FIXATION OF COMPLEMENT 127 



not to make ragged openings in the vein, often the simple removal 

 of the previous scab will be followed by a free blood flow. 



A worker associated with one of us has shown that this method can be 

 applied in guinea-pigs, provided these be of fair size. Here successive 

 samples of 2 c.c. can be obtained from the ear veins. 



Fixation of Complement or Complement Deviation. — From 

 the facts given above it follows that sensitised corpuscles, i.e., 

 corpuscles treated with immune-body, may be made to serve as an 

 indicator for the presence of complement. If an antibacterial 

 immune-body is present in a serum heated at 55° O, the serum 

 when added to the corresponding bacterium leads to the fixation 

 of complement, and thus prevents haemolysis when sensitised 

 corpuscles are added. If we represent the bacteria, or rather the 

 receptors in the bacteria, by X, the immune-body by anti-X, and 

 the complement by C (normal serum, say, of a guinea-pig), we may 

 represent the method of experiment by the following scheme : — 



X + anti-X + C 



+ sensitised corpuscles 



(The vertical dotted line represents a period of incubation for 

 one and a half hours at 37° C.) 



If lysis of the sensitised corpuscles does not occur after incuba- 

 tion at 37° C, then the complement has been fixed and an 

 immune-body has been shown to be present, provided that a 

 suitable control shows that the bacteria alone, without immune- 

 body, do not fix sufficient complement to interfere with lysis. 



This method has now been extensively used for demonstrating 

 the presence of immune-bodies in the blood of patients suffering 

 from a particular bacterial infection. It has also been applied 

 to determine whether a suspected bacterium is really the cause 

 of a disease, for if the bacterium gives with the serum of the 

 patient deviation of complement, then there is a strong pre- 

 sumption that it is the infective agent (vide Immunity). 



The Serum Diagnosis of Syphilis, Wassermann Reaction. — 

 Wassermann, Neisser, and Bruck, proceeding in accordance with 

 the facts established with regard to the deviation of complement, 

 tested whether a similar phenomenon might not be obtained in 

 the case of syphilis. For this purpose they mixed together a 

 watery extract of syphilitic liver, rich in spirochaetes (antigen), 

 and serum from a syphilitic case (supposed to contain anti-sub- 

 stances), and found that a relatively large amount of complement 

 was fixed. On the other hand, when the serum from a non- 

 syphilitic case was substituted for the syphilitic serum, little or 

 no fixation of complement occurred. The result was thus in 

 accordance with expectations on theoretical grounds. Marie 



