Abstract
An instrument is described which rapidly determines both numbers and volume distributions of dielectric particles suspended in a conducting solution. The volume distributions are shown to be independent of the suspending solution conductivity over a large range, and they can be repeated at about 10 sec intervals with sample volumes of 0·05 ml. Data are presented showing the linearity of the system, the effects of counting rate on the volume distributions, and a comparison of the absolute modal volumes of two different mammalian cells grown in tissue culture and two different pollens, as determined by this instrument, with the modal volumes measured by optical methods. It is concluded that the instrument can be used to determine the absolute volumes of tissue culture cells to within 20% and may provide the only way to determine the actual volumes of such irregular objects as pollen.