396 



INFLUBSCE OF THE DILUTION OF SERUM, 



In the ))ext experiment, the action of the light, as compared 

 with the heavy leucocytes, was again tested in 0-8 /o saline; and^ 

 believing that further information might be gained by using con- 

 centrations of serum between the half-dilution and a normal 

 serum, a three-quarter dilution was employed. 



With regard to the leucocytes, these were obtained by washing 

 the total corpuscles in 0*85 ^ saline until they were considered 

 to be free from serum; they were then suspended in a small 

 quantity of saline, transferred to cylindrical tubes, and the 

 volume made up to a depth of 1'75 inches. The tubes were 

 rotated very slowly in the centrifuge for 600 revolutions of the 

 spindle, after which the bottom half-inch of suspension was 

 removed. This contained the heavy phagocytes, the supernatant 

 suspension holding the light leucocytes. This process was 

 repeated several times with the portions until it was considered 

 that the heaviest and the lightest phagocytes had been separated. 

 The suspensions were measured and divided into portions, each 

 of which was washed with the strength of saline desired for the 

 experiment. 



The curves show a marked rise with the three-quarter dilution, 

 which is more than would have been expected from a considera- 

 tion of the curves in its absence. The reversal of the relative 

 heights of the curves at the three-quarter dilution is noteworthy^ 



