TERMINATION OF MOTOR NERVES IN VERTEBRATA. 223 



contractile substance, the granular substance of the nerve 

 eminence, the nerve plates, and the sarcolemma, which un- 

 doubtedly lie in that order from within outwards. Moreover, 

 transverse sections of frozen muscles with their nerve eminences 

 afford an insight into the thickness of the nerve plates. They 

 show that this, as a whole, is not inconsiderable; that in the 

 central part it is nearly as large as the short diameter of a 

 nucleus of the basis substance, though at the edges and irregu- 

 lar processes it is far smaller; so that were it not for their 

 transparency the transverse sections of these parts might be 

 mistaken for granules of the basis. 



Preparations made with osmic acid stain the nerves as far as 

 the apex of the nerve eminence of a bluish black colour, whilst 

 the contractile substance, the nerve plate, and the basis sub 

 stance assume a clear yellow tint, and fat molecules in the 

 muscle become brown, reactions which prove that the whole 

 mtra-muscular nerve termination loses the characteristic consti- 

 tuents of the nerve medulla. The terminal nerve plate can be 

 brought into view in an isolated condition, though certainly 

 not situated externally to the muscle, without other addition 

 than clear muscle serum. Isolated muscular fibres from the 

 lizard, fixed under a covering glass, frequently exhibit, when 

 they are in a complete state of rigor mortis, such contractions 

 of the muscle coagulum, that large balls of this material 

 accumulate in swollen portions of the sarcolemma, between 

 other smaller spaces, filled only with muscle serum. If the last- 

 mentioned empty spaces happen to occur at the place of the 

 nerve entrance, the plate hangs free in the lumen of the sarco- 

 lemma, and it is deserving of notice that it even then still 

 adheres to the protoplasmic substance and nuclei which consti- 

 tute the basal substance of the nerve eminence. It appears, 

 therefore, that further investigation is requisite to enable a 

 positive statement to be made in regard to the union that exists 

 between the two constituents of the nerve eminence. 



From what has been now advanced, we may conclude, then, that 

 the appearances presented by the extremities of the motor nerves 

 are so various that scarcely any scheme can at present be con- 

 structed that shall give a representation, the morphological and 

 physiological features of which shall be applicable to all animals. 





