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Myelinated fibers in gray rami communicantes.

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MYELINATED FIBERS I N GRAY RAM1
COMMUNICANTES
JOSEPH PICK
Department o f Anatomy, N . P. 17.-Bellevue Medical Center,
College of Yedicine, New Pork
TWENTY-TWO FIGURES
INTRODUCTION
Myelinated fibers measuring from about 1.5 p up to 12 p
o r more in diameter, are present in the gray rami communicantes of the cat (Langley, 1892, 1896; Kuntz and
Farnsworth, '31), of the Rhesus monkey (Sheehan and Pick,
'43) and of man (Pick and Sheehan, '46). These fibers have
been variously interpreted. Langley (1892, 1896) considered
the majority of myelinated fibers measuring from 2 p-8 p as
postganglionic with their cells of origin located in the lumbosacral sympathetic trunk. He regarded only a very small
proportion of myelinated fibers of similar or even larger size,
to be afferent with their trophic centers placed in dorsal
root ganglia which are several segments distant from that
at which the myelinated fibers pass through the gray ramus.
This author suggested that some myelinated fibers in gray
rami are somatic, supplying the lumbar muscles or, that
they are afferent of "some special sense," similar to that
of the depressor nerve (De Cyon and Ludwig, 1866). Langley
(1896) also interpreted a few myelinated fibers as preganglionic, which may, occasionally, extend into gray rami, where
they synapse with aberrant sympathetic cells. Dogie1 (1896)
described afferent or commissural fibers arising from the
ganglia of the sympathetic trunk. The existence of such
neurons could subsequently not be confirmed (Langley, '04;
Cajal, '11; Carpenter and Conel, '14 ; Ranson, '18 ; Johnson,
395
TEE ANATOMICAL RECORD, VOL.
DECEMBER, 1956
126, NO. 4
396
JOSEPH PICK
’21, and Nevin, ’30), although an occasional pseudo-unipolar
cell which had gone astray from the dorsal root ganglion can
become incorporated in the sympathetic trunk (Paarmann,
’50).
Muller ( ’09) did not look upon these rami as being “gray”
at all, but regarded them as “white,” because he considered
all myelinated elements contained therein, as preganglionic.
Kuntz and Farnsworth ( ’31) claimed that only comparatively
few myelinated fibers measuring not more than 2 . 5 ~are
postganglionic with their cells of origin in sympathetic ganglia. The considerable number of myelinated fibers of larger
size with “a dark ring and clear center” present in gray rami,
were interpreted by these authors as pain-bearing from the
blood vessels of the extremities.
Recently, Kuntz (’51) once again associated the myelinated
fibers larger than 2 . 5 ~in gray rami of the brachial and
lumbo-sacral plexuses with the conduction of pain from the
blood vessels of the limbs, on the basis of his anatomical and
experimental studies in cats and his observations of the effect
of stimulating the lumbar sympathetic trunk in a patient.
On two diagrams he illustrated specific pain pathways from
the blood vessels of the limbs across the nerve plexuses, their
gray rami communicantes, sympathetic trunk and on into the
spinal cord, by way of dorsal root ganglia placed at different
levels than those at which the alleged pain-conducting fibers
had passed through the gray rami.
I n view of the clinical implications and the wide disagreement that still exists regarding the actual number of such
fibers and as t o which of their functions has the greatest
importance, a re-investigation was made of the source and
distribution of the myelinated component in the gray rami
communicantes of the lumbo-sacral sympathetic in the cat.
For this inquiry, the method of nerve degeneration was chosen,
particularly also, because the results obtained thereby could
then be readily compared with the data reported by other
authors (Langley, 1892, 1896 ; Kuntz and Farnsworth, ’31;
Kuntz, ’51) who worked with the same animal and whose
MYELINATED FIBERS IN GRAY RAM1
397
evidence rested largely upon the effect of severance of the
sympathetic trunk and/or the elimination of the spinal roots
and root ganglia in the lumbo-sacral region.
METHODS AND MATERIALS
For purposes of comparison, all 7 lumbar and three sacral
rami communicantes and all internodal rami of the lumbosacral sympathetic trunk were studied bilaterally in three
normal cats, and in the normal side of 6 cats in which a unilateral operation on the sympathetic had been performed.
Nerve degeneration experiments were carried out unilaterally in 17 cats.
In one series, consisting of 7 cats, the sympathetic trunk
was divided above and below the 6th lumbar sympathetic
ganglion.
I n a second, the division of the sympathetic trunk above and
below the 6th lumbar sympathetic ganglion was followed by
the removal of both spinal roots and dorsal root ganglia of
the 6th and 7th lumbar segments in 4 cats. I n addition, in
one animal of this series, the spinal roots and dorsal root
ganglion of the 5th lumbar segment were also removed, and
those of the 1st sacral in another.
Thirdly, both spinal roots and the dorsal root ganglia of the
4th, 5th and 6th lumbar nerves were removed in 2 cats, and
those of the 6th and 7th lumbar and 1st sacral nerves in one.
Finally, the division of the sympathetic trunk between the
2nd and 3rd (one cat) and between the 3rd and 4th (two
cats) lumbar ganglia was followed by the excision of both
spinal roots and dorsal root ganglia of the 1st lumbar down
to the 2nd sacral segments (one cat), of the 2nd to the 7th
lumbar (one cat) and of the 1st lumbar down to the 2nd
sacral, leaving the 5th spinal roots and dorsal root ganglion
intact (one cat).
The time allowed for degeneration of sympathetic nerves
ranged from 31-98 days, and for that of the spinal nerve roots
from 19-50 days.
