Huber-DeWitt, Nerve-Endings in Muscles. 175 



of the cross sections of the motor endings (Fig. 30 to 40, 

 plate B). 



The structure of the end-branches of the axis cylinder in 

 motor endings has further been discussed by Feist, Cuccati 

 and Retzius, based on observations made with methylene blue, 

 and while they consider more particularly the motor endings in 

 amphibian muscle, their results may here be presented. Feist 

 is entirely in accord with Kiihne's views. He states that, in 

 methylene blue preparations of frog's muscle, further stained in 

 picro-carmine, the axial thread retains the blue color while, in 

 the stroma, the blue is either entirely displaced by the picro- 

 carmine or it collects in irregular granules. Cuccati describes 

 blue granules in the peripheral part of the branches of the axis 

 cylinders ending in the striped muscle of frog and triton, when 

 stained in methylene blue and fixed in ammonium picrate, and 

 Retzius finds both axial threads as described by Kiihne and 

 Feist and the peripheral granules [Randkomer) described by 

 Cuccati in frog's muscle similarly treated. 



Retzius states however — a point which we will emphasize 

 — in discussing the nerve ending in frog's muscle, that even 

 with very high magnification (Winkel's Imm. Obj. 1-24 and 

 Ocul. 3) "konnte ich keine Structur in den durch Methylenblau 

 gefarbten Endscheiben wahrnehmen. Erst nach dem Zusatz von 

 pikrinsauren Ammoniak trat die iiblich 'Differenzierung' hervor." 

 We may finally add the following comment made by Schafer 

 on Kiihne's observations as above given: "Kiihne regards the 

 axial part as representing the fibrils of the axis cylinder, but it 

 may be doubted whether the differentiation into axial part and 

 stroma is not due to the shrinking of the axis cylinder under 

 the influence of the reagent." 



Our own observations on this point are as follows : In 

 striped muscle tissue from the rabbit, stained vttra vitam in 

 methylene blue, removed to a slide and examined at once, 

 (1-12 oil imm. and No. 3 ocul. Leitz), no structure whatever 

 can be made out in the arborescent nerve ending. All the 

 branches of the axis cylinder have a homogeneous blue color, 

 and while they often show slight thickenings and here and there 



