498 



Prof. J. C. Bose. Influence of Electric 



Length of spine between the electrode and the nerve = 40 mm. ; length 

 of nerve = 90 mm. ; length of muscle = 50 mm. ; length of tendon = 30 mm. 

 Stimulus is applied in all cases on the nerve, midway between the two 

 electrodes, this point being at a minimum distance of 100 mm. from either 

 electrode. The point of stimulation is, therefore, situated at an indifferent 

 region. 



Great precautions have to be taken to guard against the leakage of 

 current. The general arrangement for the experiment on animal nerve is 

 similar to that employed for the corresponding investigations on the plant. 

 The choking coil is used to prevent the stimulating induction current from 

 getting round the polarising circuit. The specimen is held on an ebonite 

 support, and every part of the apparatus insulated with the utmost care. 



2. Variation of Velocity of Transmission. 



In the case of the conducting tissue of the plant a very striking proof 

 of the influence of the direction of current on conductivity was afforded by 

 the induced variation of velocity of transmission. Equally striking is the 

 result which I have obtained with the nerve of the frog. 



Experiment 5. — The experiments described below were carried out during 

 the cold weather. The following records (fig. 7), obtained by means of the 

 pendulum myograph, exhibit the effect of the direction of current on the 



Fig. 7. — Effect of heterodromous and homodromous current in inducing variation in 

 velocity of transmission through nerve. N, normal record ; upper record shows 

 enhancement and lower record retardation of velocity of transmission under 

 heterodromous and homodromous currents respectively. 



period of transmission through a given length of nerve. The latent period 

 of muscle being constant, the variations iu the records exhibit changed rates 

 of conduction. The middle record is the normal, in the absence of any current 



