— se- 
in these filaments we certainly find small dark granules (fig. 6, a) 
which, occur however, only in the point or knots where several 
filaments unite; they never occur in the centres of the meshes. And 
the same reticulation is extended through the whole transvers e sec- 
tion of every nerve-tube, and fills the whole space inside the 
tube-sheat. 
If we, now, compare the impressions which transverse sections of 
the nerve-tubes give, with those obtained by longitudinal sections, there 
can, in my opinion, be no doubt left but, that the „fihriUcB" of most 
writers helong to a suhstance, spongioplasm, forming a bundle af 
slender, cylindrical tubes or channels enclosed in the neurilem-sheath 
of each nerve-tube. These primitive tubes, if we may call them so, 
are filled with the homogeneous, viscous substance, hyaloplasm, ivhich 
we already Tcnow from fresh nerve-tubes.^) The granules in the transverse 
sections show themselves to be transsected thicker longitudinal fibres 
of spongioplasm which, occur especially along the longitudinal edges 
where several tubes, usually three, meet. If we imagine the spongio- 
plasm as forming cylindrical tubes laid or pressed together, it will 
be evident, that the spongioplasmic walls of the different tubes will 
unite and form septa, as the spongioplasm cannot, of course, be 
considered as a quite solid and unadherent substance ; it will also be 
evident that, in the corners where several tubes meet the spongio- 
plasmic walls will be still thicker. 2) 
In this way, I think, we may easily understand why it was so 
extremely difficult to isolate and get a clear idea of SCHULTZEs 
»Primitivfibrillen«. As we have seen, they do not exist in the way 
he has explained ; what he called fibrillæ, are the spongioplasmic walls 
between the real » primitive fibrillæ « or primitive tubes as I have 
called them. 
The above description refers to the structure of nerve tubes, 
which are, I think, in the most primary state. 
There are, however, in the longitudinal commissures, as well as 
also in the peripheral nerves a great many tubes exhibiting a kind of 
concentration towards an axis in their centre. — As described p. 8i, 
a more or less concentrated longitudinal striation was visible in the 
^) The primitive tubes have a diameter of abont .0015 — .0017 Mm.; their 
size vary, however, and is very difficult to measure. 
2) There occur, however, besides these granules larger dark granules, as well 
in transverse sections as in longitudinal ones. They are usually very sparingly spread, 
especially near the centres of the nerve-tubes, as will shortly be mentioned and 
hey are always situated in the spongioplasmic walls of the primitive tubes. 
