692 OPSONISATION FROM A BACTERIAL POINT OF VIEW, ETC., 



temperatures This is of considerable importance in the technique 

 of opsonic work, for it is evident that, with a room-temperature 

 of over 12°, the work must be done as expeditiously as possible. 

 It is a mistake to permit the mixture of serum, corpuscles and 

 bacteria in the capillary tubes to remain upon the bench either 

 before or after incubation. After mixture, the test should be 

 incubated and smears made immediately the incubation is 

 finished. 



The experiments show that the optimum temperature is 41 °C. 

 With regard to the regularity of ingestion, although in the 

 majority of cases the 50 count would approximate to half the 

 value of the 100 count, in the minority of cases the differences 

 were sufficiently high to show that 100 leucocytes are the least that 

 should be enumerated. In one case, that of Expt.c. at 41°, two 

 100 counts totalled 647 and 632, while the next count in each 

 case brought the totals for 101 leucocytes to 653 and 652; these 

 were counted along one margin of the far side and the margin of 

 the near side, while across the tip of the same smear 100 cells 

 totalled 650. Although the optimum temperature is 41°, the 

 analysis of the individual counts showed that 37°, 38° and 39° 

 gave the most regular phagocytosis. 



The scrutiny of the counts obtained in the experiments with 

 different fluids, with varying temperatures and times of phago- 

 cytosis, showed that nothing was gained by deviating from the 

 customary method. Some experiments raised the hope that 

 citrate-saline would be better than normal saline for the suspen- 

 sions, but further work showed that no advantage accrued from 

 its use. 



The capillary pipette. — The capillary tubes that are made for 

 holding the tests during incubation are generally very uniform, 

 and for good work it is essential that they should be so. In a 

 wide capillary the phagocytes will settle upon the wall of the 

 tube in a thicker layer than in a narrow one and will not have 

 the chances of meeting so many bacteria. This was shown in the 

 following, in which similar volumes of mixed suspensions and 



