132 METHODS OF EXAMINING SERUM 



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 Keaction. 

 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 spirochsetes (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 

 and Levaditi, however, found that an extract of normal guinea- 

 pig's liver along with syphilitic serum fixed complement, and 

 subsequent observations showed that extracts of other tissues are 

 also more or less efficient, as are also certain definite substances, 

 such as sodium oleate, sodium glycocholate, lecithin, mixtures 

 of such and especially mixtures of lecithin and cholesterin, etc. 

 Although abundant observations have established the validity 

 of the test as a means of diagnosis, the reaction which led to its 

 discovery is no longer sufficient to explain it, and the nature of 

 the reaction is not yet understood. 



In order to carry out the test, we require (a) serum from the 

 suspected case, (6) an extract of liver or other organ, and 

 (c) the fresh serum of an animal to act as complement. The fol- 

 lowing are the details, arranged in two stages : 



