QUANTITATIVE ESTIMATION OF BACTERIOTROPINS 



207 



the opsonic index has less practical significance than was originally be- 

 lieved. One point is clear, however, that the work of Wright and others 

 has broadened the field of vaccine therapy and placed it upon a firmer 



Day of 

 Month 



AT 



/x" 



I I 



i 



J 







FIG. 56. AN OPSONIC INDEX CHART. 



foundation. Aside from the 10 per cent, of chances of technical error 

 in making an opsonin measurement, other factors may be present that 

 are entirely beyond control and cannot be measured by the immunisator, 

 and that may seriously affect the value of the opsonic index. 



3. As a diagnostic procedure, Wright has shown that the opsonins 

 possess a certain specificity, and that in a given infection a low index 



