IMMUNITY IN PNEUMOCOCCAL INFECTIONS n 



old ; in no case were cultures older than forty-eight hours used. The 

 culture medium employed was glycerine-agar. 



Of the twenty-five cases of acute croupous pneumonia, fifteen were 

 examined regularly from day to day throughout the course of the disease, 

 and the opsonic index of the serum determined before, during, and after 

 the crisis. In the other ten cases it was only possible to obtain the serum 

 at less frequent intervals, but the results in those in no case disagreed with 

 the opsonic curve determined for the others. 



It will be convenient to discuss the relation of the opsonic index to : 



(i) The chill period. 



(2) The course of the disease. 



(3) The final result, whether going on to rapid or tardy resolution, to 

 a fatal issue, or to complications. 



(i) At the chill period I have only been able to examine the serum 

 of one patient. This was obtained two hours after the initial rigor, while 

 the patient was feeling very cold and shivery. The opsonic index stood 

 at -65 ; the original index was unknown, but in a healthy girl, such as the 

 patient, was probably near that of a normal person. 



(2) During the evolution of the disease the opsonic index of the 

 disease is considerably below unity, affording indices varying from 0-45 

 to o*8. The lowest index observed was 0*45, in a poor under-nourished 

 woman, who rapidly succumbed. In fact, all the cases in which the 

 opsonic index fell below 0*5 terminated fatally. Considerable daily 

 variations are present in the development of the disease. A progressive 

 fall in the opsonic content of the serum does not seem invariably to 

 indicate a fatal issue, though such a fall was observed in most of the fatal 

 cases (see Chart I.). 



(3) On the incidence of the crisis the greatest changes take place 

 in the opsonic index. For some twelve hours the amount of opsonin 

 in the serum is vastly increased, and with the increase the patient's 

 condition seems to improve very greatly, and the critical phenomena 

 occur. The amount of opsonin began to increase before any fall 

 in the temperature was noticeable in many cases in which, with a 

 high temperature in the morning, but a normal or higher opsonic index, 

 one could almost predict the critical fall to take place during that day. 

 A pseudo-crisis is not associated with increase in the opsonic index. 



(375) 



