TITRATION OF ANTIGEN 



179 



Similarly, the luetic sera are most active when doses of 0.2 and o.i c.cm. 

 are employed. Amounts greater than 0.2 may result in an unspecific 

 reaction. The most favorable combinations are, 



0.2 c.cm. of extract + 0.2 c.cm. serum. 



o.i c.cm. of extract + o.i c.cm. serum. 

 The accompanying table presents the titration of an antigen in detail. 



a. Preliminary Test Titration of the Antigen. 



The test proves that 0.4 c.cm. of extract is not able to bind o.i c.cm. of 

 complement. That 0.8 c.cm. of lues extract causes only an incomplete 

 hemolysis, while 0.6 c.cm. produces no hemolysis whatever, is explained 

 not by its lessened tendency of binding complement, but by the greater 

 amount of hemotoxin which 0.8 c.cm. possesses. 



Keeping in mind the rule of Weil and Nakayama about the summa- 

 tion of antigen, this particular antigen will be employed in the quantities 

 of 0.2 c.cm. and o.i c.cm. (0.2 being 1/2 of 0.4 c.cm. which is the largest 

 amount that does not of itself fix complement) . 



b. Examination and titration of 4 luetic sera by Citron's method (see 

 Plate II). 



The technical details of the test are as follows: 



Three test-tubes are assigned for each test and placed in a test-tube rack. The 

 name of the patient is written upon the first of these tubes. Another rack contains one 

 tube for each patient and labelled accordingly. In addition there is an " antigen tube," 

 which is placed in the first rack at the end of all the other tubes; also a "normal 

 extract," a "system," "complement," and "blood control tube," which are placed 

 in the second rack. The amount of syphilitic antigen required for the entire work 

 is calculated as follows. For each test 0.3 of antigen is required; for five cases (in- 

 cluding controls) 1.5 c.cm. are needed + 0.4 c.cm. for the antigen control tube =1.9 

 c.cm. in all, or 2.0 c.cm. in round numbers. This amount is diluted with normal salt 

 solution in the proportion of i : 5 so that 8 c.cm. of saline are added ( 2 : 10) ; i c.cm. 

 of this dilution contains 0.2 antigen and 1/2 c.cm. contains o.i antigen. The first 

 tube (i, 4, 7, ic, etc., in diagram) of every test therefore receives i c.cm., the second 



