salt solution. 



Blake has found a precipitable substance in the peritoneal exudate 

 of mice used in the differentiation of pneumococci by the agglutination 

 method (see page 308). After securing the exudate it is thoroughly 

 centrifuged, and equal parts (0.5 c.c.) of the clear supernatant fluid and 

 antipneumococcus sera belonging to types I and II mixed in small clean 

 test-tubes. The development of a ring or distinct cloud indicates the 

 type of infection if belonging to types I or II, and the method saves 

 time as compared with the agglutination test. 



Steinfield, working in my laboratory, has been able to confirm the 

 work of Dochez, Avery and Blake, and the practical value of these tests. 



FLOCCULE-FORMING REACTIONS 



Fornet Ring Test. Owing to the wonderful activity that has marked 

 the research work of syphilis several precipitation tests for diagnostic 

 purposes were devised. These have all been overshadowed and forsaken 

 for the Wassermann complement-fixation test. Fornet applied his ring 

 test, using the serum of patients with manifest luetic symptoms as the 

 precipitinogen, and the serum of paretics as the precipitating or immune 

 serum. Klausner advocated a simple test consisting of mixing in a small 

 test-tube 0.2 c.c. of fresh, active, and absolutely clear serum, with 0.6 

 c.c. of distilled water. This serum and the control mixtures are allowed 

 to stand at room temperature for from seven to fifteen hours, when a 

 thick, flocculent precipitate of fibrin globulin will appear at the bottom 

 of the tube. 



Porges-Meier Reaction. Forges and Meier observed that luetic 

 21 



