AXIS-CYLINDERS 149 



the amount of their breadth, darker spots or points, which 

 give the impression of faint node-like swellings. 



Closer observation, particularly of such preparations as 

 were coloured subsequently in the usual manner with gold 

 chloride, shows in the plainest manner that the fibrillse do 

 not by any means run side by side in complete isolation 

 from one another, but that they are connected by numerous 

 pale threads crossing from one to another. These threads 

 always arise from the nodal points of the fibrillae already 

 mentioned. The structure of the axis-cylinder is proved, 

 therefore, in the clearest manner to be a reticulate mesh work, 

 with somewhat elongate meshes arranged with tolerable 

 regularity in a consecutive series, following the longitudinal 

 direction of the nerve fibre (Plate VIII. Fig. 1, a, &). 



Since it has occasionally been asserted that the fibrillar 

 nature is limited to the external surface alone of the axis- 

 cylinder, I must particularly lay stress on the fact that the 

 same image can be observed both with a surface focus and 

 in an accurate optical section of the axis-cylinder. There 

 can, therefore, be no doubt of the fact, that the axis-cylinder 

 possesses the structure mentioned throughout its entire mass. 

 In connection with this, there is the transverse section to 

 be considered, which we shall shortly describe, and which 

 completely confirms the same fact. 1 



1 I take this opportunity of being permitted to say a few words upon 

 Apathy's remarks (1891) with regard to my preliminary communication upon 

 the foam-like structure of protoplasm, and the corresponding structures of 

 nerve and muscle fibres. I forego examining more closely here Apathy's view 

 as to the structure of the axis-cylinder, since a complete solution of the 

 question will not be possible until Apathy's full work is to hand, with its 

 illustrations. On the other hand, I cannot but state that his objections have 

 not shaken in the least my conviction as to the correctness of my statements. 

 Apathy is willing to allow, on the one side, that foam -like structures are 

 widely distributed in protoplasm, and has, in fact, often convinced himself 

 of the fact. This, he says, is, moreover, nothing new, but was discovered 

 by numerous investigators before me. In consequence, it was quite un- 

 necessary that I should spend so much time and trouble in order to make it 

 probable that the reticular structures so often described in protoplasm ought 

 to be interpreted as in reality alveolar or foam-like structures ; although to 

 my knowledge no one has put forward this idea earnestly before me. 



Nevertheless, however, Apathy believes' that the reticular structures 

 described by me, and later by Schewiakoff, in the contractile elements of 



