IMMUNITY AND SUSCEPTIBILITY 709 



thirty minutes in order to destroy its complement and also it is necessary 

 to accurately find out the amount of guinea-pig serum which will com- 

 plement the resulting hemolytic amboceptor. This definite amount of 

 complement having been determined, it is mixed with syphilitic antigen 

 plus the syphiUtic amboceptor, mentioned above, and allowed to incu- 

 bate for one hour and thirty minutes at 37°. If the serum is from a 

 case of syphilis the antibodies (amboceptors) will be present and com- 

 bine with the antigen, and also the guinea-pig serum complement. The 

 next step in the technic is to add to the above-mentioned mixture the 

 hemolytic amboceptor and its antigen, sheep corpuscles. If the com- 

 plement has been bound there will be none left to combine with the 

 hemolytic amboceptor and no hemolysis of the sheep corpuscles will 

 result. If the patient's serum does not contain syphilitic amboceptors 

 or antibodies, the complement will not be bound and hemolysis will 

 result. This test has been designated as the Wassermann test on 

 account of the man first working it out in the case of syphilis, and has 

 shown itself to be very efficient in the diagnosis of this disease in 

 suspected cases. Many modifications of this test have beeii devised, 

 some of which are very accurate. 



The fixation of the complement may be made use of in the detection 

 of any bacterial antibody, the procedure being approximately the same 

 as above indicated and the hemolytic system used as an indicator as in 

 the case of syphiUs. The antigen, however, is different. When working 

 with specific bacteria a suspension of bacterial cells in 0.85 per cent 

 sodium chloride solution constitutes the antigen. 



Cytotoxins and Cytolysins. — The names cytotoxin and cytolysin are 

 used synonymously and are applied to those substances in serums and 

 other body fluids which have the power of destroying cells other than 

 erythrocytes. In a broad sense any substance destroying a cell would 

 be cytotoxic but the terms are usually applied in the more limited 

 manner, as above indicated. 



Cytotoxins are produced in the same manner as other antibodies. 

 The immunization of an animal, for example, with renal (kidney) cells, 

 produces in the blood serum of that animal a cytotoxin for the paren- 

 chymatous cells of the kidney. Cytotoxins can be produced for prac- 

 tically all the parenchymatous cells of the body. These immune bodies 

 are not very specific and even careful experimentation leads to confusing 

 results. For example, when an animal is immunized to kidney cells) 

 there is produced in the body of the immune animal cytotoxins for 



