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No. 10.] 589

131. The Spino-Bulbar Tracts.

Further Contributions to the Theory o f the Sensory Dual Innervation o f the Viscera.

(Preliminary Report)

By Masaru KURu and Naoyuki IsIDA.

Surgical Clinic of Kanazawa University School of Medicine.

(Comm. by H. SHIOTA, M.J.A., Dec. 12, 1952.)

Since all the hollow viscera are provided with functions in two diagonal directions-contraction and distension--and the extreme in one direction should be replaced by function in the other, a dual mechanism is inevitable in their nervous control. In fact, in the centrifugal half the dual innervation of the viscera was elucidated by Langl eyl~ long years ago, and Ishikawa~~ and his collaborators have endeavoured to prove it in the centripetal half too.

In the previous communication one of us (M . K .3)) has pointed out the existence of two categories of centripetal fibers between the inferior part of the spinal cord and the medulla oblongata, which may participate in the mediation of the visceral sensations from the pelvic cavity, the one (the pelvic vagits) being the protoneurons directly connecting the endings in the pelvic organs with the grey substance lateral to the ala cinerea (iuicl eas paraalaris) having their nerve-cells in the posterior roots ganglia of the sacral cord, and the other (the sacro-bulbar tract) being the deuteroneurons originating in the sacral cord and ascending in the lateral fascicle to end in part of the medulla analogous or closely adjacent to the termination of the former.

These evidences concerning the sensory dual innervation of the pelvic viscera suggest the existence of analogous relation through- out the whole viscera. Now, since in the conduction of visceral sen- sations from organs in the thoracic and abdominal cavities the par- ticipation of the vagus nerve is indisputable and since the corre-

Fig. 1. Diagram illustrating the double section experiment in dog. With the transection of the inferior spinal segment (1) the degenera- tion of the sacro-bulbar tract is caused (2).

After the disappearance of the Marchi-granules related to this degeneration on the 30th day from

the first operation a herriisection is added at the lowest level of the cervical cord O. The degenerated fibers traceable in the medulla on the side of hemisection 10 days after the second operation (4) are originated in the part of the cord between both lesions, i. e., in the th~~raco- lumbar division. Marchi-granules are illustrated with dotted lines.

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590 M. Krnw and N. ISIDA. [Val. 28, spondence between the sensory portion of the vagus nerve and the pelvic vagus is clear with our previous investigations, the assump- tion is highly probable, that the other category of sensory fibers in the spinal cord participating in the central mediation of visceral sensations from the thoracic and abdominal cavities shoud take an analogous course to that of the sacro-bulbar tract.

With this possibility in view we carried out following experi- ments in dogs (Fig. 1).

1) In one group a trans-or hemisection of the spinal cord was performed at the lowest level of the lumbar segment. Dogs were allowed to live 1--2 weeks. The ascending degenerations in the spinal cord and medulla were traced in Marchi preparations; the ex- istence of sacro-bulbar tract and pelvic vagus could be demonstrated in this animal too. The site of their endings (nucleus paraalaris) were found to be precisely analogous to that in cat, we noted it in detail.

2) The second group of dogs, on which the transection was made in the inferior part of the lumbar segment, was allowed to survive longer, and a second operation-hemisection-was performed at the lowest level of the cervical cord on the 30th to 40th day from the first operation. On the 10th day from the second opera- tion, they were sacrificed and the ascending degenerations were ex- amined with Marchi serial sections. Since we know most of Marchi granules of the fine calibrated fibers disappear within 30 days in

Fig. 2. (a) Photomicrogram showing the lesion (hemisection) in the 7th cervi- cal segment in a dog of double section experiment. The lateral fascicle and the posterior horn of one side (^) (on the right in the figure) are completely destroyed.

The lesion extends partially towards the posterior funiculus and the anterior fascicle. The triangular degeneration occuppying the middle-most part of the both posterior funiculi () is caused by the previous transection in the 7th lumbar seg- ment. (b) A conspicuous mass of fine degenerated fibers (j) emerging from the restiform body (Cr) and occupying the paraalar nucleus (Npa) are visible almost exclusively on the side of the cervical hemisection (on the right half of the figure).

They correspond to the lumbo-and thoraco-bulbar tracts. Ac, ala cinerea; Fs, solitary fascicle. Marchi-stain, 50 ~~ thick.

