444 



Dr. W. Kiihne. On the 



identical and stands in continuous connexion with the long-knoAvn 

 second constituent 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 protoplasmic 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 transverse connexions 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 trans- 

 verse striation of the rhabdia, and everywhere surrounds and inter- 

 penetrates the latter. This minute internal structure of muscle has 

 only become at all well known since the introduction of gold staining, 

 thanks especially to Messrs. Retzius and Rollett (21) . Had it been sus- 

 pected earlier, and had we appreciated the volume of the sarcoglia 

 whose existence is thereby shown and which rivals that of the 

 rhabdia, we might have studied this component of muscle in its 

 physiological relations to contractility, as well as in its morphological 

 and genetic relations which are the only ones yet known. 



If now in many cases it appears that the nerve comes in contact 

 only with the surface of a thick layer of sarcoglia, while the rhabdia 

 everywhere is covered by very fine layers of the latter, whose absolute 

 absence in the field of innervation can nowhere be demonstrated, we 

 have to conclude that in general the nerve does not act directly upon 

 the rhabdia, but only on the sarcoglia. This at once gives the latter a 

 physiological interest. We have to ask whether the glia is the 

 medium that conducts the stimulus between nerve and rhabdia, or 

 whether it is itself the contractile element while the rhabdia has a 

 signification other than that formerly attributed to it when we were 

 completely ignorant of the glia. 



All contractile substance requires the co-operation of an elastic 

 element. "Where is this to be found in the muscle-fibre ? The 

 envelope of sarcolemma which is certainly elastic but delicate, and 

 whose mass is almost infinitesimal compared with that of the muscle- 

 fibre, cannot satisfy the requirement ; but more solid structures freely 

 distributed in the paste-like sarcoglia could perhaps do so, and such 

 we find in the rhabdia, in the form of prismatic particles ranged with 

 such constancy and with such regularity longitudinally and trans- 

 versely, that we may hold them to be the elastic element. Then the 

 sarcoglia would become the contractile element, and the nerve would 

 have an easier task. 



I could wish that this view might be accepted as an hypothesis. 

 As far as I can see it does not contradict experience, for it only puts 

 back the muscle nearer to the protoplasm and to all that is con- 

 tractile, and so far coincides with experience that we find muscles in 

 the same measure less elastic and more sluggish in protoplasmic 