398
JOSEPH PICK
The normal cats furnishing the control material as well as
the experimental animals were fixed, under nembutal anesthesia, by intravascular and intraperitoneal injection of a
10% formaline saline solution. I n each instance, all sympathetic rami of the lumbo-sacral region were dissected with
the aid of a magnifying glass and recorded on a diagram
in complete detail. Subsequently, all rami communicantes,
internodal rami of the sympathetic trunk, and in several
instances also the splanchnic nerves were excised and prepared
for histological examination using 1%osmium tetroxide for
staining. Representative sections of these nerves were cut at
4 p in thickness. All myelinated fibers in the gray rami of the
lumbo-sacral region were counted and measured. The counts
of myelinated fibers in white rami communicantes, individual
internodal rami and in the splanchnic nerves of normal cats
was restricted to fibers measuring more than 4.5 p in diameter.
All counts and measurements were made on prints of enlarged
photomicrographs, and checked in every instance by an appeal
to the microscope.
In each, the three lower lumbar and two upper sacral segments of two additional cats, the spinal nerve together with
the rami communicantes, sympathetic ganglion and, in some
instances, the splanchnic nerve were excised en bloc, mounted
on a piece of cardboard and placed in 1%osmium tetroxide
without previous f ormalin fixation. Subsequently, serial sections at 4 p in thickness were taken across the rami communicantes and splanchnic nerves.
I n three cats, the proximal part of the inferior mesenteric
artery together with the adjacent aorta, and the aortic bifurcation were removed under nembutal anesthesia and impregnated with silver, using the method of Nonidez ( '39) in some
instances and the Bodian stain modified by Johnels ( ' 5 5 ) in
others. These preparations were cut at 10 p in thickness.
I n another series of three cats which had been anesthetized
with nembutal, the inferior mesenteric artery was ligated
1em distal to its origin, and additional ligatures were placed
around the aorta above and below this point. Extreme care
MYELINATED FIBERS IN GRAY RAM1
399
was taken to avoid any injury to the adjacent nerves. Simultaneously, the right common carotid artery was exposed and
connected with a mercurial manometer. The vascular cul de
sac was distended by the injection of approximately 0.5 cm3
saline solution and any change resulting therefrom, was read
directly from the manometer. These physiological experiments were carried out together, with my colleague, Dr.
Chester W. Hempel.
I n this study, reference will be made to the results of
lumbar sympathectomies which were performed together with
the late Dr. Hippolyte M. Wertheim, in patients suffering
from “vascular pain. ”
FINDINGS
The normal distribution of myelinated fibers ilz the
lumbo-sacral sympathetic (tables 1,2,3)
Myelinated fibers in these sympathetic rami were classified
in two groups: (a) fibers measuring up to 4.5 p and (b)
fibers larger than 4.5 and measuring up to 12.5 p.
I n the gray rami communicantes (table I), the highest
proportion of fine myelinated fibers measuring up to 4.5 p
was found in the 6th and 7th lumbar segments. Larger
myelinated fibers were either absent or their number was very
low. However, the range of variation occurring in the number
of myelinated fibers of all sizes is rather wide in every one
of the lumbo-sacral gray rami.
The distribution of myelinated fibers over 4 . 5 ~in the
internodal rami (table 2) and in the white rami cornmufiicantes
(table 3) did not indicate that the large fibers in the gray
rami of the lumbo-sacral plexus ascend in the sympathetic
trunk and white rami of the upper lumbar region. As will be
seen in tables 1 , 2 and 3, and, particularly on figure 1illustrating a specific case, the sum of myelinated fibers larger than
4 . 5 ~in the three lower lumbar and upper sacral segments
exceeded the lumbar of such fibers in the internodal and white
rami of higher levels.
400
JOSEPH PICK
When using this material as basis of comparison, it became
obvious that the wide range of variation occurring normally
in the number of myelinated fibers in gray rami, even in the
two sides of the same animal, warrants a greater emphasis
on the presence rather than on the absence of such fibers iii
TABLE 1
Number and size of all myelinated fibers in the individual nerve 6undles of normal
gray rarni communicantes in the lumbo-sacral sympathetic of the cat (18 sides)
FIBERS U P TO
GRAY
PAMUS
NOT DETERMINED
L1
L2
1
1
Range of
number
FIBERS OYER 4.5 JL
4.5 p
Range of
Instances
- 12.5 /L
Instances
Present
Absent
number
Present
Absent
3- 70
2- 72
18
14
..
..
1- 6
2-13
5
4
13
12
3- 65
12
..
2-21
8
8
2
1- 4
1-17
10
10
7
10
1-11
1-10
1- 2
1- 4
11
16
7
5
1
7
7
5
11
L3
..
4l
L4
L5
..
..
L6
L7
..
s2
53
..
1
3
s1
1
5- 86
1-155
15-337
4-393
11-148
5- 96
3-151
15
18
2'
18
23
12
11
9
..
..
..
..
..
..
TABLE
1
6
8
2
Number of large myelinated fibers measuring over 4 . 5 ~and u p to 13.6~~in the
normal internodal rami of the lumbo-sacral sympathetic trunk of the cat
(12 sides)
INTERNODAL
RAMUS
NOT DETEPMINED
RANGE O F NUMBER
OF FIBERS
Ll-LZ
L2-L3
L3-L4
L4-L5
L5-L6
L6-L7
L7-S1
51-s2
52-53
2
2-84
1-12
1- 7
2-18
1-27
2-13
1- 8
1
2-1 1
5
2
2
..
..
..
6
6
INSTANCES
Present
Absent
10
..
3
4
7
12
10
7
1
4
6
3
..
2
5
5
2
4
401
MYELINATED FIBERS IN GRAY RAM1
TABLE 3
Number of large myelinated fibers measuring over 4 . 5 ~and u p to 12.5~in the
individual nerve bundles of normal white rami communicantes in the
lumbo-sacral sympathetic of the cat (12 sides)
WHITE
RAMUS
L1
L2
L3
L4
L5
NOT DETERMINED
RANGE OR NUMBER
O F FIBERS
..
