176 Messrs. 8. G. Shattock and L. 8. Dudgeon. [Dec. 21, 
The action of the patient’s cells would thus appear to be a factor which 
requires consideration if a full estimate of the patient’s hamophagocytic 
resistance is to be arrived at. 
Were the patient’s cells indifferent, normal cells would ingest to the same 
extent as the patient’s cells, in the patient’s serum. This is not the case. 
The patient’s cells may be less active, or they may be more active than the 
normal. 
The conclusion to which the observations lead is that the calculation of 
the opsonic value of the patient’s serum alone does not give a full estimate 
of the patient’s hemophagocytic resistance. It may be too high or too low, 
or, aS a coincidence, it may exactly represent it. 
In what may this greater activity of the patient’s cells consist? The 
greater activity might be ascribed to an elaboration and excretion of opsonin 
by the patient’s leucocytes in the patient’s serum, which brings about a still 
further increased preparation of melanin in the already opsonised serum. 
This would mean that the patient’s leucocytes, instead of playing only the 
secondary part of ingesting prepared bacteria, both prepare and then ingest. 
them. 
To gauge the curative capacity of the patient’s serum only, the method in 
commoner use is doubtless the correct one, for normal cells are used in the 
patient’s serum against normal cells in normal serum. But the question may 
be raised whether the action of the patient’s cells should be considered. For if 
their greater activity is due only to a further secretion of opsonin, in observa-- 
tions carried out in vitro, it may be urged that this exalted phagocytic index 
does not represent that of the circulating blood, but is too high. The patient's, 
cells are transferred to the patient’s serum in relatively abnormal numbers, 
and, during the 20 minutes’ incubation, they may be elaborating from the 
patient’s serum a further amount of opsonin which overcharges the serum. 
in the capillary tube and brings about a fictitious degree of phagocytosis. 
If any substance continues to be produced in the serum, 7 vitro, it must: 
be an opsonin. It cannot be a substance that would stimulate the cells to 
ereater activity: we cannot suppose that the cells produce and shed into. 
the serum a “stimulin” in order to stimulate themselves! The patient’s 
cells produce a further amount of opsonin, or they are simply “ more active” 
than are normal cells. 
One must remember that the process of thrice washing the cells in salt. 
solution does not wash out the leucocyte, it only washes the surface of it. 
One difficulty that arises in testing the alternatives just stated will be 
obvious :—During the process of incubation, in vitro, two phenomena may 
be proceeding simultaneously: the cells may be simply ingesting, or they 
