Vov. 8, 1 888' 



NATURE 



45 



'he terminal nerve-branch. Apart from the form of the 

 ^, this short description is exhaustive for many animals, 

 neither in the sublemmar nerve need any special'additional 

 .ires occur, such as nuclei, nor any kind of modification of 

 uiscle-substance in the field of innervation. There is 

 to indicate that the nerve-fibre proper, or axis- cylinder, 

 lot change its constitution in passing through the sarco- 

 1, still it is to be remarked that the twigs of the terminal 

 hes, although as long as they live often apparently longi- 

 illy striated, have not yet, even in the most favourable 

 ngs, been found to present the general fibrillar structure of 



According to these results of morphological research, it 

 appears that contact of the muscle-substance with the non- 

 medullated nerve suffices to allow the transfer of the excitation 

 from the latter to the former. The only strange thing is that in 

 reversed order excitation of the muscle never extends to its own 

 nerve. This is still stranger because, according to Matteucci's 

 well-known discovery, a foreign meduUated nerve simply laid 

 ui>on the muscle is powerfully excited by the contraction — 

 so powerfully that the smallest contracting muscle barely 

 touching it in more than a mere point excites the strongest nerve, 

 while, on the other hand, we never see muscles excited by nerves 

 which are merely pressed against them. 



In the investments, then, of the nerve and the muscle-substance 

 appears to exist one of the elements which admits the neuro- 

 muscular excitation exclusively to the field of innervation, and 

 among those investments it need not be the medullary sheath. 

 The delicate membranes of the sarcolemma and neurilemma suffice, 

 for muscle cannot be excited by superimposed ;/^«-medullated 

 aerves. At any rate, I have tried in vain to excite muscles 

 by the most intimate contact of the fine terminal ramification of 

 the optic nerve in the retina or the ti. olfactoritis from the pike, 

 )r even the delicate nerves of Anodonta, by stimulating these 

 lon-meduUated nerves. 



If we imagine the activity of the nerve to start with a chemical 



)rocess, and that a chemical stimulant, as du Bois-Reymond ^ 



)nce suggested, is, at the same time, secreted in contact with the 



nuscle, we understand very well the necessity of direct contact, 



xnd in this case it would suffice if the sublemmar nerve were to 



'■" in any form for a short distance under the sarcolemma. The 



hing then would mean the enlarging of the contact. But 



-\er rich and intricate the ramifications may be, we can by 



11 means say they display throughout the principle of increase 



>f superficies ; on the contrary, they are often astonishingly poor 



\r\A small. 'As concerns their form, they are not irregular, but so 



" ':i:;;ly uniform that this point deserves particular attention as 



; apparently indispensable for innervation. 



i:i>iead of describing the forms, allow me to show you the 



itself in a selection taken from the most diverse verte- 



First from the Amphibia (Fig. 9) : rod-like branchings 



ng outstretched twigs, a form which crops up again in a 



able way in many birds. The rule here is asymmetry of 



"sions : all the twigs have the form of a bayonet. 



following preparation shows the termination in the dog 



). Here the branches are crooked, and hence quite 



t, so that the points of agreement with the form of the 



ia are at first overlooked. But if we examine the 



you will remark that these are again unsymmetrical and 



branches whose ends lie verj- diversely removed from the 



place of origin. The ends are, as a rule, turned towards 



er, and often so approximated that it is at times troublesome 



the gaps between them, and if they do not lie in the same 



' ey appear to be united into a ring. In other cases one end 



the other, but we then find that all the points of the 



which are turned towards each other lie at unequal 



from the nearest bifurcation. This law holds good in 



housand cases of motor endings thus far observed, and 



strict order in the apparent chaos of these structures. 



t among the organic forms there is scarcely one which 



much in other respects, and often is so inextricably 



ated as this. 



le drawings (Fig. 11, from the muscles of the guinea-pig, and 



-, of the rat) and a preparation from a lizard (Fig. 1 3) may 



IS a voucher for the truth of the above statement. We 



•-•e there everywhere the hooks making their appearance with a 



hort and a long claw, like the swivel we hang our watch on in 



he pocket. 



' " Gasammelte Abhandlungen' zur allgemeinen Muskel iind Nervenphy- 

 alogie," vol. ii., p. 700. 



The voluntary muscles of all vertebrates and of many inver- 

 tebrates consist of fibres, the contents of which are pefectly 

 regularly disposed in layers and transversely striped. For short- 

 ness, this striped mass may be called "rhabdia." This it is 

 which has been universally identified with the contractile sub- 

 stance. But it has been ascertained that in many cases the 

 nerve-ending does not come at all into direct contact with the 

 rhabdia, but with another mass, which is highly nucleated and of 

 pap-like softness. This latter is unstriped, and has all the 

 appearance of protoplasm. It occurs in very varying quantity 

 under the nerve-antler ; in Amphibia, where the sublemmar 

 nerves run out in a long course, it is not apparent as a separate 

 layer, but it occurs more abundantly in the same measure that 

 the branchings retract, and the field of innervation becomes 

 smaller. At first it is found chiefly between the twigs, in the 

 intervals of the branching, and then in the form of a sole, which, 

 among the much-contorted branchings of reptiles and mammals, 



grows thicker, till it sometimes in some nerve-eminences forms 

 quite a thick cushion. Since we have succeeded in making the 

 nerve-endings visible in uninterrupted series of very fine sections 

 of mammalian muscle stained with gold, there can no longer be 

 any doubt that the complete separation of the sublemmar nerves 

 from the rhabdia by measurable layers of sole-protoplasm, 

 though not the rule, is yet by no means rare, and that many 

 muscles possess no other sort of nerve-endings than such as these 

 with apparently indirect contact.^ 



It would be difficult to understand why the innervation should 

 have in some muscles, as in the Amphibia, no intermediate 

 layer, while having in the majority of cases an interrupted 

 layer, and in others a continuous layer of varying thickness to 

 traverse. But when we consider what the substance of the sole 

 is, of what it consists, how it is distributed, and when we know 

 its origin, it appears that it is identical and stands in continuous 

 connection with the long-known second cjnstituent of muscle- 



fibres, of which, as well as of the rhabdia, the fibres are composed. 

 It is that substance, considered by Max Schultze to be the proto- 

 plasmic remnant of the cells composing muscle, which occurs in 

 greatest amount around the nuclei of muscle, and extends in 

 long threads throughout the entire muscle-fibre. So many trans- 

 verse connections occur on the very numerous stronger and finer 

 nucleated threads that the whole mass, called sarcoglia, becomes 

 a trellis-work almost of the same fineness as the better-known 

 transverse striation of the rhabdia, and everywhere surrounds 

 and interpenetrates the latter. This minute internal structure 

 of muscle has only become at all well known since the intro- 

 duction of gold staining, thanks especially to Messrs. Retzius and 

 Rollett.2 Had it been suspected earlier, and had we appre- 



' Kiihne, Verhanilimgen des XaturkUt.-medicinischen Vereins zrt 

 Heidelberg, Neue Folge, vol. iv. pp. 4, 5. 



'' G. Retzius, " Btologische Untersuchungen," i88i. A. Rollett, "Unter 

 suchungen uber das Bau der quergestreiften Muskelfaser," Witn. Akad. 

 Denkichr.,so\. ytX\%., \%%i. 



