The dynamics of a model of cell division

Abstract

A low beaker is half filled with distilled water and a funnel inserted so that the stem extends to the bottom. A saturated solution of NaCl is slowly poured into the funnel and forms a layer beneath the pure water. About 1 c.c. of a mixture of 2 parts chloroform and 3 parts rancid olive oil is sucked up into a pipette and injected into the beaker so that it forms a drop suspended between the NaCl solution and the pure water. Two pipettes with capillary openings are filled with 1/10 normal NaOH solution and inserted into the beaker. The NaOH solution is allowed to flow onto opposite poles of the drop at the same time and rate. The drop quickly elongates toward the pipettes, i. e., toward the poles, and constricts along the equator, and sometimes divides into two. The smaller the drop, the more certain the division, provided the operator has sufficient skill.

The alkali forms soap which reduces the surface tension on the polar areas, and the hydrostatic pressure within the drop causes these areas to bulge, whereas the relatively higher surface tension of the equatorial region causes it to constrict until a barrel-shaped figure is formed, which rapidly becomes hour-glass shaped. The equatorial surface film contracts and the polar surface film spreads, causing vortex movements. The enlargement of the polar fields spreads the soap over larger areas, and the area of unaltered surface tension is reduced to a narrow equatorial band. This band, being partially released by reduction of tension at its edges, acts as a sphincter and constricts until it cuts the oil drop into two. This constriction of the oil drop may be considered as a rough model of cell division.