THE RELATION OF LIPOIDS TO IMMUNITY 561 



4. A saturated solution of barium hydroxid made equivalent to the 

 normal solution of sulphuric acid. In the use of the barium hydroxid" 

 it is imperative to prevent its exposure to the air. A solution that has 

 become cloudy, owing to the entrance of carbon dioxid, should not be 

 used. In carrying out the test it is best to pour out the amount of barium 

 hydroxid needed for the test into a rubber-stoppered bottle or test-tube, 

 so as not to contaminate the stock solution. 



5. A 1 per cent, alcoholic solution of phenolphthalein containing 1 

 per cent, of a 10 per cent, solution of strontium chlorid. The strontium 

 chlorid has been found to catalyze the reaction. 



The Test. The test is conducted as follows: A number of clean 

 beakers of about 50 c.c. capacity are used. For each dilution of the 

 serum a separate beaker is required. One beaker is used for an antigen 

 control, and another to control the system of barium hydroxid and 

 sulphuric acid. Five beakers may be used, Nos. 1, 2, and 3 constituting 

 the main test, No. 4 the antigen control, and No. 5 the system control. 



The reagents are added by means of overflow pipets. To each of the 

 first four beakers is added 1 c.c. of the dilute antigen to be used in the 

 test (about 1 : 10,000). To beaker 5 is added 1 c.c. of the salt solution 

 used in making the dilutions of the antigen and the serums. Now 0.1 

 c.c. of the dilute serum to be tested is added to each of the first three 

 beakers, each beaker, however, containing the same serum in a different 

 dilution. To beaker 5 the same quantity of salt solution is added, but 

 to beaker 4 the antigen control no serum or salt solution is added. 



To each of the five beakers the system of sulphuric acid and barium 

 hydroxid and phenolphthalein is now added carefully. First, 2 c.c. of 

 the normal suphuric acid solution are added to each; then 2 c.c. of the 

 barium hydroxid, and finally 0.1 c.c. of the phenolphthalein strontium 

 chlorid mixture. 



It will be seen that beaker 4 the antigen control contains all the 

 constituents of the test-beakers 1 to 3 except serum. To make beaker 

 4 qualitatively as well as quantitatively equal to beakers 1 to 3, 0.1 c.c. 

 of the dilute serum (the average of the dilutions of serum which are used 

 in the test) is now added to beaker 4, the reaction having already taken 

 place. 



The addition of the sulphuric acid and barium hydroxid requires 

 great care. Since the reaction depends on small differences in acidity 

 or alkalinity, it is obvious that slight errors will vitiate the results. For 

 the acid and the alkali separate pipets are used. After emptying the 



pipet of its content of acid or alkali, the last traces adhering to the 

 36 



