126 PROPERTIES OF HJ3MOLYTIC SERA 



2. Filtration Experiments. 



Attempts to produce complete sedimentation of the 

 receptors having thus failed, it occurred to us that it would 

 be of interest to test the effect of passing the fluid containing 

 the laked corpuscles through a porcelain filter. The question 

 simply is Are the receptors retained in the filter, or do 

 they pass through ? The methods of laking with water 

 and of lysing with haemolytic serum are exactly the same 

 as those detailed above, so they need not be repeated. 



(a) Laking with water. The red fluid, made up to a concentration 

 of 0-85 per cent, sodium chloride, is slowly passed through a sterile 

 filter ; 1 c.c. of the nitrate is placed in each of a series of tubes, and 

 as a control we have a series containing simply 1 c.c. of 0-85 per cent, 

 salt solution in each. To each tube in the two series is added several 

 doses of immune-body, and then, as before, increasing amounts of 

 complement, the amount in the first tube being less than a hsemolytic 

 dose. After two hours' incubation, the presence of complement is 

 tested for in the usual way. 



The results have varied somewhat. In some cases there 

 was no evidence that any of the receptors had passed 

 through ; that is, the filtrate had no power of taking up 

 complement when immune-body was added to it. In other 

 cases, receptors could quite easily be demonstrated in the 

 filtrate, though never in so great quantity as in the clear 

 fluid obtained by centrifugalization, even with 1-7 per cent, 

 salt solution. We may say that it is exceptional for 1 c.c. 

 of the filtrate to take up a haemolytic dose of complement, 

 excess of immune-body of course being present. We have 

 endeavoured to ascertain the reason of the variations 

 observed. As one result, we have found that when a 

 quantity of the fluid containing the laked corpuscles is 

 passed through the filter, the portion which passes through 

 first is almost free from receptors, while that passing through 



