TECHNIC OF BACTERIOLYTIC TESTS 377 



In the foregoing experiment the immune serum used was several 

 weeks old; perfectly fresh serums are not so likely to show this so-called 

 " deflection of complement." In many instances, and especially if a 

 fresh serum is used, one cannot help thinking that agglutinins may be 

 responsible for the absence or diminution of bactericidal activity in the 

 lower dilutions. It is certainly true that hemagglutinins considerably 

 inhibit hemolysis, and this is especially the case with serums of low hemo- 

 lytic activity. With more potent serums the agglutinins are diluted 

 until activity ceases and hemolysis is ready and complete. Reasoning 

 from analogy, therefore, the absence or diminution of bactericidal ac- 

 tivity may be due to agglutinins, and the theory of " deflection of com- 

 plements" may be emphasized a little too strongly. 



According to Halm, normal human serums show bactericidal activity 

 in only about one-third of the cases, and the titer is only very exception- 

 ally demonstrable in dilutions higher than 1 : 500. The serums of ad- 

 vanced cases of typhoid fever or of those but recently recovered are 

 bactericidal in dilutions greater than 1 : 1000, and may reach 1 : 50,000 

 or higher. Similarly after typhoid immunization the patient's serum 

 may show a high bactericidal titer. Weston has found such serums 

 active in dilutions of 1 : 20,000, higher dilutions not being used. 



Besides being used in typhoid, the plate culture method has been 

 employed for experimental purposes in cholera, dysentery, paratyphoid, 

 and other infections with bacilli of the typhoid-colon group. With 

 these, however, the test possesses but little diagnostic significance. 



The bactericidal titer does not run strictly parallel with the agglu- 

 tinins or complement-fixing bodies. 



Measuring the Bactericidal Power of the Blood by Capillary Pipet 

 Method (After Wright). 1 By this technic it is sought to overcome the 

 fallacies of the "loopful" method of measurement and those due to 

 agglutination of the test organism. 



The native complements of the patient's own serum are used; hence 

 the serums used in this technic must be fresh. Quantitative titration is 

 accomplished by furnishing varying dilutions of culture, with a constant 

 quantity of serum. A series of volumes of serum is taken, and to these 

 are added equal quantities of progressively increasing dilutions of a 

 counted bacterial culture. The mixtures are kept at 37 C., for twenty- 

 four hours, after which each is introduced into nutrient broth and culti- 

 vated to see whether a complete bactericidal effect has been exerted. 



1 Wright, A. E.: Technique of the Teat and Capillary Glass Tube, 1912, Lon- 

 don, Constable & Co. 



