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FIG. I. Cross section of normal muscle. FIG. II.-Simple degenerative atrophy of muscular fiber. FIG. III.- Fatty infiltration and degeneration of muscular fiber. FIG. IV. Destruction of antero-lateral group of ganglion cells of anterior cornua in grey matter of spinal cord. The ganglion cells to the left (antero-median) are intact, while the antero-lateral have been replaced by cicatricial tissue. (After Wm. C. Krauss.)

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The piton progress of the disease

may be marked by, intervals of apparent
cessation, which may last for weeks,
months, or even years. Again, there
are exacerbations, in which muscles or
groups of muscles are almost completely.
paralyzed in a short time. The average
duration of this disease is from three to
five years. Sometimes cases run a rapid
course, and are at an end in one year;
again, the disease may continue ten or
twelve years without producing death.
One case coming under my observation
dated back fourteen years, and when seen
by me, the patient was able to perform
most of the ordinary movements of health.

Pathological Anatomy. - The patholog-

ical changes on post-mortem examination

will be found, in the main, limited to (1)

the spinal cord, (2) the nerve trunks and

peripheral branches, and (3) the muscles.

The wasting of the muscles is even

more noticeable than before death. They
will be found shrunken, soft, pale in
color, and not infrequently streaked with
light strips of tissue that indicate the
position of complete degeneration. In
some instances it is with difficulty that
part of the muscle can be distinguished
from adjacent fat.

Course. As the name indicates, the

nature of the disease is progressive. The

rate of progress will vary in different cases,

and at different periods in the same case.

Usually the disease makes a good degree

of progress in one arm before the second

is attacked; and is usually more severe

on one side of the body than the other,

throughout the course of the disease.

Sometimes it begins almost simultaneously
on the two sides; in such cases its prog-
ress is slower, and is more apt to be ar-
rested at an early date. When there is
weakness of the legs without wasting, it
usually occurs simultaneously with the


1. There may be simply a narrowing

of the muscular fiber without any other
changes. Sometimes the striæ are far-
ther apart than normal. Sooner or later
there is an increase in the interstitial con-
nective tissue. This usually begins by a
hyperplastic growth of connective tissue
between and among the primitive fibers,

which increases gradually, and soon muscular fiber is replaced by an increased and abnormal growth of connective tissue.

(See Fig. II, Frontispiece.) There may appear in the muscular fiber a longitudinal striation, which increases until the muscle has the appearance of a fasciculus of longitudinal connective tissue fibers.

2. Again, there appears within the primitive sheath of the fiber small granules, which take the place of the transverse striæ, flowing together, and increasing in size until they form distinct fatty globules at different points within the sheath of the fiber. In this way the muscular substance is completely degenerated into and replaced by fat. (See Fig. III, Frontispiece.) Occasionally muscular sheaths may be seen which contain a clear, transparent substance, with here and there a transverse stria, and scattered through it a few fatty granules. This transparent substance is probably the result of a process quite different from fatty degeneration; it has been termed "vitreous degeneration."

An entire muscle may be completely destroyed by one or more of the above described processes, while adjacent to it may be muscles which are in no way affected. On the other hand, we may have scattered through a large number of muscles, fibers which are completely degenerated; while in the same fasciculus, and by their side, may be found perfectly. healthy fibers. As the disease more frequently begins in the arms and shoulders,

the muscles in this part of the body will, as a rule, be more wasted than others.

If sections of the nerve are made and


C. P. T., Crossed pyramidal tracts, showing some degeneration of motor fibers; D. P. T., Direct pyramidal tracts, with slight changes; A. C., Anterior cornua, broken and having a granular appearance, with absence of some motor cells; A. N. R., Anterior nerve root fibers degenerated; P. C.,

Posterior columns, healthy; P. R., Posterior root, healthy.

An examination of the spinal cord shows the affected parts to be softer than normal; the white matter may be grey and translucent. If transverse sections are made, properly hardened and stained, and examined under a microscope, morbid changes will be found in the anterior cornua and in the anterior lateral columns. The anterior cornua do not take the stain as readily as they do in a healthy section, or as readily as the posterior cornua of the same section. The central part of the cornua, particu

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examined, there will be found scattered through the section. many degenerated fibers; these will be more numerous in the peripheral branches than in the nerve trunk, and especially those terminal branches which supply the muscles.

If these degenerated fibers are traced upward, they will be found to come only from the anterior spiral roots. In the anterior roots of the cord, the degeneration is even more marked than in the nerve trunk. In the nerve trunk the sensory fibers lying by the side of the motor fibers are not at all affected; but the anterior nerve roots, being made up entirely of motor fibers, are more completely affected.



C. P. T., Crossed pyramidal tracts, markedly degenerated; A. P. T., Anterior pyramidal tracts: A. N. R., Showing absence of nerve root fibers: A. C., Anterior cornua. Absence of many motor nerve cells, broken-down, granular appearance; P. C., Posterior columns, having a healthy appearance; P. R., Posterior root, healthy.

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