..
3-1 7
2-19
2-28
1-28
1-18
..
1
4
INSTANCES
...........FILLED - 1
FiLLED
Present
Absent
13
15
..
16
..
21
7
1
5
3
f
I3
)~LLZ
19
-12.....
...............................
72-
v/..................115-1
6-
3
0-
2
69-
I
L3
FILLED-(5
FILLED
-0
FILLED-45
FILLED
- 2..
L5
.......................
- ........ 321 - I
................................
..................................
217
- 5
II-
0
8-
0
4-
0
\ b sI
k
.............................
s
3
Fig. 1 The normal content of myelinated fibers in the lumbo-sacral sympathetic
r m i Of cat NO. d (left side). White rami communicantes ascend, gray rami
descend from the sympathetic trunk to the spinal nerves. Small myelinated
fiber8 up to 4 . 5 ~in diameter are indicated in small type, larger fibers i n large
type. Small fibers fill the internodal and white rami; they are accurately counted
in all gray rami. Note the distribution of large fibers: Only 7 fibers in the
5th, 6th and 7th lumbar gray rami; 2 large fibers in the sympathetic trunk
below and none above the 5th lumbar ganglion.
402
JOSEPH PICK
evaluating the results of nerve degeneration experiments.
Furthermore, the individual nerve bundles, especially those
which constitute the 6th and 7th lumbar gray ramus showed
considerable differences in size and fiber constitution. I n any
given ramus it is not always the largest bundle which contains
the highest number of myelinated fibers, in fact, the majority
of large myelinated fibers often travel in a separate bundle.
Obviously, only careful dissection and microscopical examination of all bundles forming a specific ramus will avoid the
pitfall of erroneously diagnosing nerve fiber degeneration
in a gray ramus whose myelinated component was either small
from the beginning, or was packed in a small nerve bundle
which had escaped attention.
TABLE 4
itlyelinated fibers remaining in t h e lower lumbar and upper sacral sympathetic
ram{ a f t e r division of the sympathetic trunk above and below t h e
6 t h lumbar ganglion ( o a t )
RANGE OF NUMBER O F FIBERS
RANUS
Internodal
Gray
L4 - L5
L5 - L6
L6
L6 - L7
L7
L7 - 51
s1
INSTANCES
7
5
7
7
7
6
7
Up to 4.5 p
Over 4.5 p - 12.5LI.
filled
filled
33 - 219
0 - 53
25*- 411
0 - 92
24 - 285
0-21
1-17
0-10
0- 3
0- 5
0- 5
0- 4
Twenty-five fibers in one case only; in all other cases over 200.
T h e result of nerve degeneration experiments
( a ) T h e divisiort of t h e sympathetic t r u n k above and below
t h e 6th lumbar sympathetic gangliort (table 4).
In the lower lumbar and sacral sympathetic t r u n k a considerable proportion of fine myelinated fibers up to 4.5 i~
disappeared after the operation, due to the degeneration of
preganglionic fibers which had been interrupted caudal to
the lower limit of the spinal sympathetic outflow (Langley,
1892; Ranson and Billingsley, '18) ; large fibers, as observed
MYELINATED FIBERS IN GRAY RAM1
403
in the normal (table 2), were either missing o r did not amount
to more than 5 in number.
I n the 6th and 7th lumbar and 1st sacral g r a y rami, on
the other hand, the number of large and small myelinated fibers
remained well within normal range (figs. 2, 3, 4). The effect
of this operation made it obvious that the remaining myelinated fibers in the lower lumbar and upper sacral sympathetic
must have had their cell bodies either in the sympathetic
trunk and/or in the spinal cord or dorsal root ganglia of the
lower lumbar and sacral regions.
( b ) Division of the sympathetic trunk above and below t h e
6th lumbar sympathetic gamglion followed b y the removal
o f the 6th and 7th spinal roots and dorsal root ganglia.
I n one cat the 5th spinal roots and dorsal root ganglioa
w a s also excised and those of t h e 1st sacral in amother
(table 5).
(This series was supplemented by another in which the
lower lumbar and upper sacral spinal roots and dorsal root
ganglia were removed without previous severance of the
sympathetic trunk. The result of these additional experiments were similar to that obtained by the combined operation, and is, therefore, not especially recorded here.)
As observed in the preceding series, there was either
complete or partial degeneration of small myelinated fibers
in the lower lumbar and sacral sympathetic trunk due to
degeneration of preganglionic fibers. The content of small
myelinated fibers up to 4.5~in the two lower lumbar and
1st sacral g r a y rarni was again well within normal range.
Large myelinated fibers over 4.5 p, however, were always
absent in those gray rami, whenever they had been severed
from their corresponding spinal roots and dorsal root ganglia.
The result of this operation indicated that the main bulk
of small myelinated fibers u p t o 4.5 v in the two lower lumbar
and upper sacral gray rami could not have been of spinal
origin, but must have had their source in the gartglia of the
lower lumbar and sacral sympathetic tru& Nevertheless,
the question remained open, whether these fibers were post-
404
JOSEPH PICK
ganglionic axons, or whether they represented the peripheral
processes of afferent cells placed in sympathetic ganglia as
postulated by Dogie1 (1896). This was the more interesting
to decide in view of a variable and limited number of small
myelinated fibers which were left in the sympathetic trunk
below the point of cutting, and which could have represented
either the central processes of afferent sympathetic cells, or
postganglionic axons which had travelled from their cells of
origin in the sympathetic before emerging into a gray ramus
of another segment. The absence of large myelinated fibers
TABLE 5
Myelinated fibers remaining in t h e lower lumbar and upper sacral sympathetic
rami a f t e r division of the sympathetic trunk above and below t h e 6 t h lumbar
ganglion followed b y remozral of both spinal roots and dorsal root ganglia of segments L6,L7 (2 cats), L5,L6,L7 (1 c a t ) and L6,L7,81 (1 cat).
