THE TECHNIQUE OF SERUM REACTIONS 



311 



an enumeration of the colonies in the various plates is made and 

 the results are compared. 



BACTERICIDAL TEST IN VITRO 



(To DETERMINE THE BACTERICIDAL POWER OF A TYPHOID IMMUNE SERUM AGAINST 



TYPHOID BACILLI). 



lib I 1.0 



1.5 c.c. NaCl + 0.5 Typh. Emulsion 

 1.5 " " +0.5 



CONTROLS 



+ 0.5 



+ 0.5 c.c. Rab. Ser. 1:15 



Plated immediately ] More than 

 after 3 hrs. \ 10,000 

 " 3 " J Colonies. 



The in vitro bactericidal tests have been employed, practically, 

 chiefly in the diagnosis of typhoid fever by Stern and Korte. 9 While 

 the serum of normal individuals shows practically no bactericidal 

 power for typhoid bacilli, the sera of typhoid patients may be ac- 

 tively bactericidal in dilutions as high as 1 :50,000. 



Protection tests in mice, etc., are described under the " standard- 

 ization" of pneumococcus and streptococcus serum in the chapters 

 dealing with these organisms. 



Hemolytic Tests. Determination of the hemolytic action of blood 

 serum, bacterial filtrates, and of a variety of other substances, such 

 as tissue extracts and animal and plant poisons, is frequently made 

 in bacteriological laboratories. Familiarity with the methods of 

 carrying out such tests is especially essential since hemolytic tests 

 are also employed in determining other serum reactions, such as 

 the "complement-fixation tests" discussed in another section. 



For these tests it is necessary to prepare washed red corpuscles 

 of the species of animal against which the hemolysins are to be 

 tested, and to obtain these, blood may be taken in one of the follow- 

 ing ways: 



A. If small quantities of blood corpuscles are desired, the blood 

 may be received into a sterile test tube into which a copper or other 

 wire bent into a loop at the lower end has been introduced. This 



9 Stern und Korte, Berl. klin. Woch., 1904. 



