1907. | Observations upon Phagocytosis. 181 
tion of the serum, but to the increased time allowed for the cells in which to 
ingest. The practical conclusion we draw is, that in order to estimate the full 
phagocytic resistance of the patient’s blood, the cells should be taken into 
account as well as the serum. 
The method of making such an estimate is considerably simpler and much 
more rapid than the estimation of the opsonic value of the serum only, 
which entails washing normal cells and collecting blood in order to obtain 
both normal serum and the serum of: the patient. 
It is merely necessary to draw up 1 volume of the patient’s blood and 
1 volume of citrated salt suspension of the micro-organism to be used, 
into the capillary tube, to mix, incubate for 20 minutes, spread the film, and 
compare the phagocytosis with that of a volume of normal blood similarly 
treated,—a slight modification of the technique practised by Leishman. 
The washed corpuscles, moreover, sometimes tend to cohere in clumps. 
The central cells of such clusters would fail to reach bacilli presented in the 
fluid. This is probably one explanation of the discrepancies obtained in the 
numeration of ingested bacilli, even in neighbouring fields of the same slide. 
It has been pointed out elsewhere in this communication that although the 
action of the immune phagocyte is usually higher than that of the normal 
cell, yet it may be lower, or it may be equal to it. The cells vary in value, 
like the serum, and the only method of arriving at a correct estimate of the 
patient's hemophagocytre resistance is to allow the immune cells to work in the 
ammune serwm. | 
By the method more commonly employed in this country, too low an index 
is obtained if the patient’s cells are acting above the normal level, and too 
high an index if they are acting below it. 