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No. 10.] The Spino-Bulbar Tracts. 591

these animals, the degeneration of the intrabulbar part of the sacro- bulbar tract, which is mainly composed of fine medullated fibers, is no more traceable at the time of the examination (in the left half of Fig. 2. (b)) and the conspicuous Marchi-granules found exclusively on the side of hemisection (in the right half of the same Fig.) in the grey substance lateral to the ala cinerea (nucleus paraalaris) can be concluded to have originated in parts of the spinal cord situated be- tween both lesions. In other words, these fibers represent the thoracic and lumbar equivalents of the sacro-bulbar tract. We wish to denominate these newly demonstrated connections in the lateral fascicle between the thoracic and lumbar cord and the paraalar nucleus of the medulla "the thoraco-and lumbo-bulbar tracts".

Since a number of peripheral viscerosensory fibers is known to be contained in both splanchnic nerves taking the course opposite to the visceromotor fibers, the neuronal connections of these peripheral viscerosensory fibers in the splanchnics to the above mentioned thoraco-and lumbo-bulbar tracts is extremely probable. To demon- strate these connections we added following experiments.

3) In the 3rd group of dogs a longitudinal section of the lat- eral column was performed along the inferior one-third of the thoracic cord (where the major splanchnic nerve is connected with the spinal cord) and after 10 days the ascending degenerations were traced in Marchi preparations precisely (Fig. 3).

Analogous to dogs of the 2nd group an abundant mass of Marchi- granules was traced in the paraalar nucleus on the side of lesion which has ascended in the same part of the lateral fascicle as in both previous experiments.

The result of these experiments may be mighty enough to con- vince the existence of the sensory dual innervation for the abdomi- Fig. 3. (a) Photomicrogram showing the depth of lesion

section experiment of the lateral column of a dog. (b) The thoraco-bulbar fibers (Tthb) in the medulla of the same dog.

viations consult the note of Fig. 2. March-stain; 50 µ thick.

in the longitudinal degenertion of the As to other abbre-

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592 M. KURD and N. ISIDA. [vol. 28,

nal and thoracic organs too; in other words, the vagus nerve on one hand and the thoraco-and Jumbo-bulbar tracts on the other are shar- ing the sensory innervation for organs in the thoraco-abdominal cavity (Fig. 4).

Conclusion: The anatomical evidence of the sensory dual in- nervation of the viscera is brought forth. It is provable not only for organs in the pelvic cavity, but also for those in the thoracic and abdominal cavities. As we described in the previous communi- cation, the central mediation of the visceral sensations from organs inside the pelvic cavity is partaken by fibers in the middle-most portion of the posterior f uniculus (pelvic vagus) on one hand, and in the special group of fibers in the anterolateral fascicle (sacro- bulbar tract) on the other. In the mediation of the visceral sen- sations from organs in the thoracic and abdominal cavities, the par- ticipation of the vagus nerve is well known. Here are described newly elucidated components of the anterolateral fascicle, which originate in the thoracic and lumbar segments, accompany the sacro- bulbar tract in the cord and terminate almost in the same part of the medulla, where the latter terminates. For these connections

we propose the name "lumbo-and thoraco-bulbar tracts". The sacro-, Jumbo-and thoraco-bulbar tracts are the constituents of the spino-bulbar tracts (endogeneous connection between the cord and medulla) and may form the main centripetal pathways between the autonomic (inclusive of the vasomotor) centres of the spinal cord and the medulla.

The expences for this work were defrayed by a grant for the scientific research from the Department of Education.

Fig. 4. Diagram showing the sensory dual innervation of the viscera in man, represent- ing the thoraco-abdominal organs with the stomach, and the pelvic organs with the rectum. The vagus and the pelvic vagus are illustrated with broken lines and the sacro-and thoraco-bulbar tracts as well as their peripheral connections with full lines.

The ipsilaterally ascending branch of the sacro-bulbar tract is completely omitted, and the contralaterally ascending branch of the thoraco-bulbar tract is interrupted halfway.

References.

1) Langley, L. M.: Autonomic nervous system. Cambridge 1921.

2) Ishikawa, H.: Reports of the Scientific Society of Japan, 2, 333-349 (1926) (In Japan.).

3) Kuru, M.: Japan. J. Physiol., 1, 240-253 (1951).

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