CYTOLYSINS 147 



no simpler means available, the Pfeiffer phenomenon might well serve 

 as a laboratory method of identifying cultures of the bacteria. 



Wright's Method for Bacteriolysis. In the course of subsequent 

 studies, other methods of investigation of bacteriolysis have been de- 

 vised, those of Wright, of Neisser and Wechsberg and of Buxton de- 

 serving especial mention. Wright exercised his usual ingenuity in 

 attacking this problem and devised two methods, one by dilution of 

 serum and the other by dilution of the culture of organisms. For the 

 collection of serum he used the Wright pipette such as is employed 

 for determining opsonic content of serum. The serum was diluted 

 with different amounts of bouillon. The culture was mixed with 

 melted gelatine and to measured amounts of this mixture was added 

 the proper amount O'f serum dilution. The final mixtures were incu- 

 bated in capillary pipettes for two to three days at 22 C, then placed 

 under low magnification of the microscope and the number of colonies 

 in the pipettes determined. In the second method the culture was 

 diluted in varying amounts of broth by means of a specially con- 

 structed capillary pipette and the suspension blown into a watch glass. 

 The culture dilutions were mixed with a standard amount of serum 

 and incubated in special pipettes. If the serum was insufficient to kill 

 all the organisms, there was bacterial growth, and the medium became 

 cloudy. Having, by previous plating, determined the number of organ- 

 isms in a given bulk of broth culture, it was possible to determine how 

 many organisms could be killed by the standard amount of serum. 

 The outlines of these methods are given because of the ingenuity dis- 

 played and the exact information gained, although at the present time 

 they are not extensively employed. 



The Neisser- Wechsberg Phenomenon. The Neisser and Wechs- 

 berg method was described almost contemporaneously with that of 

 Wright. They mixed inactivated serum dilutions in test tubes with 

 either broth cultures or salt solution suspensions of organisms, added 

 complement and incubated. Definite amounts of these mixtures were 

 added to melted solid culture media, such as agar, and plates poured. 

 After incubation of the plates, the colonies were counted and the bacte- 

 riolytic activity of the serum thus determined. A protocol taken from 

 the studies of Neisser and Wechsberg will serve to illustrate the method. 



