In which the atrophy is unusual in distribution, and especially when it is on the distal side of the affected joint, must be regarded with some suspicion, because inflammation may have spread from the joint to a nerve, and distant wasting may have been thus produced. It is said that there is sometimes, at the onset, a considerable weakening of the muscle, interfering with movement more than can be accounted for by the pain in the joint which movement causes, and that such initial palsy is transient (Valtat, Duchenne). But the pain, by its inhibitory influence, usually obscures such palsy, which is indeed confessedly rare.

The atrophy, on the other hand, may be regarded as almost constant. If the onset of the joint affection is acute, the wasting occurs rapidly; in a week or ten days, a difference in the circumference of the limb may be detected by measurement. However long the affected muscle may be, the wasting involves the whole length of it, and not merely the part in the neighbourhood of the diseased joint. The degree varies; usually moderate, and sometimes slight, it is occasionally considerable, so that the femur may be readily felt when the quadriceps femoris is the seat of the wasting, or the head of the humerus may be distinct, and the acromion prominent, if the deltoid is affected. Although the whole length of the affected muscle is always involved, if the muscle is a wide and compound one, some parts may suffer chiefly. Thus in the thigh all parts of the extensor may waste equally, or the rectus or vastus internus may suffer more than the other parts. The wasting increases during two or three weeks, then becomes stationary, but continues as long as the joint disease lasts. When the joint has recovered, the muscles in most cases slowly regain their normal size. Occasionally, especially when the arthritis has lasted a long time, the wasting may continue for months or years after the joint disease is at an end.

The electrical irritability of the atrophied muscles may be normal, but is often slightly lowered, equally to faradism and voltaism. The change is trifling, to be recognised only by comparison with the other side. There is generally a distinct, and sometimes a considerable, local increase in myotatic irritability; the knee-jerk is excessive if the thigh muscles are affected, and a rectus-clonus can sometimes be obtained. A foot-clonus may be elicited when the ankle-joint is affected. Occasionally the increased irritability extends beyond the region of atrophy, so that, for instance, a foot-clonus may be obtained when the knee-joint and thigh muscles are affected, although there is Lo wasting below the knee. As an example of this, which illustrates also the occasional persistence of the atrophy, may be mentioned the case of a young man who jumped over a hoarding and twisted his left leg in doing so. He felt immediately severe pain in the knee, the joint quickly swelled, and became the seat of an acute inflammation which lasted for several weeks, and then slowly subsided. During the inflammation, the thigh wasted. I saw him two years after the onset,

and there was still considerable wasting, involving the whole of the extensor of the knee. The minimum circumference of the left thigh above the knee was three quarters of an inch less than that of the right, although there was no difference between the two legs below the knee. There was a slight diminution in faradic and voltaic irritability in the affected muscles. The knee-jerk was much more considerable on the left than on the right side, and there was a well-marked footclonus in the left leg, but none in the right. A year and a half later the symptoms were unchanged. Very rarely some contracture occurs in the opponents of the atrophied muscles. Sensory symptoms are as a rule absent, but there may be slight tingling in the skin during the acute stage; it is said that areas of anesthesia sometimes develop, but probably in such cases, inflammation has extended to a nerve in the vicinity of the joint.

PATHOLOGY.-Few facts have been ascertained regarding the condition in man. In one case, carefully investigated, the only change was in the muscles, and consisted merely in a narrowing of the fibres, one half of which were below the normal average, while no less than 84 per cent. fell short of a standard which, in health, only 21 per cent. failed to reach. A few presented longitudinal striation (as in Fig. 140), and some of normal width were unduly tortuous; otherwise their aspect was normal. The sheath nuclei were proliferated in places, and, apart from this change, the intermediate substance presented local increase in quantity, especially where the fibres were narrower than normal. This observation agrees with those that have been made on animals, in which the condition has been produced, and in them, moreover, the motor nerves have been found normal (Valtat).† Indications of inflammation have been found in the joint-nerves,‡ as might, indeed, be expected, whatever the mechanism of the atrophy. Visible changes in the spinal cord have never been discovered, but this does not exclude nutritional changes.