~~
~
RANGE OF NUMBER OF FIBERS
RAMUS
INSTANCES
Internodal
Gray
L4 - L5
L5 - L6
4
L6
L6 -L7
L7
L7 - S1
s1- s2
l
s1
Only when S1 -spinal
4
4
4
4
3
4
4
Up to 4.5 f i
filled
filled
19 - 115
0 - 316
182 - 401
8- 69
88 - 185
7 - 100
Over 4.5 IL
- 12.5 IL
1- 8
2-15
0
0
0
0
0- 3'
0- 1'
roots and dorsal root ganglion intact.
over 4.5 p in the lower lumbar and upper sacral sympathetic
rami pointed to the spinal origin of such fibers at these levels,
although this finding could have been a coincidence (see tables
1-3).
( c ) Division of t h e sympathetic trunk between t h e 2nd and
3rd and between t h e 3rd and 4th lumbar ganglia followed
b y t h e e m i s i o n of both spinal roots and dorsal root
ganglia of the 1st lumbar d o w n t o the 2nd sacral segmemts,
t h e 2nd t o t h e 7th lumbar and of t h e 1st lumbar d o w n t o
t h e 2nd sacral, leauing t h e 5th spinal roots and dorsal
root gangliorn intact.
MYELINATED FIBERS IN GRAY RAM1
405
The effect of the isolation of almost the entire lumbo-sacral
sympathetic from preceding sympathetic and corresponding
spinal levels is illustrated on a specific case (fig. 7). There
was either complete or partial degeneration of small myelinated fibers in the white rami communicmtes and in the
sympathetic trwnk, but the proportion of myelirzated fibers up
to 4.5 p in gray rami remained entirely normal: The 5th lumbar
gray ramus contained 143, the 6th, 310 and the 7th, 419 small
fibers (figs. 8, 9). Had the majority of these fibers been the
peripheral processes of sensory cells placed in ganglia of the
sympathetic trunk, their central processes would have been
present in the adjacent internodal rami of the sympathetic
trunk. This, however, was not the case. There were only
22 small fibers between the 5th and 6th lumbar sympathetic
ganglia, 45 between the 6th and 7th, and 20 between the 7th
lumbar and the 1st sacral. The number of such fibers was even
less in higher levels of the sympathetic trunk (fig. 7).
Therefore, it was concluded that the main bulk, if not all
small myelinated fibers up to 4.5p present in the lumbosacral sympathetic rami of this cat had to be interpreted as
postganglionic arising from ganglion cells of the sympathetic
trunk; some of these fibers issued directly into the gray
ramus, others may have passed up o r down the sympathetic
trunk before emerging into a ramus one or two segments
above or below their level of origin.
Large myelinated fibers measuring over 4.5 I.I in diameter
were absent in all lumbo-sacral sympathetic rami except f o r
one fiber of i'p in the sympathetic trunk between the 5th
and 6th lumbar ganglia, and another in the white ramus
to the 3rd lumbar nerve. This indicated that the few large
myelinated fibers which occur normally in the sympathetic,
had degenerated, because they had been severed from their
trophic center in the spinal cord or dorsal root ganglia. The
spinal origin of large myelinated fibers appeared to be even
more likely, when such fibers measuring from 6 p-10 p (figs.
5, 6) were found at and near the 5th sympathetic segment
of a cat in which only the 5th lumbar and 3rd sacral spinal
406
JOSEPH PICK
roots and dorsal root ganglia had been left intact and the
sympathetic trunk had been severed between the 3rd and 4th
lumbar ganglia.
T h e myelinated fibers ir, %normal gray rarni commzcnicantes
as revealed on serial sections
The result of the study of serial sections is exemplified on
a specific 7th lumbar gray ramus which was sectioned serially
together with the 7th lumbar spinal nerve, the 7th lumbar
sympathetic ganglion and the splanchnic nerve which arose
therefrom. A part of the surrounding psoas muscle and the
lumbar blood vessels were included in the serial sections.
At the spinal nerve, the ramus consisted of 7 medium sized
nerve bundles (fig. 10 at a-g), some of which moved together
(fig. 11) to form larger ones (fig. 12), until the nerve was
formed by two large and two small separate bundles (fig.
13 at h-k) just before reaching the sympathetic trunk. This
series also revealed that small, but distinct nerve bundles
leave and join the ramus along its course. Thus, bundles
a and b (figs. 10,10a, lob) containing 36 myelinated fibers up
to 4 . 5 ~and 54 large myelinated fibers measuring over 4 . 5 ~
and up to 12.5 p entered striated muscle (fig. 11 at a, b) and
could not be detected in any further section through the ramus.
Another nerve bundle containing several large myelinated
fibers approached the ramus communicans (fig. 11at x) and
could be traced as far as the sympathetic trunk. Furthermore,
there was near the lumbar artery an unmyelinated nerve
bundle including also a few myelinated fibers (fig. 12, at
arrow), which was subsequently traced into the adventitia
of this vessel. I n addition, there were 13 large myelinated
fibers which did not form a distinct bundle, but traversed
the entire length of the ramus comunicans and could be
followed across the sympathetic trunk into the splanchnic
nerve as far as the bifurcation of the aorta.
Subsequently, a comparison was made, in this ramus, of
the size and number of myelinated fibers present in a section
MYELINATED FIBERS IN GRAY RAM1
407
which was cut close to the spinal nerve (figs. 10, 10a-lOe),
with another which was cut near the sympathetic trunk (fig.
