412 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



the power of activating a hemolytic amboceptor, and (2) fixability, or 

 the power of being " fixed" by antigen and antibody. Noguchi and 

 Bronfenbrenner have studied the complements of the dog, sheep, hog, 

 ox, rabbit, and other animals, and found that the (complement of the 

 guinea-pig was best adapted, from all standpoints, for the complement- 

 fixation testy The complements of pigs and sheep are quite fixable, but 

 their weak nemolytic action and rapid deterioration render them unsuit- 

 able for fixation purposes. Rabbit complement is quite active, but is 

 not easily fixable. Kolmer, Yui, and Tyau found rat complement 

 fairly well suited for making the syphilitic reaction with an 

 antihuman hemolytic system. 



^The hemolytic power of guinea-pig complement is not constant.) 

 In unhealthy animals it is likely to be low, and even among normal 

 animals it may show some variation. For this reason the hemolytic 

 power of each serum is determined by a method of titration before 

 complement-fixation reactions are conducted. Fixed doses of hemolysin 

 and corpuscles may be used, and the amount of complement necessary 

 for effecting complete hemolysis may be determined, or a fixed dose of 

 complement and corpuscles may be used with different amounts of 

 hemolysin, the chief object being to adjust all three factors of the hemo- 

 lytic system, namely, complement, corpuscles, and hemolysin, to exact 

 anol known proportions. 



(The complement in the serums of different guinea-pigs may show 

 considerable variation in fixability.) The amount of complement in- 

 hibited by serum alone and organic extract alone, or by given constant 

 quantities of serum and extract, may vary more markedly than their 

 complementary activity. To reduce this error to a minimum it is advis- 

 able, whenever possible, to use the pooled serums of two or more pigs 

 for making complement-fixation tests. 



Guinea-pig complement serum is collected by bleeding, the animal, 

 under ether anesthesia, into a Petri dish or centrifuge tube. The large 

 vessels on both sides of the neck are quickly severed with a pair of 

 sharp-pointed scissors or a scalpel, care being exercised not to sever the 

 trachea and esophagus. A funnel is used for collecting blood in centrifuge 

 tubes. It is well finally to sever the spinal cord, in order that the animal 

 may not recover from the anesthetic and thus insure a painless operation 

 throughout. (See p. 46.) 



It is best to keep the blood at room temperature for a few hours 

 until coagulation has occurred and the serum has separated; then place 

 the whole in the ice-chest until needed. Blood may be collected in 