We may, therefore, exclude from the possible causes all forms of motor neuritis, both simultaneous, due to the cause of the joint inflammation, and consecutive, communicated to the adjacent nerve from the joint. The latter (a secondary extension of inflammation to the nerve) would manifestly not explain the affection of the whole of a muscle on the proximal side of the affected joint-as, for instance, atrophy of the whole extensor in arthritis of the knee,— although the extension does occur and must be recognised as an occasional event. § We must also recognise the possibility of a simultaneous neuritis, with acute changes in the nerve-fibres, manifested by the reaction of degeneration in the muscles. The event is, how

+ Valtat, De l'Atrophie Musc., &c.,' Paris, 1877. See also Deroche, 'Etude clin. et exp.,' Paris, 1890. See Duplay and Cazin, Arch. Gén.,' January, 1891. § E. g. to the ulnar, in rheumatoid arthritis of the hand (Bury, Med. Chron.,' 1888, p. 182). See on this subject A. E. Garrod, Med.-Chir. Trans.,' lxxi, 265; also Pitres and Vaillard, Rev. de Méd.,' 1887, No. 6.

ever, exceptional. It is certainly separable and to be separated from the common arthritic atrophy; but it is not easy to keep apart the two varieties of neuritis-the simultaneous and the consecutivewhen a case is seen only long after the onset, because a neuritis that arises by extension may travel along the nerve and present an ultimate distribution quite different from that which it possessed at the onset.

For ordinary arthritic atrophies we must seek some other explanation. The nature of their cause long ago suggested to Paget a "reflex influence" on the muscles as the probable mechanism, and Vulpian and Charcot have suggested a similar hypothesis, assuming a derange ment of the nutrition and influence of the motor cells of the cord, to be determined by the morbid impulses from the joint-nerves, and to determine the alterations in the muscles. The theory receives impor. tant support from the fact that the wasting of the muscles is prevented by previous division of the posterior spinal roots (Raymond), which amounts, indeed, to an indirect demonstration of the fact that a reflex process underlies the phenomena. It is doubtful whether we can go much further than this. By preceding hemisection of the cord, it is increased on the side of the operation; but the conditions are here more complex, and the demonstration of the reflex relation less simple, than in the result of division of the roots.

The increased knee-jerk, &c., that attend the wasting, and the curious fact that arthritis may set up a degeneration of the spinal cord, apparently beginning in the termination of the pyramidal fibres (see p. 443), should be kept in mind. They are certainly significant, and suggest that the influence from the joint-nerves acts on the " trolling structure" of the muscle-reflex centre (see p. 201), but more facts are needed before a valid hypothesis can be framed.

con

DIAGNOSIS. The moderate degree of the wasting, with corresponding change in electrical reactions, coupled with the wide extent of the alteration, embracing the whole of the muscles involved, constitute a distinctive characteristic-distinctive, at least, when taken in connection with the preceding joint affection which is the cause of the atrophy. A primary neuritis, causing secondary arthritic adhesions, has its own features-their wider range, so far as function is concerned, and especially their limitation to nerve distribution. Hardly any other malady is likely to be confused with it, except some graver disease, while still in an early stage, but such an affection can only be distinguished by waiting until the nature of the malady has had time to show itself.

PROGNOSIS.-When the inflammation of the joint is brief in duration, recovery of the muscles may be anticipated with confidence. In children, even after prolonged joint disease, the muscles usually regain their normal bulk. In adults the wasting often lasts for a long time after the joint is well, and a cautious prognosis should be given. if the arthritis has lasted long. Even if slight wasting is persistent, Raymond, Rev. de Méd.,' 1890, 374.

normal power is usually recovered, but, as the case mentioned above shows, the symptoms sometimes continue for years. The prognosis should be especially cautious where there is a marked increase in myotatic irritability, or if the atrophy shows a disposition to involve other muscles of the limb than those concerned in moving the affected joint.

