The Hemolytic Amboceptor 297 



ferments of the hving organism, salts affect it, and in salt-free media 

 its action ceases, to return when a small quantity of an alkaline salt 

 is added. Not only inorganic salts, but salts of the fatty acids and 

 the bile-salts may inhibit it. Certain lipoids, such as lecithin, 

 cholesterol, protogon and tristearin, and neutral fats' inhibit the 

 complementary action. Some of these substances are always 

 present in the serum containing the complement itself or in the other 

 serums to be tested by its use, and, as Wassermann and Citron have 

 pointed out, we really know nothing about complementary action. 

 Aleuronat, inuUn, peptone, albumose, tuberculin, natural and 

 artificial aggressins, gelatin, casein, sitosterin, coagulated serum- 

 albumin, and albuminous precipitates all act as inhibitives to com- 

 plementary action. 



Now, in all combinations of several serums and antigens it is 

 always possible that some of these complement-binding or comple- 

 ment-inhibiting substances may be present, hence the first thing that 

 has to be done in the way of titrating the antigen — which is a tissue 

 extract, rich in Upoids which inhibit complementary action — is to 

 determine how much of it can be added to the "hemolytic system" 

 without disturbing hemolysis. 



As, however, the antigen is not used by itself, but always in com- 

 bination with a serum to be tested, we must always combine it with 

 serum when making the titration, so that the requirements of the 

 test may be conformed with. In order that the essential difference 

 between the normal serum and the syphilitic serum can be reduced 

 to precise calculation it is imperative that, in all the tests, the same 

 quantity of added serum be employed. Experience has shown this 

 quantity to be 0.2 cc, and this we regard as the unii of serum to be 

 tested. 



To titrate the antigen we require (i) a normal human serum and 

 (2) a known syphiUtic serum, obtained from blood drawn from the 

 arm veins of cases known to be well and cases known to be S3^hilitic 

 respectively. These serums should be kept on hand in the labora- 

 tory in considerable quantity, as they are constantly needed for 

 making the controls that must accompany each .test, as weU as for 

 making the preliminary titration of the antigen. 



The "set-up" for the titration of antigen is fairly simple. A 

 series of tubes is prepared and divided into two groups. Into each 

 tube in each group is placed i unit of complement. Each tube of 

 one group receives the addition of 0.2 cc. of the normal serum; 

 each tube of the other group, 0.2 cc. of the known S3^hilitic 

 serum. All the tubes now receive additions of antigen, so that one 

 tube of each group contains the same quantity. The quantity of 

 antigen not being known, it is only through the experience of others 

 that we can guess where to start. An idea can be formed through 

 study of the accompanying tabulation. 



From this we find that the unit of antigen is 0.09 cc, the largest 



