12 QUATERCENTENARY STUDIES IN PATHOLOGY 



In such tests it is a matter of some difficulty to compare heated and 

 unheated sera when undiluted, since the haemolysis produced by the 

 latter is apt to obscure the phagocytosis, but by means of a method of 

 dilution which was adopted, it was found possible to abolish the action 

 of the complement, and thus suppress haemolysis, while phagocytosis 

 could still be observed. By the employment of such a method of 

 procedure it was possible to demonstrate that in corresponding dilutions 

 unheated serum gave a higher phagocytic count than did heated. 



The following experiment illustrates this : — The unheated immune 

 rabbit's serum was diluted so as to give proportions of i in 15, i in 20, 

 I in 30 and i in 60, and of each of these dilutions, one part was mixed 

 in a capillary pipette with one part of a 5 % suspension of the washed 

 corpuscles of an ox and the part of washed human leucocytes, 

 the final dilutions thus resulting being i in 45, i in 60, i in 90 

 and I in 180 approximately. At the same time a similar series 

 was made with serum which had been heated at 55° C. for 15 minutes. 

 A control was made, consisting of i part of "85 % saline solution, one 

 part of the suspension of red cells and one part of washed human 

 leucocytes. Each mixture, as soon as it was made, was placed for 15 

 minutes at 37° C, films being then made, and stained in the usual 

 manner. In each case, 100 polymorphonuclear leucocytes were counted, 

 and the degree of phagocytosis estimated from the percentage of the 

 leucocytes containing red blood cells. This method was found to be 

 more accurate in the case of red blood cells than that of estimating 

 the average number of the red corpuscles taken up per leucocyte, as it 

 was in many instances difficult to distinguish the individual erythrocytes. 



In this particular experiment, the results were as follows (the 

 percentages refer to the leucocytes containing red blood cells) : — 



Dilution. Unheated serum. Heated serum. 



I in 45 65 per cent. 20 per cent. 



I in 60 60 II 6 II 



I in 90 21 I) 4 " 



I in 180 8 II — 

 Saline control, 5 per cent. 



From these and similar results, it is to be assumed that the substance 

 inducing the phagocytosis of red blood cells is partially destroyed by 

 heat, and that, therefore, it cannot be identical with the haemolytic 

 amboceptor or fixateur. 



(312) 



