16 Dr. J. B. Sanderson. The Time-relations of [May 1, 



that, in direct excitation, contraction begins not more than one 

 four-hundredth of a second after an instantaneous stimulus. 



For measurement of the delay in indirect excitation, the gastro- 

 cnemius (with the index) only was used, the exciting electrodes 

 being applied either at 12 or at 37 mm. from the muscle. The results 

 were not so constant. Corrected for loss of time by propagation 

 along the nerve, the intervals between excitation and beginning con- 

 traction varied from 0'0025" to 0'0035". 



In the experiments for determining the time after excitation at 

 which the electrical response begins and culminates, the capillary 

 electrometer was used, as in my experiments on the heart and on the 

 leaf of Dioncea, as a signal, but with much improved apparatus for 

 recording. 



In the gastrocnemius of the frog, the electrical response to an 

 instantaneous stimulus is indicated by a sudden movement of the 

 mercurial column of so short a duration, that to most persons it is 

 invisible. Its photographic expression is that of a spike projecting 

 from the dark border of the part of the plate which is unprotected by 

 the mercurial column. The electrical interpretation of this spike is 

 that between the contacts two electrical changes of opposite sign and 

 not more than one two-hundredth of a second in duration have imme- 

 diately followed each other, or, more explicity, that the spot excited 

 became, for about 0*0005", first negative, then for a similar period 

 positive, to the other contact (see last paragraph). 



Before using the electrometer as a signal it was necessary to ascer- 

 tain that, under the conditions of the experiment, there was no delay 

 in the circuit, either due to sluggishness of the instrument or to any 

 other cause. It was proved photographically that there is no 

 measurable delay. 



In the muscle (the leading off contacts being on the Achilles 

 tendon and muscular surface respectively, and the nerve excited at a 

 distance of 12 mm.) the electrical response begins at 0'004", and 

 culminates at about 0'012" after excitation. Deducting the delay 

 due to transmission along the nerve, we have, as the time between 

 excitation and response, 0'0035''. It is thus seen that the electrical 

 response, instead of preceding the mechanical, is contemporary with 

 it. All those theories therefore of the excitatory process in muscle 

 which rest on the supposed fact that electrical disturbance is a con- 

 comitant of the period of latent stimulation, fall to tho ground. The 

 electrical change may, so far as concerns the time at which it occurs 

 in muscle, be immediately connected with that sudden change of the 

 elastic properties of muscle of which the contraction is the sign. 



The fact that there is a measurable interval of time between exci- 

 tation and electrical response, renders it improbable that Begecsky 

 is right in supposing that the contraction begins at the moment of 





