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seems to receive fibers which pass from a group of cells, called Clarke's vesicular column (Fig. 170). The fibers of which the direct cerebellar tract is composed are believed to pass to the superior vermiform process of the cerebellum directly—i. e., without the intervention of any nodal masses of gray matter.

The course of these fibers through the restiform body of the medulla and their ultimate termination have been considered in the previous section.

The POSTERO-INTERNAL, or GOLL'S COLUMN, is composed chiefly of long and short fibers derived from the posterior horn of gray matter and the gray commissure. It is probably associated with the conduction of tactile sensations from the legs upward to the brain.

The POSTERO-EXTERNAL, or BURDACH'S COLUMN, is composed (1) of fibers derived from the posterior roots of the spinal nerves passing inward to join the posterior horn, (2) of fibers that convey tactile impressions from the upper limbs to the brain; and (3) possibly of commissural fibers which connect the posterior horns of the various spinal segments.

Ott believes that all the sudorific and inhibitory fibers of the spinal cord decussate, as well as the motor, sensory, and vaso-motor fibers. He places the tract of the sudorific and inhibitory fibers in the lateral column of the cord, and also some fibers of sensation. He supports the view that the posterior columns are physiologically associated with the transmission of tactile sensations. In reference to the function of the gray matter as a medium of conduction, this experimenter differs from the view of Schiff that afferent impulses may be carried in all directions. It is probable, however, that the paths for reflex action are in the gray matter. He disputes the statement of Brown-Séquard that the anterior columns carry fibers of sensation.

The late researches of Starr in reference to the course of the sensory tracts partly sustain the opinion of Schiff, deduced from experimentation upon animals, viz., that the sensations of touch and of the muscular sense pass upward along the

posterior columns of the cord, and that the sensations of temperature and of pain travel either in the spinal gray matter or the direct cerebellar columns.

He believes that the columns of Goll transmit the impressions of the muscular sense pertaining to the legs, and those of Burdach impressions of a similar kind from the upper extremities.

He excludes, however, the view that the direct cerebellar columns carry sensations of pain or of temperature, because these tracts do not extend below the first lumbar segment and because they end in the cerebellum. Lesions of this ganglion have never been shown to cause defective appreciation of pain or of temperature. He therefore places the paths of conduction of these two varieties of sensations in the spinal gray

matter.

Respecting the function of the direct cerebellar columns, this author advances a hypothesis that centripetal impulses from the organs within the great cavities of the trunk are conveyed by these columns to the cerebellum and excite (in the reflex centers of this ganglion) the impulses necessary to their normal functions. He supports this view from three standpoints, as follows:

1. An anatomical one, because the limits of the direct cerebellar columns coincide with the entrance into the cord of the nerves associated with the thoracic and abdominal viscera.

2. Because lesions of these columns are attended with irregular action of the functions of the viscera; as, for example, gastric crises and habitual constipation.

3. Because lesions of the cerebellum have been shown to give rise to functional disturbances of the abdominal viscera ; such as indigestion, vomiting, obstinate constipation, polyuria, albuminuria, etc.

Schultze has carefully studied the results of five cases of compression myelitis with special reference to the secondary degeneration, which was thus induced within the motor and sensory spinal tracts. His published conclusions regarding the sensory tracts may be summarized as follows:

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1. Degeneration of the posterior columns was of the ascending type, and was confined to the columns of Goll when all the nerves below the eleventh dorsal were severed from their indirect connection with the brain through the cord.

2. That long and short fibers exist in the posterior colThe longest centripetal fibers of the spinal cord lie in the columns of Goll in its inner and posterior part.

umns.

3. That the fibers for the sciatic nerves lie nearest to the median line and farthest back in Goll's columns. That those of the crural nerves are packed next to these, and bound there both anteriorly and laterally. Finally, that the dorsal nerves fill up the remainder of Goll's column and a part of Burdach's column.

4. The short fibers of Goll's column probably end in the spinal segments. The long fibers are prolonged to the medulla. 5. Some fibers of the posterior nerve roots descend after entering the cord for a distance of two or three centimetres.

6. He places the anterior limits of the direct cerebellar columns farther forward than Flechsig, and states that they reach the point where the fibers of the anterior nerve roots escape.

7. The columns of Burdach contain all the fibers which enter the cord from the posterior roots of the cervical nerves, as well as some from the dorsal nerves.

8. The fibers of the direct cerebellar appear to undergo complete degeneration only after a lesion which lies above the last dorsal segment.

Much of our knowledge of the course of fibers within the spinal cord is no longer speculative. Flechsig has shown that definite tracts of fibers within the spinal cord are developed at different periods, as the cut introduced (Fig. 170) clearly demonstrates, and also that the relative proportion of motor fibers within the direct and crossed pyramidal fasciculi varies with individuals.

We know also that secondary degeneration of nerve-tracts occurs when they are cut off from their so-called "trophic centers" by traumatism or disease-processes. This degenera

tion always (?) progresses in the direction of the currents that are conveyed by the fibers whose nutrition is affected; hence it progresses downward in the motor tracts and upward in the sensory tracts.

Finally, experimental physiology has now determined many facts with an approach to accuracy that were long in dispute, and has thus aided us in properly interpreting symp

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FIG. 170.-A diagram illustrating the development of the different systems of fibers in the spinal cord. (Flechsig.)

I, section at level of third cervical nerves; II, at level of fifth cervical; III, at level of sixth dorsal; IV, at level of fourth lumbar nerves; 1, principal mass of anterior columns; 2, Burdach's columns; 3, lateral columns; 4, lateral boundary of gray substance; 5, columns of Goll; 6, direct cerebellar columns; 7, crossed pyramidal columns; 7', Türck's columns; v, anterior roots. Note that Türck's columns disappear in IV; that Goll's columns increase in size from below upward; that the direct cerebellar columns appear in III, and increase in size in II and I; that the crossed pyramidal columns reach the surface in IV; and that the shape of the gray substance differs in all the sections.

toms referable to spinal disease. We are now enabled to state positively that the "columns of Goll and Burdach," as well as the "direct cerebellar column," conduct centripetal or sen

1 Spitzka advances some pathological observations to prove that this rule has some apparent exceptions.

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sory impulses, while the "columns of Türck" and the "crossed pyramidal tracts" conduct centrifugal or motor impulses. Some portions of the spinal cord are, however, still in dispute, because their special functions are not as yet definitely ascertained.

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FIG. 171.-Diagram of a transverse section of spinal cord in upper half of dorsal

region. (Flechsig.)

c, anterior commissure; de, fibers which pass from the vesicular column of Clarke (vc) to the direct cerebellar tract; P, posterior horn; Pt, crossed pyramidal column; T, direct pyramidal columns; dr, direct cerebellar tract; ar, internal part of anterior root zone; ar', external part of same; pr, posterior root zone; G, columns of Goll; fr, reticular formation of spinal cord; a, anterior horns.

The cut of Flechsig's now introduced will enable you to grasp the general direction and distribution of some of the fibers of the spinal cord. It shows (1) the cut ends of the fibers which make up the mass of the various columns, and (2) the course pursued by the motor and sensory fibers which join the cord at the level of the section. Although this cut is purely diagrammatic, it is admirably devised to bring out certain salient points in spinal architecture, to which reference will be made later. The descriptive text of the cut will render it intelligible to the reader.

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