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For preparative ultracentrifugation, fractions from the column were concentrated by negative pressure dialysis to volumes of 1 ml or less, transferred to cellulose tubes and diluted to 12 ml with isotonic saline.

Ultracentrifugation was then carried out in a Spinco model L ultracentrifuge at 40,000 rpm for 125 to 150 min, refrigeration being used throughout the run.

Successive 1-ml fractions were then drawn off with a hypodermic syringe, starting at the top of the tube, and tested for agglutinin activity.