92 PROPERTIES OF H^EMOLYTIC SERA 



for which will be given later, the observations recorded, 

 except where otherwise stated, were always made with fresh 

 filters. Even under these conditions considerable varia- 

 bility in the action of filters was found, as will be shown 

 below. We always employed a hsemolytic test for estimating 

 the amount of complement, namely, 1 c.c. of a 5 per cent, 

 suspension of ox corpuscles, sensitized with immune-body 

 from the rabbit. The haemolytic dose was in each case tested 

 before and after filtration of the serum. 



FILTRATION OF HJEMOLYTIC COMPLEMENT 



As the result of a large number of experiments, we may 

 state the general conclusion that a small quantity of serum, 

 say 3 to 4 c.c., filtered under the above conditions, loses 

 hsemolytic complement to a great extent, sometimes almost 

 completely. It will be sufficient if we give the two extreme 

 cases which we have met with : (a) In one case the dose of 

 complement before filtration was 0-006 c.c., while after 

 filtration 0-4 c.c. gave practically no lysis. We calculated 

 that in this case not more than one seven-hundredth part 

 of the complement originally present had passed through. 

 (b) In another case the dose before filtration was 0-003 c.c., 

 whilst after filtration it was 0-025 c.c. In this case the 

 amount of complement had been reduced to a little less than 

 an eighth of the original amount. It is thus seen that great 

 variations in the amount of complement retained occur, and 

 these are also met with when the same serum is filtered 

 through different filters. 



With regard to the mechanism by which the complement 

 is retained, we can say nothing further at present than that 

 in all probability it is fixed in some way in the pores of the 

 filters. It might possibly be destroyed in the process of 

 filtration, but we know of no other example of destruction 

 of complement in so short a time. There is, of course, no 

 question as to the complement molecules being mechanically 



