286 INFECTION AND IMMUNITY 



to one hundred cells are usually counted and an average is taken. 

 This average number of bacteria in such leucocytes is spoken of ajs the 

 "phagocytic index." The phagocytic index of the tested serum, divided 

 by that of the "normal pool" (control) serum, gives the "opsonic 

 index." 



Another method of estimating the opsonic content of a given blood 

 serum has been contributed by Simon, Lamar, and Bispham. 1 These 

 authors employed dilutions both of the patient's serum and of normal 

 serum ranging from one in ten to one in one hundred. With these 

 dilutions, they carry out opsonic experiments with bacterial emulsions 

 and washed leucocytes in the same way as this is done in the Wright 

 method, except that they recommend the employment of thinner bac- 

 terial emulsions than are usually employed in the former method. In 

 examining their slides, they do not estimate the number of bacteria 

 found within the leucocytes, but rather the percentage of leucocytes 

 which actually take part in the phagocytic process, 2 i.e., which con- 

 tain bacteria. 



By the same method of dilution, they determine what they have 

 called "the opsonic coefficient of extinction," a phrase which is used to 

 express the degree of dilution of the serum at which no further phagocy- 

 tosis takes place. They claim for their methods the more delicate de- 

 termination of variations in opsonic power. The method has not been 

 sufficiently used to permit the expression of an opinion as to its value. 



The Vaccine Therapy of Wright. In connection with his more 

 theoretical work upon opsonins, Wright has laid much stress upon the 

 value of active immunization in the treatment of. infectious diseases. 

 Beginning his work with staphylococcus and tubercle-bacillus infections, 

 he has extended his methods, with the aid of many collaborators, to 

 gonococcus, streptococcus, pneumococcus, and a number of other 

 bacterial infections. In all these cases, when possible, he uses for 

 therapeutic purposes a so-called "autogenous vaccine" which is made 

 with the bacteria isolated from the patient himself. In the case of 

 tubercle-bacillus infections, he uses for treatment the new-tuberculin- 

 bacillary-emulsion of Koch. The production of vaccine is, according 

 to Wright, as follows: 



Production of Vaccines. After isolation of the organisms from the 

 patient, cultures are made with a view of obtaining considerable amounts 



1 Simon, Lamar, and Bispham, Jour. Exp. Med., viii, 1906. 

 a Simon and Lamar, Johns Hopkins Hosp. Bull., xvii, 1906. 



