136 Immunity 



quantities of both factors involved i.e., amboceptor and com- 

 plement. For the usual bacteriolytic investigations it is, therefore, 

 necessary to consider three factors : i , The bacteria to be destroyed ; 

 2, the serum furnishing the complement; and 3, the serum furnish- 

 ing the immune body. 



Technic. i. The bacteria to be destroyed should be prepared in the form of a 

 homogeneous suspension in physiological salt solution, similar to that employed 

 for making the agglutination tests (q. i>.). It is best to use the surface growths 

 from agar-agar, well -rubbed upon the side of a test-tube containing the fluid, 

 which is permitted to contact with the mass from time to time by inclining the 

 tube so that the fluid is able to carry away the bacteria as they are distributed. 



If quantitative estimations are to be made, the number of bacteria in the sus- 

 pension must be known or at least a standard quantity must be employed, 

 as the destructive process is a chemical one, in which the destructive agents are 

 themselves used up. 



2. The serum furnishing the complement is a normal serum that is, the 

 serum from a healthy animal that has undergone no manipulation. The guinea- 

 pig is the animal preferred. 



3. The serum containing the amboceptor or the immune body is obtained 

 from an animal that has been given a high degree of immunization against the 

 bacterium to be destroyed or dissolved. The complement contained in this 

 serum should be destroyed by heating for a short time to 55C. 



These three having been prepared, an appropriate quantity of the bacterial 

 suspension is placed in a small test-tube, and an appropriate quantity of the 

 diluted normal serum added. To this mixture of two constants, varying quanti- 

 ties of the immune serum are added and the tube stood away for twenty-four 

 hours on ice. In almost every case it will be found that the immune serum con- 

 tains a great quantity of agglutinating substance, so that the bacteria all fall to 

 the bottom in a short time. This is independent of bacteriolysis. The bacterial 

 destruction is gauged by the disappearance of the bacteria or by their failure to 

 grow when transplanted to appropriate culture media. 



By making the bacterial suspension and complementary serum constant quan- 

 tities (taking care that not too many bacteria be present), one is able to estimate 

 the value of the immune serum. By using the bacterial suspension and a heated 

 immune serum (containing no complement) as constants and varying the addi- 

 tion of complementary serum, one can estimate the respective values of several 

 complementary serums. By using both serums as constant factors and varying 

 the number of bacteria, one can determine the exact bacteriolytic value of the 

 mixture. By taking out and planting drops from time to time the rapidity of 

 bacteriolysis can be determined, and by plating out the drops and counting the 

 colonies one may arrive at percentages of destruction and express the bacteriolytic 

 process in the form of a curve. 



THE DEVIATION OF THE COMPLEMENT, OR THE "NEISSER-WECHSBERG 



PHENOMENON" 



A peculiar phenomenon has been observed and studied by Neisser 

 and Wechsberg.* When an animal whose blood-serum is nor- 

 mally possessed of a high degree of germicidal power is immunized 

 by repeated injections of a bacterial antigen, its serum when ex- 

 amined by the usual methods fails to show the usual increase in 

 the specific bactericidal action toward that particular organism, 

 though it retains its general bacteria-destroying power. If, however, 

 the serum be greatly diluted, its action is changed, so that it loses 

 its general bacteria-destroying power and develops marked increase 

 in the specific destructive action upon the particular bacteria used 



* "Munch, med. Wochenschrift," April 30, 1901, XLVIII, No. 13, p. 697. 



