68 PROPERTIES OF H^EMOLYTIC SERA 



the serum is rendered practically devoid of haemolytic action ; 

 sometimes there remains a trace of complement which be- 

 comes evident when relatively large quantities are used, as 

 is the case when it is employed as the medium of suspension 

 of corpuscles. To get it entirely free of hsemolytic action 

 we heat it for an hour at 55 C. ; the small amount of com- 

 plementoid which may thus remain does not interfere with 

 the test. We shall speak of the serum thus freed of com- 

 plement as ' treated serum ', while serum heated at 55 C. 

 will be designated ' serum 55 '. In addition to the method 

 described we have also used, to take up the complement from 

 the serum, red corpuscles combined with immune-body 

 and freed from fluid. In this case, of course, the corpuscles 

 when added to the serum undergo lysis, but by adopting 

 certain procedures the haemoglobin-stained serum can still 

 be used as a medium of suspension. In other experiments we 

 employed an emulsion of kidney cells along with the corres- 

 ponding immune-body, the cells being afterwards removed 

 by centrifugalization. All the results obtained have been 

 of the same nature ; but as the first-mentioned method is the 

 most satisfactory we need give details only with regard to it. 

 In estimating the haemolytic dose of complement in the 

 ' treated serum ' we used in each tube the corpuscles of 

 0-5 c.c. suspension, and of course 0- 5 c.c. of serum was added 

 after the salt solution had been removed by centrifugalization, 



Doses of three samples of Guinea-pig's Complement in different 

 Media of Suspension for the Corpuscles of 0-5 c.c. Suspension. 



0-85 per cent. 



sod. chloride. Serum 55. Treated Serum. 



0-005 0-03 (6 D) 0-01 (2 D) 



0-0125 0-06 (5 D) 0-02 (1-6 D) 



0-004 0-1 (25 D) 1 0-015 (3-75D) 



It thus appears that the dose of complement is very much 

 smaller when the medium of suspension is treated guinea- 



1 This was by far the largest dose observed in any of our experiments 

 and must be regarded as exceptional 



