190 THE PRINCIPLES OF IMMUNOLOGY 



organs, particularly when prepared by alcoholic extraction appear to 

 be distinctly more dependable than treponema extracts in the reaction 

 of complement fixation. The exact nature of the substances in the 

 alcoholic and in the acetone insoluble extracts is not definitely known 

 except that lecithin constitutes a large part and that it is associated 

 probably with other lipoids of the diaminophosphatid group, unsat- 

 urated fatty acids and certain proteins or protein fractions. That 

 physical conditions are of importance has been known since Wasser- 

 mann's early work, for it is established that a certain degree of turbidity 

 of the antigen or its dilutions is necessary. The watery extracts are in 

 a state of finely-suspended colloidal emulsion and, as Reudiger and 

 others have pointed out, the dilutions of the alcoholic or acetone insol- 

 uble extracts by means of salt solution can be demonstrated to have an 

 optimal degree of turbidity. 



The Syphilitic "Amboceptor." This is contained in the blood 

 serum, the cerebro-spinal fluid and other juices of syphilitic patients and 

 experimental animals. In the usual technic the blood serum is inac- 

 tivated for one-half to one hour at 56 C. in order to remove comple- 

 ment, but in certain modifications of the test the serum is used fresh in 

 order to utilize human complement in the reaction. Bronfenbrenner, 

 Reudiger and others have shown that inactivation of the serum reduces 

 its fixing power. Bronfenbrenner recommends the use of unheated 

 serum because of the greater delicacy of the reaction. In this way it is 

 possible to use for the test 0.04 c.c. or 0.05 c.c. serum, instead of the 

 usual o.i c.c. With such small amounts of serum the human comple- 

 ment is a negligible factor. Long preservation or excessive heating 

 of the serum may render it anti-lytic or anti-complementary. Con- 

 tamination from unclean skin and glassware may make it either anti- 

 lytic or lytic. The ingestion of alcohol, the presence of bile in the 

 blood in jaundice or fat in the blood after a heavy meal or in cases 

 of lipemia may all interfere with the activity of the fixing body in a 

 syphilitic serum; sera in lipemia may be markedly anti-comple- 

 mentary. There has been much discussion of the fact that human 

 serum may contain natural hemolysins for sheep corpuscles. In such 

 an instance the corpuscles may be dissolved by the excess of ambo- 

 ceptors in spite of slight fixation of complement by the syphilitic ambo- 

 ceptor, thus transforming a weakly positive into a negative reaction. 

 Sasano has found, however, that the use of an excess of immune 

 hemolytic amboceptor, for example, ten to twenty units and one and one- 

 half units of complement, determined by careful titration does not influ- 

 ence the result. Thus the factor of hemolysis by the normal anti-sheep 

 amboceptor of human serum, which amboceptor is practically never pres- 

 ent to the extent of more than four units, is practically negligible. 



The serum may be preserved for a considerable time if kept cool and 

 in sealed ampoules or in tightly-stoppered bottles. Reudiger has found 

 that mixing equal parts of fresh inactivated serum and pure sterile 

 glycerol preserves the so-called syphilitic antibody for as much as 

 two years. Under these circumstances the sera may become anti- 



