DISTRIBUTION OP NERVES TO STRIPED MUSCLE. 239 



vation in the thinnest part of the membrane, would 

 have afforded far better objects for study ; but from 

 his drawings it is doubtful if he has seen these. The 

 fibre- cells in question would probably not be recog- 

 nisable in his specimens. Had he seen them, he 

 must have noticed the outlines of each individual 

 muscular fibre- cell, and would have observed the 

 nerve-fibres crossing and recrossing them at inter- 

 vals ; and I think he would have been convinced that 

 the nerves passed over, under, and parallel with the 

 muscular tissue, but did not penetrate into the con- 

 tractile tissue or reach its nucleus'. 



These nerve-fibres are extremely fine, and require 

 very high powers for their demonstration. They are 

 certainly not connected in any way either with the 

 nucleus or with the contractile tissue of the muscular 

 fibre. They cross the fibre either obliquely or at 

 right angles ; and oftentimes a nerve-fibre runs for 

 some distance parallel with the muscular fibre. The 

 influence, therefore, exerted by the nerve-fibre cannot 

 depend upon any continuity of texture between it 

 and the contractile tissue, but is doubtless due to the 

 passage of a current through the nerve, which deter- 

 mines a temporary alteration in the relations to one 

 another of the particles of which the contractile 

 tissue consists. 



Upon the external surface of the lung of the frog 

 muscular fibre-cells exist in small number, and to 

 these a network of delicate nerve-fibres is distributed. 

 These muscular and nerve fibres are, however, much 

 more highly developed upon the newt's lung than 

 upon that of the frog. The distribution of nerves to 

 the muscular fibre cells of the arteries is described 

 in Lecture XII, p. 296. 



Distribution of Nerves to Striped Muscle. 

 273. Of the dark-bordered fibres distributed to 

 voluntary muscle. The plexiform arrangement of 



