OPSONINS IN IMMUNITY. 53 



In the previous chapter the accuracy of the method for the 

 determination of the opsonic index has been criticised. It is 

 certain that the method is complicated, requires a considerable 

 amount of experience, and with all the modifications and improve- 

 ments in the technique is still subject to such great error that 

 even in experienced hands the determinations of the opsonic 

 index must be regarded as of doubtful value. 



CHANGES IN THE OPSONIC INDEX IN NATURAL 

 RECOVERY FROM AN INFECTION. 



Wright, at various times, has reported observations on 

 the phagocytic reaction and opsonjc index in infections running 

 favorable and unfavorable courses. He has found that recovery 

 and increased opsonic index accompany each other. Hektoen 

 has reported that in pneumonia the opsonic index is at first low 

 and rises as the patient's condition improves so that at the crisis 

 the index is above normal. In patients that have a persistently 

 low opsonic index in this disease death usually follows. Tunni- 

 cliff has found that in scarlet fever the opsonic index for strepto- 

 cocci is below normal early in the disease and, as the acute symp- 

 toms subside, it rises above normal. Later on it again becomes 

 normal. Ruediger has found in erysipelas a sharp rise in the 

 index for streptococci as the temperature begins to fall. Hamilton 

 isolated pseudo-diphtheria bacilli in 75 per cent of cases of acute 

 otitis media and found wide variations in the index for this organ- 

 ism in these cases. Clark has found that the typhoid opsonic 

 index drops before a relapse in typhoid fever. 



The writer in a study on the opsonic index in erysipelas made 

 observations on the changes in the opsonic index in unvaccinated 

 patients to determine the relation between the opsonic index 

 for Streptococcus erysipelatos and recovery from, migration, re- 

 currence and desquamation in erysipelas. The most instructive 

 of these cases are the two which follow: 



Case I. S., a man, aged thirty-eight years, who had a migra- 

 tory, recurrent erysipelas of the face, ears, scalp, and neck, was 

 admitted to the hospital on the fourth day of his disease. When 

 his face was involved, his index was 0.7; when it was desquamat- 

 ing, the index had risen to 1.3; when his face was again involved 



