286 The Phagocytic Power of the Blood 



care of the operator should be to avoid giving so large a dose of the 

 vaccine that the negative phase will be so long continued that harm 

 instead of good may be achieved. 



Although Wright is said to cling to the study of the opsonic 

 index as a guide to bacterio-vaccination and the resulting degree 

 of immmiity, the greater number of workers have abandoned it 

 upon grounds which the writer long ago expressed — "that the 

 estimation of the value of bacterio-vaccination by means of the 

 opsonic index was a very complicated way of finding out very Uttle," 



