Dr. J. O. W. Barratt. [Aug. 11, 



the occurrence of spontaneous phagocytosis. When the red blood-cells of the 

 rabbit, for example, are injected into the guinea-pig, opsonin for such red 

 blood-cells develops in the latter's serum, which (after destruction of comple- 

 ment (alexin) by heating for 20 to 30 minutes at 58° C.*) may now be used 

 to sensibilise the red blood-cells of the rabbit. If the sensibilised red blood- 

 cells are added to the leucocytes of the guninea-pig, contained in the (heated) 

 normal serum of the guinea-pig, extremely active phagocytosis of the red 

 blood-cells at once takes place. If, however, sensibilisation is omitted, 

 phagocytosis is still observed, though in considerably diminished degree. 

 Attempts to overcome the disturbing effect of this residual or " spontaneous " 

 phagocytosis have not as yet met with a sufficient degree of success to enable 

 estimations of opsonin to be carried out in such cases. 



There is, however, another class of cases in which spontaneous phagocytosis 

 does not occur. Leucocytes contained in the serum natural to them do not 

 ingest the red blood-cells with which they are normally associated.f If, for 

 instance, the red blood-cells of the guinea-pig are injected into the abdominal 

 cavity of the rabbit and the serum of the latter is employed for sensibilisa- 

 tion, the leucocytes of the guinea-pig, contained in (inactivated) guinea-pig 

 serum are now seen to ingest such sensibilised red cells, though if sensibilisa- 

 tion is omitted no phagocytosis whatever occurs. 



A serum of this kind was prepared from a rabbit, which will henceforth 

 be referred to as Eabbit A. The serum was used for the series of experiments 

 recorded in the tables. 



Rabbit A. — Weight, 2300 grammes. Intraperitoneal injections were made 

 as follows : — 



On the 1st day the red blood-cells of 7*5 c.c. of guinea-pig's blood. 



On the 11th day the red blood-cells of 4*5 c.c. of guinea-pig's blood. 



On the 21st day the red blood-cells of 4'5 c.c. of guinea-pig's blood. 



On the 118th day the rabbit was bled to death. The serum obtained was 

 inactivated by heating to 58° C. for 30 minutes. 



An attempt was first made to ascertain if opsonin could be removed from 

 the serum of Eabbit A by the washed red blood-cells of the guinea-pig, 

 added in varying amounts and acting upon the serum (diluted and undiluted) 

 for periods of time ranging from five minutes to five hours (Table I). During 

 this time the mixture of serum and red cells was continually shaken, either 



* Otherwise haemolysis of the red blood-cells occurs. 



t All the experiments with sensibilised red blood-cells, given in the tables, were 

 accompanied with control experiments on normal red cells. In these, as in numerous 

 other control experiments not referred to here, the results as regards phagocytosis were 

 invariably negative. 



