440 



Dr. W. Klihne. On the 



conduction is, according to species, temperature, &c, three to ten 

 times less than von Helmholtz fixed it for nerve. As conduction in 

 irritable tissues means nothing else than that one excited spot 

 becomes the stimulus for the adjoining portion at rest, the in- 

 dependent irritability of the muscle-fibre comes into employment 

 in every movement and during the entire duration of life ; from the 

 moment that the field of innervation becomes active all the muscle 

 substance remains left to itself, and until the contraction is ended 

 must be regarded as independent and acting in response to its own 

 direct excitation. 



Once clear on the fundamental question, and sure as to the method 

 we have to employ in order to stimulate according to choice either 

 muscle or nerve- substance alone, or both together, we may seek to 

 determine in what respect the irritability of the two components of 

 the motor machine differs. The differences as regards chemical 

 stimulation appear very great; in respect of electric, thermic, and 

 mechanical, on the other hand, only quantitative. However, under 

 chemical stimulation, according to Hering's classical researches (16), a 

 point formerly overlooked comes into consideration, namely, the com- 

 plication introduced by the electromotive behaviour of the tissue, an 

 automatic electrical stimulation one might say. When stimulation 

 takes place by moistening the transverse section with conducting 

 liquids, it is indeed difficult, if not impossible, to trace the chemical 

 factor in presence of the electrical. Gaseous stimuli alone, like am- 

 monia, have thus far remained free from the suspicion of acting 

 electrically. To these a few others of similar action, such as bisul- 

 phide of carbon (17), have been added, and such as are conveyed to the 

 muscle by the blood-vessels, and bathe the fibres from all sides. With 

 these in particular we may class distilled water, which is excessively 

 destructive to irritable substances, von Wittich (18) being the first who 

 showed how strongly it stimulates muscles, while killing nerves 

 without excitation. But, again, with this kind of stimuli, we cannot 

 at present tell whether they do not set up in the tissues, over narrow 

 but numerous areas, excitatory electric currents, thus working only 

 indirectly by way of auto-electric stimulation. And since, finally, the 

 same might apply to the thermic and mechanical actions which like- 

 wise arouse demarcation currents in the muscle, that is, to all stimuli, 

 we find ourselves in the presence of the possibility of reducing all 

 irritability to a reaction to electrical processes, and of seeing vital 

 electricity elevated into immeasurable importance. 



The means by which muscle may be stimulated interests us, in the 

 first place, on this account — to ascertain, once for all, how it procures 

 its excitation in life, or what may be the action of nerve upon it. Did 

 we know that, we should have grasped at the same time the nature of 

 nervous activity. 



