— 142 — 
a longitudinal course; it is especially prominent near the anterior 
and posterior extremities of the brain where the large anterior and 
posterior nerves issue, and where, consequently, a great many nerve- 
tubes converge towards their roots, causing longitudinal sections to have 
a longitudinal striation (fig. 88), whilst transverse sections of the same 
parts exhibit a distinct reticulation with meshes of about the same 
diameter as the intervals between the longitudinal lines of the longi- 
tudinal sections. In the mesial parts of the brain, the nerve-tubes 
run in more diversified directions, and thus longitudinal as well as 
transverse sections exhibit a reticulation, as tubes are transversally 
transsected in both; some tubes are, however, obliquely, or partly 
longitudinally transsected and appear then, in the sections, as oblong 
or elongated meshes. As the nerve-tubes forming the dotted sub- 
stance vary in diameter, the meshes are consequently also of 
various sizes. 
In the walls between the meshes, slender fibrillæ are seen to 
run in all directions, forming an intricate web or plaiting between 
the tubes, but neither these fibrillæ nor the larger nerve-tubes can 
be seen to anastomose with each other, and thus no real reticulation 
is formed by either of them; the dotted substance consists of a web 
or plaiting of nerve-tubes and fibrillæ^), and it is only the transsection 
of the tubes which, in section, gives the substance the appearance of 
containing a reticulation. 
In macerated preparations of the dotted substance, a great many 
tubes and fibrillæ are easily isolated. Fig. 89 represents such a 
preparation. It is here distinctly seen that, no reticulation and no 
anastomoses are present. From some tubes side-branches are 
given off. 
On examination of the origin of these nerve-tubes and fibrillæ 
it will be seen that they have the very same origin as they have in 
the animals previously examined. A great many come from ganglion 
cells, and a great many pass on to constitute the peripheral nerves, 
and from both fibrillæ and side-branches are given off. 
The nervous processes issuing from the ganglion cells are of 
^) These fibrillæ are partly nerve-fibrillæ, partly neuroglia-fibrillæ. The nerve- 
fibrillæ have, probably all of them, a tube-structure like the larger nerve-tubes; 
i. e. an external sheath enclosing a semi-fluid hyaline contents, hyaloplasm. In 
nerve-fibrillæ which are not too slender, this tube-structure may be seen on close 
examination. The neuroglia-fibrillæ are often seen issuing from neuroglia-cells 
which frequently occur in the dotted substance. I am not in a position to say 
anything with certainty about their structure at present. 
