REACTIONS DEPENDING UPON COMPLEMENT FIXATION 313 



of the glass bulb within the rubber connection is then pinched off, 

 when the bulb fills itself automatically within a minute. The stylet 

 is returned to the needle, the outer tube replaced, fastened with a 

 strip of adhesive plaster upon which the patient's name or number 

 is marked. Thus prepared the specimen is of course sterile, and 

 may be kept for a number of days before the examination is con- 

 ducted. The serum separates out during the contraction of the clot, 

 and may be finally increased by centrifugation. 



A normal serum and a specimen from a known case of syphilis 

 should always be available as controls. 



It is recommended that all sera should be examined on the day on 

 which they have been procured. This no doubt is a good rule, but 

 I have found that fixing sera remain active for several weeks. It is 

 thus perfectly feasible to send specimens from a distance, especially 

 if the serum is separated from the corpuscles after bleeding the 

 patient. 



As human serum frequently contains amboceptors which are 

 hemolytic for sheep corpuscles in the presence of complement, arid 

 as their amount is variable and at times not inconsiderable, a factor 

 is here introduced into the experiment which could convert a positive 

 into a negative result. For we must bear in mind that the activity 

 of amboceptor and complement stand in an inverse proportion to 

 one another, such that a small amount of complement would be 

 quite sufficient to effect a very considerable degree of hemolysis, 

 if amboceptor were present in excess. 



Some investigators, such as Noguchi, have accordingly recom- 

 mended the use of an antihuman instead of an antisheep hemolytic 

 system. I have found, however, that this is not only inconvenient, 

 but also unnecessary, as the natural antisheep amboceptor can be 

 readily removed by merely diluting the inactivated serum of the 

 patient with five times its volume of the corpuscle emulsion, and 

 incubating the mixture for thirty minutes in the water-bath at 

 37 C.; the corpuscles with the anchored "natural" antisheep ambo- 

 ceptor are then thrown down with the centrifuge, when the super- 

 natant, now already diluted, serum is ready for use. This step is 

 now carried out as a matter of routine in my laboratories, and 

 assures perfectly satisfactory results. With the use of this modi- 

 fication the objectionable "Nachlosung" (continuing hemolysis 



