
1905.| Substance in Serum which influences Phagocytosis. 5138 
microbes for phagocytosis is destroyed by heating for 20 minutes in 60° C., 
only a fractional destruction of the substance occurs. The loss in the case of 
sera, such as normal sera, which contain only a comparatively small quantity 
of the substance, is so great that a method where very small quantities are 
used makes the demonstration and estimation of the substance impossible. 
On the other hand, where a large amount of the substance is present, as in 
certain immune sera, the heating to 60° C. for 20 minutes, or for even much 
longer periods, leaves enough of the substance undegtroyed to give results by 
Wright’s method. Indeed, the counts obtained may be higher than with fresh 
normal serum of the same species. 
One or two experiments may be quoted as examples of a large number done 
which gave consistent results :— 
Experiment.— 
Cocci counted in 
22 leucocytes. 
No. of ingested 
Vol. cocci per leucocyte. 
Fresh normal rabbit’s serum......... 1 
+Suspension of Staphylococcus......... | 9 
+ Leucocytes of horse .................005 1 
Heated normal rabbit’s serum ...... 1 
+Suspension of Staphylococcus ...... 1 0-2 
-+ Leucocytes of horse ..............ceeeeee 1 
Immune rabbit’s serum (heated to 
60° C. for 20 minutes) ............... 1 
+Suspension of Staphylococcus ...... | 20 
+ Leucocytes of horse .................005 1 
The serum of the normal horse, even when heated to 60° C. for 20 minutes, 
gave in certain cases, by Wright’s method, fairly high counts. It contained a 
larger quantity of the substance than heated normal rabbit’s serum. 
Cocci counted in 
22 leucocytes. 
No. of ingested 
Vol. cocci per leucocyte. 
Fresh normal horse serum ............ 1 
+ Suspension of Staphylococcus ...... 1 } 30 
+ Leucocytes of horse ................ee ee 1 
Fresh normal horse serum (heated 
to 60° C. for 20 minutes)............ 1 
+Suspension of Staphylococcus ...... 1 8 
+ Leucocytes of horse ...............0000es 1 
Immune heated serum of horse ...... 1 
+Suspension of Staphylococcus ...... if 60+ 
+ Leucucytes of horse ...............0000 1 
2 ie 
