HAEMOLYSIS AND PHAGOCYTOSIS OF RED BLOOD CORPUSCLES 1 9 



In each case equal parts of the serum, of a 5 % suspension of the 

 washed corpuscles of a rabbit and of washed human leucocytes, were 

 employed. 



In the case of the unheated sera the number of leucocytes in 100 con- 

 taining blood shadows was taken as a criterion, and in the case of the 

 heated serum the number of leucocytes containing red blood cells, since, 

 in the latter, no shadows appear. 



The numbers so found for the heated and unheated sera of the 

 immune animal were divided by the number found for the control, and 

 thus figures were obtained representing the opsonic index. Thus, if in 

 the case of the unheated control serum 50 % ^^ the leucocytes contained 

 blood shadows or red blood cells, while with the immune serum in the 

 unheated condition 80 "/^, and in the heated condition 60 % ^f the 

 leucocytes showed erythrocytes or shadows or both in their interiors, 

 then the opsonic index, in the case of the heated serum, was i*2, and in 

 that of the unheated i'6. 



Testing in this way, a curve (Fig. i) was obtained from which one 

 deduces that the more highly immune the serum became the less 

 was the apparent destruction of the opsonin by heat. 



This experiment was only a trial one, but the principle involved 

 seems to be worthy of further exploitation. 



I have to express my warmest thanks to Dr. William Bulloch of the 

 London Hospital for very much kind advice and assistance throughout 

 my work on this subject. 



(319) 



