LYSINS, AGGLUTININS, PRECIPITINS, ETC. 245 



Other Facts Concerning Complement. Muir and Browning have 

 shown that, on the nitration of serum, amboceptor or immune body 

 will pass through the filter, whereas alexin or complement is held back. 



This retention of complement by filters occurs only when new filters 

 are used, and it is our opinion that this is probably due to absorption 

 or complement by the finely divided substances which make up the 

 filter and not due to retention because of the large size of the comple- 

 ment molecule. 



Complement can be inactivated by shaking as well as by heat when 

 diluted 1 : 10 and shaken for about 20 minutes in salt solution. Ac- 

 cording to Gramenitski it is spontaneously partially reactivated on 

 standing. 



Complement is dependent upon the total volume of the mixture in 

 which it acts, i.e., upon concentration, the same actual quantity of 

 complement acting more strongly in higher than in lower concentrations, 

 this not being true of amboceptor or sensitizer which acts in direct 

 proportion to its actual quantity independent of the concentration. 



Complement is inhibited by hypertonic salt solution and can be 

 preserved in 15-25 per cent salt concentration for weeks in the icebox, 

 resuming its activity when diluted to isotonicity with distilled water. 

 Removal of salt by dialysis or other means of globulin precipitation 

 divides the complement into two fractions, the globulin fraction and 

 the albumin fraction, neither of which will act alone, but which to- 

 gether possess the properties of undivided complement. The globulin 

 fraction attaches directly to the sensitized cells and is therefore spoken 

 of by German investigators as "mid-piece." The albumin fraction 

 acts upon the sensitized cells only after attachment of the globulin 

 fraction and is therefore spoken of as "end-piece." 



The Fixation of Complement by Precipitates. It has been found by 

 Gengou l and confirmed by Moreschi, Gay, 2 and others, that when the 

 serum of an animal immunized with the serum of another species or 

 with a foreign albumin is mixed with a solution of the substance used 

 in the immunization, the precipitate formed will remove complement 

 from the mixture. In other words, precipitates formed by the reaction 

 of precipitin with its antigen will fix complement. This is of great im- 

 portance in complement-fixation tests; for because of insufficient wash- 

 ing, the blood cells used in producing the hemolytic amboceptor, may, 

 from the presence of serum, give rise to a precipitin as well as a hemo- 



1 Gengou, Ann. Past., 1902. 2 Gay, Cent, f . Bakt., I, xxix, 1905. 



