Cataphoretic Velocity of the Typhoid Bacillus as a Function of Culture Age and Type of Medium

Abstract

The recent interest of chemists and physicists in surface phenomena has accompanied an increasing attention to interfacial conditions in biological sciences. The bacteriologist now looks hopefully toward electrical measurement of certain surface characteristics as a key to facts inaccessible to former methods. Measurements of ^-potential by microcataphoresis cells have been placed on a sound theoretical basis by Ellis,1 Smoluchowski2 and others, while notable contributions to technic of such measurements have been made by Northrop and Kunitz3 and Abramson.4 Like many another technic involving electrical determinations, however, microcataphoresis presents numerous possibilities for error to inexperienced, while interpretation of f-potential requires mastery of certain hydrodynamic and electrical theorems not usually included in biologist's training. In surveying growing literature on microcataphoresis as applied to bacteriology and immunology, one is struck by large number of experiments which ambitiously attempt to relate f-potential to such large aspects of bacterial activity as virulence and organ-specificity, while number of attempts to determine simple basic variables seems relatively small. There has arisen in certain quarters a tendency to forget or neglect true significance of f-potential: that of a relation between and suspending fluid in which measurements are made, a meaning inherent in word potential, which implies relativity. Thus one finds f-potential considered by some as an absolute characteristic of a given organism, much like ability to ferment lactose or reaction to Gram stain. It is needless to refer here to large volume of experimental work which has demonstrated f-potential to vary in a generally predictable way with concentration of specific ions in suspending medium, or to point out that to speak of the f-potential of an organism without reference to medium in which it is measured is just as meaningless as to speak of velocity of a man without stating whether he is moving on land, swimming in water or falling freely through space. Even among those who well appreciate relativity of f-potential, however, there prevails feeling that if ionic concentration is carefully controlled and suspending medium kept constant in all other respects, then