13, 13h-13k): The number of small myelinated fibers up to
4 . 5 ~decreased from 618-290 from the sympathetic trunk to
the spinal nerve. The reverse was true for the larger fibers:
There were 104 large fibers near the spinal nerve, but near
the sympathetic trunk there were only 34.
Clearly, the microscopical appearance of a cross section
through a ramus communicans depends upon the level at
which the section was taken.
On their way to the spinal nerve, the number of smaZ2
myelinated fibers representing postganglionic sympathetic
axons decreased, because a certain proportion was given of€
as vascular nerves to the lumbar artery, the psoas, spinous
ligaments, and perhaps also as “de-fatiguing” nerves (Orbeli, ’29; Hutter and Loewenstein, ’ 5 5 ) to striated muscle,
before the remaining fibers passed peripherally to sweat
glands and smooth muscle along the spinal nerve. Most of
the large myelilzated fibers either run for a short distance
in the ramus communicans, whereupon they passed directly
to muscle and ligaments of the spine. This course of large
myelinated fibers explains their numerical decrease in the
ramus, when it is traced from the spinal nerve into the
sympathetic trunk and, it may account also for a “slight
twitch of some lumbar muscles, ” ensuing upon electrical
stimulation of the 6th or 7th lumbar gray ramus (Langley,
1892). Or, a very few large fibers may have taken a round
about route: Thus, 3 or 4 large myelinated fibers (fig. 11
at x) issued, say, from the 6th lumbar spinal nerve into
the 6th lumbar ramus communicans and passed through the
sympathetic trunk into the 7th lumbar gray ramus in which
they may have travelled half way before reaching their
destination in striated muscle or ligament. Such a course
would account for the presence of some large myelinated
fibers in an internodal segment and adjacent rami communican t es.
408
JOSEPH PICK
Finally, there were still a dozen large myelinated fibers to
explain which passed from the spinal nerve through the
ramus communicans, sympathetic trunk and splanchnic nerves
as far as to the aorta and its branches.
The innervation of the origin of the inferior
meseateric artery and aortic bifurcation
At first, all myelinated neurons in lumbar splanchnic nerves
were considered to serve the innervation of the intestine :
Small' myelinated fibers were regarded, in part, as preganglionic, in part, as postganglionic and large myelinated fibers
were looked upon as afferent (Ranson and Billingsley, '18).
However, the question had to be raised as to whether the
lumbar splanchnics, perhaps the large myelinated fibers contained therein, innervate some vaso-sensitive zones of the
abdominal aorta. This possibility had to be considered, first,
because fine branches of the lumbar splanchnics were observed
to enter the wall of the aortic bifurcation and the origins
of the mesenteric arteries of the cat and of man, and secondly,
because of "slight changes in respiration and blood pressure )'which ensued upon stimulation of lumbar sympathetic
rami (Langley, 1892; Kuntz, ,51).
Using the method which Moissejeff ( '27) employed to
elicit the carotid sinus reflex, an attempt was made to alter
cardiovascular and respiratory activities by the distension
of the vascular cul de sac made of the aorta and inferior
mesenteric artery. However, this maneuver produced only a
slight fall in blood pressure, but no change in respiration or
heart rate.
Subsequently, a search was made for histological evidence
of stretch receptors in the abdominal aorta. Thus far, the
study of serial sections of the origins of the celiac, and
mesenteric vessels and aortic bifurcation revealed small nerve
bundles entering the adventitia of these blood vessels, but
nerve endings which could be interpreted as stretch receptors
as they were described by DeCastro ('28) and by Sunder-
MYELINATED FIBERS IN GRAY RAM1
409
Plassmann ('30) in the carotid sinus region, could not be
detected.
These preliminary studies together with previous observations (Langley, 1892; Heymans, '29 ; Kuntz, '51) indicated
that vaso-sensitive zones about the aorta either do not exist
at all, or if they do, their significance must be only slight.
DISCUSSION
Considering all evidence, it appears that the main bulk of
myelinated fibers measuring u p t o 4 . 5 ~ 'which are present,
especially in the gray rami of the plexus to the hindlimb,
are postgafiglionic azons with their cells of origin in the
ganglia of t h e sympathetic trunk. The few large myelinated
fibers measuring over 4.5 p and up to 12.5 F, arise from the
spinal cord and dorsal root ganglia of levels corresponding o r
adjacent to those at which these fibers enter the g r a y rami.
Large fibers are essentially somatic to lumbar muscle and to
the spine. A few of these large fibers pass on into the
splanchnic nerve and are tentatively interpreted as supplying
the wall of the abdominal aorta and the adjacent origins of
mesenteric arteries.
The findings of this inquiry are nearly in full agreement
with those reported by Langley (1892, 1896). This author,
however, placed the cells of origin of a few myelinated fibers
in the dorsal root ganglia 5 or 6 segments higher than those
at which these fibers pass through the gray ramus. This
statement may be due to the unsatisfactory method of determining the degree of nerve degeneration by teasing apart
the individual fibers with a pair of needles.
On the other hand, the result of this investigation differs,
in several points, from the interpretation offered by Kuntz
and Farnsworth ('31) and by Kuntz ( '51). These authors
considered only a small proportion of the finest myelinated
fibers, not exceeding 2 . 5 ~as postganglionic, and see the
principal significance of myelinated fibers in gray rami as
concerned with the conduction of pain-impulses from the
410
JOSEPH PICK
blood vessels of the limbs along the route quoted in the introduction of this paper.
I n this investigation, however, no evidence could be obtained
which would confirm the existence of such pathways.
