604 TRANSACTIONS OP SUB-SECTION K. 



subjected to currents of strengths varying from0'3 to 80 microamperes at 40° C. 

 The effect of this treatment on the activity of the bacteria was detected by 

 measuring the change in electrical resistance of the milk culture after a period of 

 some twenty-four hours. In all cases control cultures of sterile milk containing 

 the same number of bacteria were set up under the same conditions of tem- 

 perature, &c, but having no current passed through them. 



The resistance was measured by means of a Kohlrausch apparatus for the 

 determination of the conductivity of liquids. In this method an alternating 

 current traverses the electrolyte, and a telephone is used to detect the point of 

 balance. All measurements were made with the cultures kept at the same tempera- 

 ture in a water bath controlled by a thermostat. The effect on the production of 

 metabolic products as indicated by the change in resistance of the culture treated 

 was considerable, and seems to be directly due to the action of the current on the 

 bacteria. Counts of the bacteria made by the usual methods also indicated more 

 rapid growth in the electrified culture. The maximum effect seems to be pro- 

 duced by a current of about 60 microamperes. Currents of greater strength 

 inhibit the activity of the bacteria as measured by the change in conductivity of 

 the liquid. 



There was no appreciable difference between the effects produced by direct 

 and alternating currents, so that it seems that no detrimental effect has been pro- 

 duced in the former case by the accumulation of the products of electrolysis in 

 the region of one electrode. 



3. Influence of Electricity on the Respiration of Germinating Seeds. 

 By J. H. Priestley and R. C. Knight. 



In many experiments upon the electrification of plants an acceleration in 

 growth has been reported, accompanied with an earlier attainment of maturity 

 and consequent more rapid harvesting of such electrified crops. 



This appears to indicate an acceleration of the normal vital processes of the 

 plant, and it was thought that an increase in the rate of respiration might act as 

 an index to such accelerated vital processes and enable some idea to be obtained 

 as to the electrical condition most favourable to such acceleration. With this in 

 view a long series of experiments have been carried out, the methods and results 

 of which are briefly summarised below. 



Experiments were carried out to determine the relative amounts of respiration 

 going on in germinating seeds under normal conditions and under the influence of 

 electricity. 



The method was to determine the weight of carbon dioxide evolved in the two 

 cases by absorbing it in baryta solution. A slow stream of air rendered free from 

 carbon dioxide was passed over the seeds, which were enclosed in an otherwise 

 airtight tube or bulb, whichever was best fitted to the required experimental con- 

 ditions. The stream was then carried through a standard solution of baryta in 

 a Pettenkofer tube, where the carbon dioxide was precipitated. The change in 

 the strength of this solution was then determined by titration with a standard 

 solution of oxalic acid, using phenol-phthalein as indicator, and thus the weight 

 ol carbon dioxide present was calculated. 



This Pettenkofer tube was replaced hourly by a fresh one, and, as a rule, the 

 seeds, usually peas, were subjected to normal conditions and electrical influence 

 alternately for an hour each, so that the amount of carbon dioxide in the first 

 tube represented the normal respiration, and the amount in the second the 

 respiration resulting from altered conditions. 



The following sets of experiments were carried out : — 



1. Effect of a Direct Current. — Current was supplied from the college mains, 

 the terminals being connected with unpolarisable electrodes penetrating the rubber 

 stoppers of the long respiration tube. Contact was ensured by packing the seeds 

 tightly together. Currents varying from ()"75 to 9-0 milliamperes were employed, 

 and the results showed a considerable decrease in respiration on electrification, 

 the difference amounting to 20 per cent, or 30 per cent. The higher currents 

 produced a slightly larger decrease. 



2. The same Current Source, direction of the Current rapidly reversed. — 

 A scoliometer was introduced into the circuit in these experiments, and the effect 



