These memltr anes or sheaths of the ganglion cells have 
the same structure as the sheaths of the nerve-tubes, and are formed 
of the same substance, viz. the netiroglia; nuclei, having the appear- 
ance of common neuroglia-nuclei, occur frequently in them, and are 
generally adherent to their outer side ; I have seldom observed nuclei 
situated on the inner side as described of the nerve-tubes. The 
sheaths, enveloping the cells, very often consist of several layers or 
membranes, similar to what is described of the sheaths of the 
nerve-tubes. 
I can not decide, whether inside these layers of neuroglia-sub- 
stance there also occurs a thin membrane, spongioplasmic membrane 
(different from the neuroglia-sheath), belonging to and arising from 
the protoplasm of the ganglion cells. It would, consequently, be a 
»cell-membrane« as many writers describe it to be, but the existence 
of which other writers deny.^) The importance of such a membrane 
existing, or not existing, is, however, in my opinion," not great as 
may be seen from the subsequent description of the structure of 
the cell-protoplasm. 
When several writers deny the existence of a cell-membrane, 
as well as a membrane of connective substance, I think that must 
arise from their examining macerated preparations, and imperfectly 
stained sections. In macerated preparations, it is often very difficult 
to distinguish the enveloping membrane from the cell-protoplasm, it 
having a concentric striation which is very similar to the outer 
layers of the protoplasm ; neuroglia-nuclei are, however, usually ad- 
herent to its outer side and indicate its real neuroglia nature 
(cmfr. fig. 23, n). 
In successfully stained sections, e. g., sections stained with 
Heidenhains hæmatoxylin-method (vide p. 76), the neuroglia mem- 
branes are, even under the lower powers of the microscope, distinctly 
visible (fig. 24 — 29). ' In such preparations, these membranes also 
appear to be intimately connected with the neuroglia-reticulation 
extending between the ganghon cells (cmfr. fig. 24), and they look as 
if they belonged to that substance, which, in my opinion, is also 
^) If such a special spongioplasmic membrane occurs, which is, in my 
opinion, not improbable, it would, I think, be so intimately connected with the 
surrounding neuroglia-membranes (cmfr. my subsequent description of the cell- 
protoplasm and its reticulation) and have an appearance so perfectly similar to 
them that, I cannot understand how authors, working with macerated preparations, 
can describe special cell-membranes as being different from the surrounding 
»connective-tissue« membranes. 