These authors arrived at their conclusions, perhaps, because
they used the proportion of myelinated fibers in the normal
corresponding gray ramus as yardstick for evaluating the
results of their degeneration experiments. This indicates that
they were, perhaps, not fully aware of the wide differences
which can exist in the number of these fibers in the two
sides of one and the same animal, as well as of the changes
in the microscopical consitution of one and the same ramus as
seen on serial sections.
Therefore, the existence of pain-carrying fibers as suggested
by Kuntz ('51) is questionable, and this even more so in view
of the conflicting clinical evidence.
It is true, pain in the hand and foot of our patients could
sometimes be relieved by surgical interruption or chemical
blocking of the sympathetic, and pain could be elicited in
patients by stimulation of the sympathetic (Echlin, '49 ;Kuntz,
'51). Notwithstanding these observations, sympathectomy
has failed to relieve the pain in many other instances. On
clinical grounds, one must, therefore, regard the existence
of accessory conduction of pain from the blood vessels of
the limbs across the sympathetic, as a matter of theory rather
than of fact. (Leriche, '39; White, '54).
There remains briefly to comment on the few large myelinated fibers in the lumbar splanchnics which according to
Langley (1892) serve a "special function."
I n this investigation only scanty evidence could be brought
forth to suggest the existence of a vasomotor reflex, elicited
from vasosensitive areas in the abdominal arteries and mediated through lumbar splanchnic nerves. Neither could Langley (1892) and Kuntz ('51) observe in the cat more than
slight changes in circulation and respiration upon stimulation
of the lumbar sympathetic, nor could Heymans ( '29) working
MYELINATED FIBERS IN GRAY RAM1
411
with the dog, produce any such changes at all upon manual
occlusion of the abdominal aorta or celiac artery.
I n birds and aquatic mammals, on the other hand, such a
reflex might be brought into play by the congestion of blood
in the abdomen upon rapid change in altitude. This might
be the mechanism underlying the sudden and complete vasoconstriction of the intestine and hindlimbs, associated with
a sharp fall in heart rate, but little change in blood pressure,
ensuing in these animals during diving (Irving, Scholander
and Grinell, '42).
Still, further evidence is necessary to confirm that such
a reflex - fully developed in diving animals, but vestigial in
terrestrial forms -is really initiated by the distension of
large abdominal arteries and mediated through the lumbar
splanchnic nerves, perhaps through the large myelinated fibers
contained therein.
SUMMARY
An investigation was made of the source and distribution of
the myelinated fibers in the gray rami communicantes of the
lumbo-sacral sympathetic in the cat.
The range of variation occurring in the size and number of
all myelinated fibers in gray, and of the larger myelinated
fibers in the white and internodal rami of the sympathetic
trunk was determined in 1 2 sides of normal cats.
Nerve degeneration experiments were carried out unilaterally in 17 cats, by division of the sympathetic trunk
at the 6th lumbar ganglion with and without subsequent
removal of both spinal roots and dorsal root ganglia of lower
lumbar and upper sacral segments; by removal of lower
lumbar and upper sacral spinal roots and dorsal root ganglia
without division of the sympathetic trunk; by severance of
the sympathetic trunk at upper lumbar levels followed by the
excision of both spinal roots and dorsal root ganglia of all
lumbar and two upper sacral segments. The time allowed for
degeneration of sympathetic nerves ranged from 31-98 days,
and that of spinal nerve roots from 19-50 days. The sym-
412
JOSEPH PICK
pathetic rami of normal and experimental animals were
stained with 1%osmium tetroxide. Counts and measurements
of myelinated fibers in sympathetic rami were made on prints
of enlarged photomicrographs taken of representative sections. I n two cats serial sections through the spinal nerve,
ramus communicans, sympathetic trunk and splanchnic nervq
of lower lumbar and upper sacral segments were taken and
stained with 1% osmium tetroxide; the number and size of
myelinated fibers were determined in the same manner as in
the first series.
I n three cats the origins of the mesenteric arteries and the
aortic bifurcation were examined histologically for the presence of stretch receptors using the silver impregnation method
for staining.
I n three cats a search was made for vaso-sensitive zones
by distending the origin of the inferior mesenteric artery
and by taking simultaneously blood pressure readings from
the carotid artery.
The highest proportion of myelinated fibers is present in the
lower lumbar and upper sacral gray rami.
The number of these fibers have a wide range of variation
both from case to case and in the two sides of the same cat.
The changes of the histological constitution at various levels
of one and the same ramus is demonstrated on serial sections.
The majority of myelinated fibers measuring up to 4 . 5 ~
in diameter, represents postganglionic axons with their cells
of origin in the ganglia of the sympathetic trunk. Larger
fibers are either absent or amount only to a few, with their
trophic centers in the spinal cord and dorsal root ganglia of
the same or adjacent segments at which they enter the gray
ramus. Large myelinated fibers supply lumbar muscle and
ligaments of the spine. A few large fibers which pass from
the gray ramus into the splanchnic nerve may be concerned
with the mediation of a vasomotor reflex arising from vasosensitive zones in the abdominal arteries.
No evidence could be obtained that myelinated fibers in
gray rami of the lumbo-sacral plexus are funneled into the
MYELINATED FIBERS I N GRAY RAM1
413
sympathetic trunk and upper lumbar rami communicantes,
to serve the conduction of pain impulses from the blood
vessels of the hindlimb.
LITERATURE CITED
CAJAL, R. S. Y, 1911 Histologie du systAme nerveux de l’homme et des
vert6br6s. Tome 11: 1-993. transl. by Azoulay, L., A. Maloine,
Paris.
CARPENTER,
F. W., AND J. L. CONEL 1914 A study of ganglion cells in the
sympathetic system, with special reference to intrinsic sensory neurones.
J. Comp. Neur., 8 4 : 269-279.
CASTRO,
F. DE, 1928 Sur la structure e t l’innervation du sinus carotidien de
l’homme et des mammifhres. Nouveaux faits sur l’innervation e t la
fonction du glomus caroticum 6tudes anatomiques et physiologiquea.
