1903.] Role of the Blood Fluids in Phagocytosis. 367 



experiments, conducted both with carmine particles and with Indian 

 ink, were inconclusive by reason of the circumstance that we were not 

 able to obtain any satisfactory enumerations. An impression was, 

 however, left on our minds that phagocytosis was in every case more 

 active in unheated than in the heated serum. 



A third method of experimentation was then resorted to. In a first 

 operation we mixed and digested together at blood heat a suspension 

 of staphylococci and unheated serum. After allowing what we sup- 

 posed would be a sufficient interval for the exhaustion of the effect 

 of the serum upon the bacteria, we divided the mixture into two 

 portions. While the first of these portions was mixed with the 

 corpuscles without undergoing any further treatment, the other was 

 heated to 60 C., and cooled before it was so mixed. In each case 

 the phagocytic power exerted was greater in the case where the 

 heating was omitted, and the differences were not less marked where 

 the serum had been digested with the bacteria for 50 minutes and 

 1 hour respectively than in' the case where it had been digested with 

 these only for 15 minutes. 



These results are ambiguous. 



The question as to whether the blood fluids contain, in addition 

 to opsonins, also an element which directly stimulates the phagocytes, 

 remains for the present unsolved. 



The third series of experiments, which has just been adverted to, is 

 subjoined : 



EXPERIMENT 1. 



S. R. D.'s serum, 3 vols. ; digested with staphylococcus suspension, 

 1 vol., for 15 minutes at 37 C. 



A. 4 vols. of the above mixture heated to 60 C. for 15 minutes, 

 then cooled and added to 3 vols. of S. R. D.'s corpuscles. 



Tube 1. Phagocytic power (bacteria in 16 P.W.B.C. 



enumerated and averaged) 2 2 



Tube 2. Phagocytic power (bacteria in 31 P.W.B.C. 



enumerated and averaged) 20*7 



B. 4 vols. of the above mixture added directly to 3 vols. of 

 S. R. D.'s corpuscles. 



Tube 1. Phagocytic power (bacteria in 16 P.W.B.C. 



counted and averaged) 27 



Tube 2. Phagocytic power (bacteria in 28 P.W.B.C. 



counted and averaged) 



EXPERIMENT 2. 



S. R. D.'s unheated serum, 3 vols. ; digested with staphylococcus 

 suspension, 1 vol., for 50 minutes at 37 C. 



