336 Capt. S. R. Douglas. On the Role of the 



opsonic indices to this microbe, however perfect the bacterial emulsion used 

 may be, many of the organisms seen inside the leucocytes are so much 

 digested as to make the counting of the individual cocci, necessary to obtain 

 the average per leucocyte, a more than usually irksome task. 



In view of the fact that there is present in every serum a very marked 

 antidigestive property, namely, the antitryptic power, it would appear 

 almost paradoxical that the serum might play a favourable role in a digestive 

 process, yet on consideration it is quite conceivable that in the case of 

 bacteria or red blood cells the serum might, by some action short of bacterio- 

 lysis or haemolysis, render such bodies more permeable by the digestive fluids, 

 and in this way favour their digestion. 



Eosenow was the first to draw attention to this question, for in working 

 with the pneumococcus he found that the amount of digestion which took 

 place after these organisms had been ingested by the leucocytes varied con- 

 siderably in different bloods, and he came to the conclusion that this 

 variation was due to a property of the serum which acted on the leucocytes — 

 not on the organisms — stimulating them to increased digestive efforts. 



The experiments here detailed have forced upon me the conclusion that 

 there is a property of the blood fluids independent of the opsonic power, 

 which acts directly on the micro-organisms, or, as the case may be, on the 

 red blood cells, rendering them more easily digested by the leucocytic 

 ferments. 



Experiments Made to Ascertain whether Red-Blood Cells or Bacteria which 

 had been Acted on by Serum were capable of being Digested by Solutions of 

 Trypsin or Leucoprotease. 



Preliminary experiments having shown, firstly, that the author's serum 

 had no haemolytic power in regard to washed ox red blood corpuscles ; 

 secondly, that when washed ox red blood corpuscles were mixed either 

 with his defibrinated blood, or with a mixture of his washed corpuscles and 

 serum, large numbers of the ox red blood corpuscles were ingested by the 

 leucocytes, and in them rapidly digested ; thirdly, that even strong trypsin 

 solutions showed no digestive action on washed ox red blood corpuscles, 

 the following experiment was made : — 



After washing ox red blood corpuscles free from all serum by repeated 

 centrifuging with normal saline solution, a 10-per-cent. suspension was made- 

 A series of tubes were now filled in with the following mixtures : — 



Tube I. — One volume of 10-per-cent. suspension of ox red blood corpuscles 

 and 2 volumes of fresh serum (S. E,. D.'s). 



Tube II. — One volume of 10-per-cent. suspension of ox red blood cor- 