Trav. Lab. Recherch. Biol., Z.5: 331-380.
CYON, E. DE, UND C. LUDWQ1866 Die Reflexe eines der sensiblen Nerven des
Herzens auf die der motorischen der Blutgefasse. Ber. ii.d. Verh.d.
I(. SIehs. Gesell. d. Wiss. Leipzig, 18: 307-328.
DOQIEL, A. S. 1896 Zwei Arten sympathischer Nervenzellen. Anat. Anz., 1 2 :
679-687.
ECHLIN,F. 1949 Pain responses on stimulation of the lumbar sympathetic
chain under local anesthesia. J. Neurosurg., 6: 530-533.
HEYMANS,
C. 1929 Le sinus carotidien et les autres zones vaso-sensible r6flexoghnes; leur r6le en physiologie, en pharmacologie et en pathologie.
1-121, H. K. Lewis, Lonvain, Paris, Londres.
HUTTER,0. F., AND W. R. LOEWENSTEIN
1955 Nature of neuromuscular
facilitation by sympathetic stimulation in the frog. J. Physiol., 130 .559-571.
IRVINQ,L., P. F. SC’HOLANDER
AND S. W. GRINELL 1942 The regulation of
arterial blood pressure in the seal during diving. Am. J. Physiol.,
136: 557-566.
JOHNELS,A. G. 1955 Suppression of costaining of non nervous tissue in
protargol techniques. Stain Technol., 30 : 169-172.
JOHNSON,
S. E. 1921 An experimental study of the sacral sympathetic trunk
of the cat with special reference to the occurrence of intrinsic commissural neurones. J. Comp. Nenr., 33: 85-104.
KUNTZ,A., AND D. I. FARNSWORTH
1931 Distribution of afferent fibers via
the sympathetic trunks and gray communicating rami to the brachial
and lumbo sacral plexuses. J. Comp. Neur., 53: 389-399.
KUNTZ, A. 1951 Afferent innervation of peripheral blood vessels through
Sympathetic trunks. South. M. J., 4 4 : 673-678.
LANQLEY,
J. N. 1892 On the origin from the spinal cord of the cervical and
upper thoraoic sympathetic fibres, with some observations in white
and grey rami communicantes. Philos. Trans. Roy. SOC. London,
183-B 85-124.
414
JOSEPH PICK
LANGLEY,
J. N. 1896 Observations on the medullated fibres of the sympathetic
system and chiefly on thoae of the grey rami communicantes. J.
Physiol., 20 : 55-76.
1904 On the question of commissural fibres between nerve cells
having the same function and situated in the same sympathetic
ganglion, and on the function of postganglionic nerve plexuses. J.
Physiol., 31 : 244-259.
LERICHE,R. 1939 The surgery of pain. Transl. by Young, A, 1-512, Williams
and Wilkins, Baltimore.
MOISSEJEFF, E. 1927 Zur Kenntnis des Carotis sinus reflexes. Z. exp. Med.,
5 3 : 696-704.
MULLER,L. R. 1909 Studien uber die Anatomie und Histologie des sympathischen Grenzstranges insbesondere iiber seine Beziehungen zu dem
spinalen Nervensysteme. Verh. Kongr. Inn. Med., 26 : 658-681.
NEVIN, S. 1930 Degeneration changes after unilateral lumbar sympathectomy,
with general observations on the nerve-fibre constitution of peripheral
nerve and nerve-roots. Quart. J. Exp. Physiol., 20: 281-297.
NONIDEZ,J. F. 1939 Studies on the innervation of the heart. Am. J. Anat.,
65: 361-401.
ORBELI, L. A. 1929 On the trophic nerves to skeletal muscles. Bull. Battle
Creek Sanat. and Hosp. Clin., 24: 421-422.
PAARMANN,
H. F. 1950 Zur Frage der afferenten vegetativen Fasern. Arch.
Psych. u. Nervenkrankh., 185: 13-21.
PICK,J., AND D. SHEEHAN1946 Sympathetic rami in man. J. Anat., 80:
12-20.
RANSON,S. W. 1918 An introduction to a series of studies on the sympathetic
nervous system. J. Comp. Neur., 29: 305-312.
RANSON,S. W., AND P. R. BILLINQSLEY1918 The thoracic truncus sympathicus,
rami communicantes and splanchnic nerves i n the cat. J. Comp. Neur.,
29: 405-439.
SHEEHAN,
D., AND J. PICK 1943 The rami communicantes in the Rhesus
monkey. J. Anat., 7Y: 125-139.
SUNDER-PLASSMANN,
P. 1930 Untersuchungen uber den Bulbus carotidis bei
Mensch und Tier in Hinblick auf die “Sinus Reflexe” nach H. E.
Hering ; ein Vergleich mit anderen Gefasstrecken ; die Histopathologie
des Bulbus carotidis; das Glomus caroticum. Z. f. Anat. u. Entw.,
93: 567-622.
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71: 1-23.
PLATES
PLATE 1
EXPLANATION OF FlGURES
Division of the lumbo-sacral sympathetic trunk above and below the 6th
lumbar ganglion leaves the appearance of the gray rami below the point of
cutting unchanged (cat; osmium tetroxide; obj. R. Winkel Apochromat 3 mm;
C. Zeiss Complanat-Ocular 3; enlarged to the scale as indicated on the plate).
2 Large upper bundle of 7th lumbar gray ramus commuiiicants contains
325 myelinated fibers measuring less than 4.5 p in diameter.
3
Small lower bundle of the same 7th lumbar gray ramus has 23 myelinated
fibers up t o 4 . 5 ~and three myelinated fibers measuring 6 p in diameter.
