PHAGOCYTOSIS 



2 6 5 



majority lie much nearer to i. When the estimations are carefully 

 carried out, very few will be found below 0-95 or above 1-05. We 

 may regard the opsonic index for a given organism as a definite 

 quantity in a healthy person. Some sera are lower or higher than 

 others, but the difference is but slight, and the index of the same 

 person is found to show but slight daily variations as long as he 

 remains in good health. A few observations go to show that the 

 index is slightly lowered in persons who, without being ill, are in a 



Serum 4: 1 



3:2 2:3 



1:4 N.Saline 



FIG. 59. SHOWING EFFECT OF DILUTION OF NORMAL SERUM ON THE 

 NUMBER OF BACTERIA TAKEN UP. (Original.) 



state of lowered vitality, and that the onset of a mild disease, 

 such as a cold, may cause a fall in the index to tubercle or other 

 disease. 



When the patient suffers from a disease due to a given organismi 

 and his index is tested against this organism, the results obtained 

 are of extreme interest. Taking the acute diseases first, we find 

 that as a rule the index is low at the commencement of the illness, 

 and that it rises, either gradually or suddenly, when recovery 

 takes place; and in some cases there is a definite correlation 

 between the course of the index and that of the disease. For 

 example, Macdonald has shown that in an attack of pneumonia 

 the opsonic index of the patient's serum to the pneumococcus 

 remains at a constant low level until the crisis is reached, when it 

 shows a sudden rise, attaining a point above the normal level. It 

 remains elevated for a short time, and then relapses to normal or 

 below normal. It is difficult to believe that the rise in the opsonic 

 index and the consequent increase in phagocytosis which w 



