44 



NA TURE 



[Ngv. 8, 1888 



late the spots n and M : if we stimulate n, everything contracts ; 

 if M, the excited half only. 



The preparation which you now see (corresponding to Fig. 2), 

 and which shows the nervation of the very thin muscle with all 

 the nerve-endings stained dark with gold, makes that relation 

 clear, for here again in truth the result of morphological research 

 is in gratifying accordance with results obtained experimentally. 

 The muscle is seen to be for the most part free from nerves ; 

 indeed the entire nervation with all the nerve-endings might be 



said to be formed of one nerve-//«^ only, if we disregard the few 

 digressing fibres, which, again, in part are not motor. 



Under rather higher powers vi^e see the nerve-endings proper 

 (Fig. 8), the distinct demonstration of which by means of the 

 gold method has now been achieved, in much the same way as 

 here, in all the classes of vertebrates with the exception of the 

 osseous fishes. In all cases these decisive preparations have 

 proved that the vastly preponderant number of the muscle- 

 fibres is entirely free of nerves, and that the nerve-endings are 



confined to very small spots which we term fields of innervation. 

 Most muscle-fibres have only one field of innervation, very long 

 ones occasionally several, at the most eight. Thus the assump- 

 tion, opposed to the idea of independent irritability, that muscle- 

 substance is well nigh completely riddled with nerves, is refuted 

 and rejected from the morphological side also. 



From the absence of nerves in long tracts of muscle-fibre we 

 immediately conclude that the latter shares with nerves the 



faculty of independently propagating its own excitation. Thisi| 

 what the beautiful microscopic observations of Sir WilJiar 

 Bowman ^ on insects' muscles long since led us to suspect. A| 

 in the nerve, so in the muscle, conduction takes place in ever_ 

 direction, and as the field of innervation almost without exceptior 

 occupies a median position during a normal contraction, the con-j 

 duction takes place in both directions, towards the tendinou^ 

 ends. By way of distinction the velocity of conduction 

 according to species, temperature, &c., three to ten times les 

 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 independent] 

 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 contractioi 

 is ended must be regarded as independent and acting in respons 

 to its own direct excitation. 



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

 method we have to employ in order to stimulate according t( 

 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,- a point formerly overlooked 

 comes into consideration — namely, the complication 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 ammonia, have thus far remained free from the 

 suspicion of acting electrically. To these a few others of similar 

 action, such as bisulphide of carbon, ^ have been added, and such 

 as are conveyed to the muscle by 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 •* being the first who showed how 

 strongly it stimulates muscles, while killing nerves without ex- 

 citation. 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 likewise 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 immeasur- 

 able 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. 



Nerves end blindly in the muscles ; as a rule they are not 

 even finely pointed, and still less do they spread out dift'usely in 

 such a way as might make the true ending difficult to find. 

 They end quite distinctly. But the ends always lie beneath the 

 sarcolemma, in such a way that no foreign tissue intrudes 

 between them and the muscle, so that what is fluid in the 

 muscle can directly moisten the nerve. The sublemmar nerve 

 is clothed with nothing else than the axilemma. The nerve 

 never penetrates into the depths of the muscle-substance ; on 

 the contrary, it remains confined to the sublemmar surface of the 

 contractile cylinder or prism. Each nerve- end consists of 

 several branches, like antlers, arising by division, which together 



' "On the Minute Structure and Movements of Voluntary Muscle," 

 Phil. Trans., 1840, p. 457: and " Muscle— Muscular Motion," in the 

 " Cyclopaedia of Anatomy and Physiology," edited by B. B. Todd, vol. iii. 

 1847, pp. 506-530. 



-^ '' Ueber direkte Muskelreizung durch den Muskelstrom," Vienna. 

 Sitzber. k. Akad., vol. Ixxix., Abth. 3, 1879. 



3 "Ueber chemische Reizungen ; nach Versuchen von. stud med. C. lani." 

 Uniersuch. aus dcr Physiol. Instit. dcr Univ. Heidelberg, vol. iv. 1882, p. 

 266. 



* "Experimenta quaedam ad Halleri doctrinam de musculorum irritabili- 

 tate probandam instituta," Krmigsberg, 1857 ; and Virchoxv Archiv, vol. 

 xiii. 1858, p. 421. In there papers, with the discovery of the excitation of 

 muscle by distilled water, appears without doubt the first fact which 

 overthrew the old theory of the equal irritability of muscle and nerve. 



