378 Mr. A. H. Caulfeild. Inhibitive and Fixation [Aug. 24, 



complement, a corresponding variation will occnr in the end results of 

 antigen saline controls. Thus with increase more or less haemolysis appears 

 in the first tube ; with decrease lessened haemolysis in the second and possibly 

 the third tube. The fifth tube shows as accurately as possible the amount of 

 complement non-specifically affected by the antigenic dilution. Qualitatively 

 the most efficient extract in the antigenic titre is the one which causes the 

 greatest amount of fixation with sera containing sensitisers and, at the same 

 time allows the greatest amount of haemolysis in the fifth tube (Table I). 

 With the end results of Table I, more than one and less than two units of 

 complement are available for the specific action of inhibitive and fixative 

 sera with antigen. 



(4) Nomenclature Adopted in Beading the End Re&ults. — The need of a 

 comparatively accurate method of recording the end results has been felt by 

 all who have worked with fixation tests, and consequently a number of 

 methods have been devised by Madsen, Epstein, and others. Cloewes 

 photographs the end results ; this seems to be the most accurate, although 

 the most time-consuming method. The range of antigen and comple- 

 ment control as outlined in Table I gives one a standard for each protocol, 

 which has seemed to aid in the use of the five expressions in terms of 

 haemolysis : — 1. None (absolutely no haemolysis). 2. Almost none. 3. Some. 

 4. Almost complete. 5. Complete (absolutely complete). 



A further grading is allowed by the use o the signs + and — , which, 

 however, are probably of value only for the immediate comparison of a set 

 of tubes in the same protocol. 



(5) Effect of Age upon Antigen. — By thus controlling the antigen for each 

 protocol it has become evident that with time the anti-complementary power 

 increases in an irregular fashion. Thus Extract TV, prepared for use on 

 November 1, began to show towards the end of December tendencies towards 

 incomplete haemolysis in the third tube (0*25 c.c). By the end of January 

 this alteration had progressed so far that with two units of complement no 

 haemolysis resulted in the first three tubes of antigen control. This change 

 has occurred with most preparations, so that the full efficiency of an antigen, 

 lasts in the neighbourhood of two months. With this irregular onset of' 

 increased anti-complementary properties there is decreased efficiency for the 

 exhibition of the inhibitive reaction. This change applies in a comparable- 

 fashion as regards true fixation, if the amount of non-specific fixation by 

 antigen is taken into account. In other words, complete specific fixation 

 with two units of complement may not be produced with suitable sera, if the 

 antigenic dilution be increased and brought to compare with the amount of 

 non-specific fixation produced by the original antigenic dilution. It would 



