The reaction of the protoplasm of the living amoeba to injected salts

Abstract

The salts, NaCl, KCl, CaCl₂, and MgCl₂, in various concentrations both separately and combined, were injected into the living Amœba by means of the micromanipulation apparatus. 1 The bore of the micropipettes averaged between one and two micra in diameter, and the volume of fluid injected could be controlled to amounts varying from about half the volume of the nucleus to that of the entire Amœba. Amœba proteus is ideal for this micro-operative work, not only because of the ease with which it can be injected, but also because of its characteristic reactions to the fluids injected. All the salts introduced produce a momentary dilution, as indicated by a scattering of the cytoplasmic granules in the injected area.

When NaCl or KCl is introduced, the dilution is accompanied by a decided liquefaction of the injected region which becomes quiescent. The surrounding protoplasm then pours into this area where movement ceases. During this quiescent phase the larger and presumably heavier crystalline granules fall to the bottom of this region and there tend to clump against the lower surface of the Amœba. Recovery takes place by a reappearance of currents in and around the quiescent area, and a gradually increasing flow, back and forth, until the Amœba resumes its normal state. The size of the region involved is conditioned by the strength of the salt solution used, and by the amount injected. The Amœba quickly recovers from an injection of a 2M solution of NaCl equal in amount to the volume of its nucleus. If more than this be injected the entire Ameba is converted into a quiescent globule of dead, liquid protoplasm surrounded by a delicate pellicle which readily disrupts when torn with the microneedle.