THE WASSERMANN REACTION 631 



In hot weather, the tubes containing the complement and the 

 complement dilution prepared should be kept in iced water. It 

 is better to make up only sufficient complement dilution for the 

 work immediately in hand, and to make up more as required. 



The Wright's capsules, tubes into which the serum is pipetted, 

 and the tubes used for the test, must be scrupulously clean. 



This caution is particularly necessary as regards the quill tubes 

 used in the " small volume " technique, as they are more diffi- 

 cult to clean than larger tubes, and quill tubes with rounded 

 (not pointed) bottoms are, therefore, to be preferred, being more 

 readily cleaned. The used tubes may be placed in a bath of 

 dilute acetic acid and subsequently rinsed in several changes of 

 water, finally in distilled water and then drained and dried. 



Standardisation of Antigen 



The Mclntosh and Tildes antigen, which is recommended to 

 be used, remains remarkably constant for months at a time. 

 This or any other antigen may be standardised by the following 

 method. 



Method. Make up with saline several dilutions of the antigen 

 above and below twice that strength which would probably be used 

 for the test. Make mixtures of the saline- antigen dilutions and 

 complement (the proper dilution of the latter as determined by 

 the standardisation in saline described at p. 627), 5 vols. of each, 

 in quill tubes, incubate for twenty minutes for fixation to take 

 place. Then add 5 vols. of the amboceptor-corpuscle mixture (as 

 used for the test) and incubate for fifteen to twenty minutes. 

 Note which is the highest dilution of antigen which gives 

 complete fixation. 



The following illustrates the result that may be obtained : 



Tube 1. Dilution of Antigen 1 : 5 = No haemolysis. 

 ,,2. ,,1:6= 



31 7 

 ,, J> 5 -*- ' ~ J> 



,,4. ,, ,, 1:8= Partial haemolysis. 



,,5. 1:9= Nearly complete haemo- 



lysis. 



From this it is seen that the highest dilution of the antigen 

 which completely fixes complement is 1 in 7. For the actual test 

 the antigen is used about half this strength, viz. 1 in 14-1 in 16. 