4 One bundle of the 1st sacral gray ramus comniunicans contains 40 myelinated
fibers measuring less than 4 . 5 ~and 4 niyelinated fibers of 6,a-lOr
diameter.
in
Division of the sympathetic trunk between the 3rd and 4th lumbar ganglia
followed by the removal of both spinal roots and dorsal root ganglia of the
1st lumbar down to the 2nd sacral segments, leaving the 5th lumbar spinal roots
and root ganglion intact. (Cat no. 18; osmium tetroxide; obj. R. Winkel 3 m m ;
C. Zeiss Complanat-Ocular 3 ; enlarged t o the scale as indicated on the plate.)
Note the remaining large myelinated fibers near the 5th lumbar segment.
5
The small lower bundle of the 5th lumbar gray ramus has 111 fibers up to
4.5 p and 5 large fibers measuring 6p-10 p in diameter.
6
The sympathetic trunk between the 5th and 6th lumbar ganglia shows marked
degeneration of small fibers, but contains 8 myelinated fibers of 7.5 P-10 & i n
diameter
.
416
MYELINATED FIBERS IN GRAY B A M I
PLATE 1
JOSEPH P I C K
417
PLATE 2
EXPLANATION OF' FIGURES
The effect of the division of the sympathetic trunk between the 2nd and 3rd
lumbar ganglia followed by the removal of both spinal roots and dorsal root
ganglia from the 1st lumbar down t o the 2nd sacral segments inclusive (cat
No. 17):
Note the normal number of small myelinated fibers up to 4 . 5 ~in the gray
rami communicantes, but these fibers are reduced to a few in the sympathetic
trunk and white rami below the point of cutting. Large myelinated ar e
absent, except for one fiber of 7 p between the 5th and 6th lumbar ganglia
and one fiber in the 3rd lumbar white ramus. (Small fibers are indicated
in small type, large fibers in large type.)
The intermediate bundle of the 6th lumbar gray ramus communicans contains
203 myelinated fibers measuring up t o 4.5 p in diameter (cat No. 17).
The upper bundle of the 7th lumbar gray ramus communicans contains
374 fibers measuring up to 4.5 p in diameter. (Cat No. 17; osmium
tetroxide; obj. R. Winkel Apochromat 3 mm; C . Zeiss Cornplanat-Ocular 3 ;
enlarged to scale as indicated on the plate.)
418
MYELlNATED FIBERS I N GRAY E A M I
PLATE 2
JOSEPH PICK
419
PLATE 3
EXPLANATION OF FIGURES
The myelinated fibers i n a normal 7th lumbar gray ramus communicans as
revealed on serial sections. (Cat No. 31; osinium tetroxide; obj. R. Winkel.
Apochromat 25 mm; C. Zeiss Complanat-Ocular 3.)
A. Four sections of this series illustrate the differences i n the appearance of
one and the same gray ranius when it is traced from the spinal nerve to the
sympathetic trunk.
10 Close to the spinal nerve, the ramus consists of 7 medium sized nerve
bundles (a-g)
.
11 Bundles a and b consisting mostly of large niyeliiiated fibers enter striated
muscle; other bundles ' ' sprinkled' ' with niyelinated fibers niove together ;
a new bundle x joins the ramus.
12
The ramus is formed by two large nerve bundles containing numerous
myelinated fibers. Note a t arrow, a n additional small nerve bundle rtpproachi n g the artery, and another minute heavily myelinated bundle a t y.
13
Near the sympathetic trunk, the rainus coiisists of two large and two small
nerve bundles (h-k) each containing many myeliriatrd fibers.
420
MYELINATED FIBERS I N GRAY RAM1
TABLE 3
J O S E P H PICK
421
PLATE 4
EXPLANATION OF FIGURES
The myelinated fibers in a normal 7th lumbar gray ramus communicans as
revealed on serial sections. (Cat No. 31; osmium tetroxide; obj. R. Wiiikel;
C. Zeiss Complanat-Ocular 3 ; enlarged to the scale indicated on the plate.)
B. The myelinated fibers in the individual nerve bundles a-e of the ramus at
the spinal nerve (fig. 10) are compared with the myelinated component of the
individual bundles h-k of the same ramus at the sympathetic trunk (fig. 13).
The myelinated fibers i n the nerve bundles a-e comprising the ramus near
the spinal nerve (bundles f and g of fig. 10 not included):
10a contains 21 fibers up to 4.5 p and 36 over 4.5 1.1 and up to 12.5 p.
10b contains 15 fibers up to 4.51.1 and 18 fibers over 4.51.1 and up to 1 2 . 5 ~ .
1Oc contains 13 fibers up to 4.5 p and 1 fiber measuring 7.5 P.
10d contains 40 fibers up to 4.5 p and 1 3 fibers over 4.5 p and up to 7.5 p.
1Oc contains 28 fibers up to 4.5 p and 7 fibers over 4.5 p and up to 7.5 p.
The myelinated fibers in the nerve bundles 11-k coinprisilig the ramus near
the sympathetic trunk.
13h is the principal bundle of this ramus arid contains 386 fibers up to 4 . 5 ~
and 13 large fibers measuring over 4.5 p and up to 12.5 p ; these large fibers
run to the aortic bifurcation by wag of the splanchnic nerve.
13i contains 164 fibers up to 4.5 p and 7 fibers over 4.5 1.1 and up to 12.5 p.
13j contains 39 fibers up to 4.5 p arid 9 fibers over 4.5 p and up to 7.5
p.
13k contains 29 fibers up t o 4 . 5 ~and 4 fibers over 4 . 5 ~and up to 7 . 5 ~ .
422
PLATE 4
M Y E L I N A T E D PISEItS I N (?BAY 1CAMl
JOSEPH P I C K
423
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