in ELECTRICAL EXCITATION OF MUSCLE 189 



of form in the ring of muscle, which was suitably loaded, 

 could be recorded by the graphic method. On exciting the 

 preparation with the constant current a marked difference 

 appeared, according as the mucosa was present or absent. In 

 the first case contractions occurred plainly both on closing and 

 011 opening the circuit ; but as excitability diminished in pre^ 

 parations that exhibited a certain degree of tonus, the break 

 excitation became more and more prominent its magnitude 

 moreover increasing within a certain range with the duration of 

 closure. After a very long latent period (usually of several 

 seconds) the contraction began so slowly, that the maximum 

 was usually reached after half a minute only. Eelaxation then set 

 in immediately, proceeding as or even more sluggishly. After 

 removing the mucous membrane, Morgen noticed that the closure 

 contraction, as a rule, failed altogether, and only the opening of 

 the circuit was followed by a marked shortening. The same 

 preparation exhibited an analogous reaction when the animal had 

 been poisoned with morphia. It seems highly improbable that 

 the occurrence of the make contraction should in this case be 

 associated with nervous elements (ganglion - cells). It must 

 essentially be an effect of the tonic contraction of the muscular 

 coat, increased by preparation. Bernstein, under whose direction 

 Morgen's investigation was carried out, remarks further that 

 preparations which exhibit frequent and well - marked spon- 

 taneous contractions also give very pronounced contractions 

 at closure, while this is not the case with non-excitable or nar- 

 cotised preparations. 



It has . already been stated that electrical stimuli that are 

 ineffective per se, are, if repeated frequently at a sufficient in- 

 terval, readily summated into an efficient excitation, and 

 Engelmann (I.e. p. 282) established the same fact for closing, as 

 well as for opening stimulation of the rabbit's ureter. The 

 latter also occurs under certain conditions in the smooth muscle 

 of molluscs (Fig. 80). On applying stronger currents, a new 

 and further shortening is seen to occur (especially in preparations 

 not wholly relaxed) after prolonged rhythmical excitation. There 

 can be no doubt that this is an opening contraction, which must 

 be explained by the summation of intrinsically ineffective break 

 stimuli, as already pointed out by Tick in the same connection 

 (4, p. 44 and p. 50). We have no hesitation in recognising in 



