142 



Mr. C. Russ. An Improved 



[Feb. 21, 



The latter used a mechanism which rotated the pipette on its long axis in 

 a horizontal plane, and their experiments showed no reduction of the errof 

 by its use when tested. 



Only a small benefit is to be expected from such an improvement, but it is 

 probably inappreciable when the entire experimental error may be large, as 

 in the old method. 



Moreover, their method of rotation is not ideal, for though sedimentation 



Fig. 1.— The Opsonic Mill. 



This clockwork-driven instrument standing in the incubator rotates the opsonic mixture 

 and prevents sedimentation of tbe corpuscles. Speed of rotation = 1 min. 45 sees, 

 per revolution. (1) The shortened opsonic pipette. (2) Indiarubber collar. (3) Copper 

 tube lined with fine copper wires. The brake is not illustrated. 



is prevented, there is no active mixing (from end to end of the pipette) 

 induced by such a roller movement. In the device illustrated in fig. 1, not 

 only does no settling occur, but experiments showed that the corpuscles pass 

 up and down in the opsonic fluid during the changing positions of the pipette 

 in the slowly moving wheel. 



After a few trial experiments with the new materials I proceeded to test 

 the opsonic index of the same serum repeatedly, as in the experiments 

 recorded (Table A), to ascertain whether the more even access and mixture 

 of bacteria and leucocytes now improved the experimental error. 



The results are shown in Table B. 



