An Electrometric Study of Mimosa *

The fact that living organisms exhibit certain electrical phenomena has long been known, but understanding of their significance and meaning is limited. The attempt to explain the several aspects of biological activity which can be recorded by electrical devices has, in general, rested on the assumption that the underlying phenomena are chemical and that the electrical records represent by-products of biological activity. It is not surprising, therefore, that many studies have been made of ionic transport, electrolyte balance, and similar chemical processes in the hope that they would yield significant and conclusive evidence not only as to the source of the potential differences but also as to their meaning and significance. The results have not been very satisfactory, for it is not yet clear what chemical entities or processes either give rise to or modify potential differences. It is well known that in all biological systems a multiplicity of phase iboundaries exist. Furthermore, the existence of potential differences at these phase boundaries is generally accepted. It is commonly held also that the membrane potential at a phase boundary is the consequence of a difference in concentrations of electrolytes on opposite sides of the boundary. In the non-living system this potential approaches zero as ionic equilibrium is reached. It has been more or less logically conduded, therefore, that the existence of and variation in potential difference can be explained by the known initial difference in concentrations and by ionic movement across phase boundaries. The living system differs somewhat from the physico-chemical situation in that the potential differences, instead of approaching zero with time, are maintained at an astonishingly stable level. The maintenance of this level of potential difference presupposes constant recruitment and it is natural to assume that this recruitment comes in large measure from chemical activity. But it is not at all impossible that one of the mechanisms regulat-