NERVOUS SYSTEM. (Nerve.) 
in the cerebro-spinal system, the grey fibres are 
less numerous, and are seen as grey fasciculi 
lying in the larger mass of white fibres.” 
Neither Retzius nor Muller has given a 
clear description of these organic fibres as seen 
by them. Muller quotes and adopts Remak’s 
account of the microscopic examination of these 
fibres. ‘ They are,” according to the latter 
anatomist, “‘ much more minute than the cere- 
bro-spinal fibres; they are perfectly homo- 
geneous, that is to say, not composed, as far 
__as can be distinguished with the microscope, of 
_ atube and contained portion; and are so pale 
and transparent that in a strong light they are 
not visible; lastly, a completely characteristic 
pearance is produced by the small roundish 
ral bodies Thich here and there beset their 
surface.” They are almost gelatinous in their 
“nature ; they have on their surface the appear- 
ance of fine longitudinal lines, and are easily 
resolved into very fine fibres.* 
Schwann seems to confirm this description, 
and to regard the organic fibre’ as a less per- 
_ fectly developed state of the nerve-tube of the 
-eerebro-spinal system. 
Henle in his description of the grey or soft 
nerves gives the following account of these fibres 
 (fig.334).They are flat fibres,very clear, of homo- 
Fig. 334. 
Gelatinous nervous fibres from a soft nerve in the 
_ Calf ( from Henle. 
_ A, fibre resolving itself into fibrilfa. 
B, A fibre doubled on itself, shewing the flattened 
character. 
C, Two fibres lying in juxtaposition. 
a, a, oa al 
- , c, a nuclear re . 
oe, d, a fibrilla. dnaieaneihte 
_ geneous appearance, in diameter from 0.002 to 
0.003 of a line (g,5th to 44th of an inch), with 
numerous nuclei of cells, round and oval, most 
vA of them laid flat, and arranged at nearly equal 
distances, many presenting regular nucleoli, 
and pointed at their opposite poles. Their 
longest diameter is generally parallel to the 
tudinal axis of the nerve. Sometimes one 
of these fibres resolves itself into more delicate 
fibrille, resembling the primitive fibre of cellu- 
tissue. Acetic acid dissolves them, and 
leaves the nuclei untouched. Henle admits 
that the greyish colour of the nerves depends 
on the quantity of these fibres ; the greater the 
* Miiller’s Physiology, translated by Baly, p. 
‘20, and Remak Obs. anat, et microscop. de sys- 
tem. nervos, structura, 
599 
number of nerve-tubes, the more th bundle 
resembles an ordinary cerebro-spinal nérve. In 
the roots of the sympathetic the number of the 
grey fibres is in large proportion, there being 
four to six of them for one nerve-tube, so 
that each nerve-tube appears surrounded by the 
nucleated fibres.* 
Valentin, who admits the existence of fibres 
of a similar kind to those described by Henle, 
maintains that they are continuations of the 
sheaths of the globules which exist in the gan- 
glia, and which are prolonged from them into 
the nervous trunks, and they serve as an enve- 
lope or protecting sheath to the cerebro-spinal 
nerve-tubes. Henle, who had formerly regarded 
these fibres as nerves distributed to the con- 
tractile cellular tissue and to vessels, (“ the 
slight developement of the nerves of these 
tissues seeming to correspond to the imperfec- 
tion of their contractile power,”) now expresses 
great doubts as to their nature and office, and 
proposes to call them gelatinous nervous fibres ; 
“a name,” he says, “ which has no other end 
but to designate their presence in certain nerves, 
in the same way as we continue to call the 
fibres of cellular tissue, which are met with in 
tendons, tendinous fibres.” 
Miller conjectures that they may serve the 
purpose of establishing a communication be- 
tween the ganglia; in short, that they are so 
many commissures between these centres. 
Purkinje and Rosenthal describe the organic 
nerve-fibre as the same as the central axis of 
the cerebro-spinal nerve-tube deprived of its 
investing membrane, and from comparing the 
sympathetic fibres with the cerebro-spinal fibre 
in the young embryo, they state their opinion 
that the latter, in an early stage of develope- 
ment, is identical with the former, but they do 
not appear to recognise, as Remak did, any 
continuity between these organic fibres and the 
ganglionic globules. 
Volkmann and Bidder have lately put for- 
ward an examination of this question; and 
these observers maintain the existence of a 
series of fibres peculiar to the sympathetic and 
distinct from those of the brain and spinal cord. 
Their work, however, contains many statements 
so much at variance with those of preceding 
writers, and with what I have myself seen, that 
I am led to entertain a strong suspicion that 
there must have been some fallacy affecting 
their observations throughout. 
The sympathetic fibre, according to these 
writers, differs from the cerebro-spinal fibre in 
the following particulars; it exhibits at its mar- 
gin a single contour, instead of the double one 
which is so constant a feature of the cerebro- 
spinal fibre, especially when examined some 
time after death; the distinction between a 
containing tube and the pulpy contents is not 
manifest; the fibre has sometimes a greyish 
aspect, which the authors regard as independent 
of any admixture with material foreign to that 
of the nerve-fibre itself; it is much smaller 
than the cerebro-spinal fibre, nearly one-half; 
in the cerebro-spinal as well as the sympathetic 
* Henle, Algemeine Anat. 
+ Archiv. 1839, p.ccv. 5 
$+ De Formatione granulosa, Vratislav. 1839. 
