104 SOME OBSERVATIONS ON THE STRUCTURE OF NERVE-FIBRES 
I may add that glycerine has proved very useful, not only for permanently 
preserving the preparations in the moist state, but also as an aid to investigation; 
for it renders the sections much more transparent, without making the white 
substance of Schwann invisible, as turpentine does; and hence the course of 
the nerve-fibres through the cord can be traced much more easily, and, at the 
same time, the proportion between the medullary sheath and axial cylinder can 
be readily ascertained. Thus, by examining transverse sections of the cord in 
this way, I find that while KGlliker is quite correct in his statement that the 
fibres of the roots of the nerves diminish in size in passing inwards through 
the columnar regions,’ yet the diminution affects only the white substance, 
the axial cylinder often retaining its full dimensions even in the middle of the 
grey matter, while the medullary sheath is reduced to a very thin crust, so that 
the nerve-fibre assumes a character differing but little from that of an offset 
of a nerve-cell. 
* KOlliker’s Handbuch der Gewebelehre, 3rd ed., p. 285. 
DESCRIPTION OF BEATE AV 
Fig. 1 represents part of a transverse section of the sciatic nerve of a cat hardened by chromic acid, 
and tinted with carmine, the axial cylinder alone having received the colouring matter. The 
specimen was dried and viewed as an opaque object. 
Fig. 2 shows the appearance of thin transverse sections of some nerve-fibres from the same nerve, simply 
hardened in chromic acid, and examined moist by reflected light. The axial cylinder has, under 
this low magnifying power, the aspect of a mere space. 
Fig. 3, similar objects to those of Fig. 2, but seen by transmitted light. 
Fig. 4, a highly magnified transverse section of a nerve-fibre from the same source, prepared like those 
of Figs. 2 and 3, and then tinted with carmine. The carmine colour is seen to affect only the 
axial cylinder and the investing membrane, which, at one part, is torn up from the fibre. This 
sketch also shows the faintly granular structure of the axial cylinder, and the irregularly concentric 
striation of the medullary sheath. 
Fig. 5, a transverse section of a columnar portion of the spinal cord of a cat, also prepared with chromic 
acid and carmine, and examined moist by transmitted light. The fibres vary much in size, but 
all of them resemble those of the sciatic nerve in having the red axial cylinder surrounded by 
a ring of untinted medullary sheath. 
Figs. 6-10 are highly magnified views of some fibres in a section of the cord like that of Fig. 5. They 
present the same characters as the fibres of the sciatic nerve. 
Fig. 11, a fibre from a longitudinal section of a columnar portion of the cord, prepared in the same way 
The axial cylinder alone is carmine coloured, and is, in some parts, stripped of its investing sheath, 
the fibroid arrangement of which is also displayed. 
Fig. 12, a small fibre under similar circumstances. 
Fig. 13, fatty matter in a state of arborescent fibroid aggregation. 