TREATMENT. The chief treatment is local; electrical stimulation of the muscles, and gentle rubbing. It is doubtful whether drugs have any influence on the condition, but small doses of strychnia may be given, or added to whatever agent is given for the joint affection. As long as the joint is inflamed, treatment rarely causes any increase in the bulk of the muscle. It is of great importance to secure the early recovery of the joint, and to avoid all influences that cause pain in it, since, as we have seen, it is apparently through the sensory nerves that the joint affection exerts its injurious influence. When the arthritis has ended, the muscles usually recover slowly without assistance, but it is probable that the local treatment accelerates the process. The form of electricity is of little consequence; either faradism or voltaism may be employed, but should only be used in sufficient strength to cause gentle contraction. The muscles act readily to faradism, and a mild faradic current is, as a rule, the best to employ. All painful stimulation of the sensory nerves should be avoided.

MUSCULAR ATROPHY FROM OVER-USE.

Muscles that are much used sometimes waste. The effect is seen most frequently in the small muscles of the hand, especially in persons of weakly constitution, who use these muscles unduly. Thus a young lady devoted many hours a day to "illuminating," during several years, and then some muscles of the thenar eminence began to waste, and became considerably atrophied. Such wasting is scarcely ever met with in the larger muscles, but has been observed in the biceps, consecutive to hypertrophy, in Sheffield smiths (Frank-Smith). The electric irritability is gradually lowered in this local wasting, equally to both currents, as it is in progressive muscular atrophy. We do not know whether this wasting from over-use is purely local, or whether the related ganglion-cells of the spinal cord fail first, and the muscular wasting is secondary to their atrophy. As Gull said many years ago, "it is as reasonable to infer a lesion of the grey matter from overwork as of the muscles." The wasting often persists when the over-use of the muscles is discontinued. Hypertrophy from over-use does not usually give place to atrophy. These two facts are somewhat in favour of the view that the lesion is primarily of the nerve-cells. The wasting in these cases

Guy's Hosp. Reports,' 1862, p. 240.

shows no tendency to extension beyond its original limits. The treatment is, first, the cessation from the excessive exertion of the muscles; secondly, the improvement of the general health, and the administration of nerve tonics, especially of strychnine; and thirdly, the gentle electrical stimulation of the muscles by either faradism or voltaism.

IDIOPATHIC MUSCULAR ATROPHY

(MYOPATHIC ATROPHY; MUSCULAR DYSTROPHY).

Idiopathic atrophy, which is primarily muscular, although it is not one of the diseases of the nervous system, is commonly described with them, because it frequently presents so close a resemblance to the spinal atrophy just described as to be distinguished with some difficulty. Moreover, even the varieties that do not present this close resemblance were for a time, and indeed until lately, believed to be of central nature, to depend on the spinal cord, and to be rightly included among its diseases. Hence the custom of thus describing them has become established, and has now to be followed, although we know that it is based on a mistaken theory. At the same time, not only has the method the advantage of convenience, but it has also some measure of scientific justification. The muscles are more closely allied to the nerves than to any other structures, as regards both physiological properties and pathological susceptibility, and it is doubtful whether any other association would better befit these diseases.

The idiopathic myopathies have received a great amount of attention during the last seven years, and more facts have been ascertained than can yet be used. The difference of opinion regarding the relation of the several forms is still considerable. For the present, it seems better, therefore, to leave unchanged the method of describing them which was first adopted, and which is not without its advantages. Before long, it may be possible to recast the description of these diseases on lines of greater accuracy.* The following account of them may, however, be more intelligible to the reader if it is preceded by a brief sketch of their general pathology. Any points of interest in connection with their history, &c., are left to be mentioned when the varieties are described.

All the diseases of this class seem to depend on a defective tendency of development of the germinal tissue which forms muscles; they are

A treatise upon them by Erb, who made a special study of the subject, is now in course of publication, and cannot fail to make our knowledge far more precise