Il8 PHARMACEUTICAL BACTERIOLOGY. 



have not yet been satisfactorily demonstrated, but Metchnikoff considers 

 their function to be that of acting upon the phagocytes in such a manner as to 

 stimulate them to perform phagocytosis. Wright, Hektoen, Neufeld and 

 others have demonstrated beyond doubt, the presence in the blood of 

 substances which act upon the infecting bacteria and get them ready fpr 

 the completion of their destruction by the phagocytes. To these bodies 

 he has given the name "opsonins" (Latin, opsono, I prepare for). That 

 opsonins are not formed in the blood is certain. Experimental evidence 

 seems to prove that they are products of muscular or subcutaneous cellular 

 activity. It is probable that the actual formation of opsonin occurs in 

 the muscle tissues and passes thence to the blood. Wright has demon- 

 strated more or less satisfactorily the presence of opsonins in the blood 

 of animals and humans and by a special technic has measured the relative 

 amount. This measurement is a ratio of the activity of the phagocytes in 

 normal blood and of that in disease, before and after stimulation, determined 

 by the number of bacteria that a single phagocyte will ingest the so- 

 called opsonic index. This index or ratio is made intelligible by decimal 

 figures representing the number of bacteria which the average phagocyte 

 will take up. We may assume that one phagocyte in normal blood will 

 ingest an average of 10 bacteria, represented in the index by the figures i.o, 

 but in disease (chronic) the phagocytes may only take up an average of 3, 6, 

 or other numbers, represented by the figures 0.3, 0.6, etc. After stimulation 

 the phagocytes may take up 15, 25, or even numbers of bacteria represented 

 in the index by the figures 1.5, 2.5, etc. 



Taking the opsonic index of an individual's blood calls for considerable 

 delicate technic. In brief, it is performed by mixing together equal vol- 

 ume quantities (measured in a capillary tube) of blood serum and an emulsion 

 of bacteria and incubating for 15 minutes at 37.5 C. Then making a thin 

 smear of the mixture on a microscope slide, drying and staining, and count- 

 ing the number of bacteria enclosed in each white blood-corpuscle (50 to 200 

 cells counted) and striking an average. This average is the index stated 

 by a decimal figure. The index thus obtained indicates the relative 

 phagocytic power of the individual's blood tested, whether below or above 

 the normal. 



The opsonic index taken in the various chronic forms of bacterial infec- 

 tions is invariably below normal and shows that the phagocytic power is 

 low, and it seems to prove that the chronicity is due to the abnormal phago- 

 cytosis. The injection of several millions of devitalized bacteria of the 

 kind causing the infection, induces the formation of the specific opsonin, 

 arouses the phagocytic activity and corrects the pathologic condition. 

 The opsonic method of treatment has been extensively tested through 

 the use of specifically active bacterial suspensions (vaccines, bacterins or 



