472 



Drs. G. F. Yeo and T. Cash. 



Our method of procedure was to remove the secondary coil of du 

 Bois Raymond's induction apparatus to a considerable distance from 

 the primary and gradually to approximate it, testing both directions of 

 the current in each instance till distinct contraction producing a legible 

 curve was obtained. Electrodes were applied to both nerve and 

 muscle, so that the position of the secondary coil at which direct or 

 indirect stimulation caused contraction might be noted. A much 

 more closely approximated position of the secondary coil to the 

 primary is necessary for direct stimulation to be effective than for 

 indirect. One Daniell was employed in the earlier experiments and in 

 the later two Grove's elements were introduced into the primary 

 circuit. 



A contraction first occurred when the secondary coil (opening 

 shock indirect) stood at 28 centims. No other mode of stimulation 

 was effective till an approximation of 9 centims. was reached, when 

 an indirect closing shock became operative. At 6 centims. direct 

 opening shocks produced contraction, but the most powerful direct 

 closing shocks, of which the apparatus and the single element were 

 capable, were ineffective. 



The contraction here, though maximal for indirect was submaximal 

 for direct stimulation. The shock was at no point exhausting to the 

 muscle for the altitude and length of the contraction, except in the 

 case of the first, which is distinctly submaximal, remain remarkably 

 constant throughout the experiment. The total result of the experi- 

 ment may be expressed in four figures. 



Gastrocnemius. Indirect stimulation : increasing strength. 



1st stimulation : coil at 28 centims Latency=3 T 



10th „ „ 19 , „ 2-95 . 



20th. „ „ 10 „ . . . . „ 2-90 . 



30th „ „ „ . . . . „ 2-85 



or, in other words, the diminution of latency under this increase of 

 stimulation was only '15, or the "OOOS", an effect so slight that it may 

 pass almost without notice in ordinary experiments, but is nevertheless 

 of sufficient value in showing that an increase of intensity of stimula- 

 tion, only carried so far as to produce a continuance of healthy re- 

 action, still modifies the latency to a certain extent. The temperature 

 of the room, 17 0, 5 0. remained constant during this observation. 



In another experiment, two Grove's cells (small) were substituted 

 for the Daniell, and thus a much greater potential was available for 

 stimulating purposes. The muscle was uncurarised and the stimula- 

 tion direct. 



