330 INFECTION AND IMMUNITY. 



R Vmmuni to ^ an an ^ ma ^ * s injected with a proper dose of 

 processes, bacteria or alien red cells, there results as a rule 

 in the first day or so a fall in the opsonic content 

 of the blood along with other antibodies. This 

 period is known as the "negative phase," and is 

 followed by a steady rise which reaches its height 

 from the eighth to the twelfth day and gradually 

 falls to normal. The negative phase as pointed 

 out by Hektoen is specific and it has not been 

 determined whether it is due to a specific absorp- 

 tion or to an effect on the antibody producing 

 cells. 



"In several acute infectious diseases the course 

 of the formation of new opsonin for the infecting 

 agent, in the typical attack, terminating promptly 

 in recovery without complications, shows a marked 

 general resemblance to the opsonin and antibody 

 curve after a single antigen, injection in the 

 normal animal; it also bears definite and constant 

 relations to the clinical phenomena. During the 

 early stages when the symptoms are pronounced 

 there is a negative phase and then as the symptoms 

 begin to subside the opsonin curve rises above 

 normal, reaching the highest point several days 

 after the onset, followed by a gradual subsidence. 

 This is true of the pneumococcus opsonin in pneu- 

 monia, of the opsonin for the diphtheria bacillus 

 in diphtheria, of the streptococcus opsonin in 

 erysipelas, and also of the opsonin for the dip- 

 lococcus of mumps in that disease. The curve is 

 typical also for the streptococcus in scarlet fever, 

 indicating clearly that this organism unquestion- 

 ably plays a definite role in scarlet fever, whatever 

 its actual causative relation to the disease may be. 



