— 95 — 
appeared as dark points; in longitudinal srctions as dark lines, 
and in oblique sections I could see them as short semi-erect rods. 
There could be no doubt that real fibrillæ of some kind were pre- 
sent, and I was almost disposed to consider Hallers description 
of the nerves, as consisting of bundles of »Primitivfibrillen«, to be 
right. Besides these fibrillæ I could, however, in transverse sections 
see a reticulation, as if produced by transsected tubes; in this re- 
ticulation the transsected fibrillæ were always situated in the walls 
of the meshes, and especially in the junctions of the walls of several 
meshes (i. e. nerve-tubes) the whole had, consequently, somewhat 
of a resemblance to transverse sections of nerves of Annelids and 
Crustaceans. I could, however, in preparations obtained in my usual 
ways come to no certain results. There was, besides, also another 
circumstance which made me certain that those fibrillæ could not 
be real nervous fibrillæ as Haller and Rawitz suppose, this was 
their staining, which was quite that specially pertaining to neuroglia. 
Finally, I succeeded in finding a method of preparing the nerves 
which gave a quite clear idea of their structure. This method con- 
sists in treating pieces of Patella (the pedal muscular disc in which the 
pedal nervercords are imbedded) for about 48 hours in osmic acid 
(i %) then washing them, afterwards cutting them and staining the 
sections as described above (p. 77). 
Examination of sections obtained in this way left no doubt as 
to the structure of the nerves; they contain nerve-tubes having di- 
stinct neuroglia-sheaths, in which thicker longitudinally running fibres 
are situated (cmfr. fig. 19).^) These neuroglia-fibres are the »Primitiv- 
fibrillen« of HALLER and Rawitz. Besides this, there occur stouter 
neuroglia septa orriginating in the outer neurilem-sheath. They 
ramify and divide the nerve-tubes into larger or smaller bundles 
(fig. 19, s, s'). Fig. 19, Jc, h are nuclei occurring in these neu- 
roglia-septa. 
The nerve-tubes are of somewhat varying size, and are usually 
slender and seem to contain but few primitive tubes. I measured 
nerve-tubes having a diameter of .002 — .006 Mm. In some nerves 
the nerve-tubes are, however, much smaller. Fig. 20 is, for instance. 
^) A glance at the origin of the small lateral nerves a' and b' (fig. 19) gives 
a very clear idea of the structure of the nerve-tubes. s\ s' are the neuroglia-septa 
which separate the bundles of nerve-tubes, forming these small nerves, from the rest 
of the great nerve. In a and b some of these nerve-tubes are transversally trans- 
sected in a' and b' they are longitudinally transsected. It is very distinctly see 
that the «fibrillæ» in fact belong to the tube-sheaths. 
