Abstract
From a study of the effect of irradiation of aqueous suspensions of Escherichia coli with the rays from a B carbon arc, the following conclusions, which harmonize with our hypothesis concerning electrokinetic potential as a measure of activity, stimulation, injury, recovery and death 1 have been drawn:
1. Storage and exposure to atmosphere of room in which the irradiation was carried out were not the cause of the change in electrophoretic velocity noted after irradiation, nor did they change the ability to be agglutinated.
2. Insertion of Corex A glass filter lessened the action of the ultraviolet radiation considerably. This suggests that the shorter wave lengths are more bactericidal and charge-reducing.
3. It has been shown [using both Northrop-Kunitz (maximum and actual values) and Falk capillary cells] that irradiation, if of sufficient duration, produces a decrease in negative charge which accompanies death.
4. Data obtained with the Northrop-Kunitz cell (both maximum and actual velocity) indicate an initial stimulative action of the ultraviolet radiation, which makes itself felt in an increase of negative charge. This increase of charge was not often observed with the Falk capillary cell.
5. Short time irradiation, which merely stimulates or injures, permits of a return toward normal of electrokinetic velocities. Long time irradiation, which kills, produces a lasting effect. 2
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