singular form of paralysis, in which extreme feebleness of the muscles is combined with an appearance of extraordinary development and vigour, was first studied and described by Duchenne, of Boulogne. Almost at the same time, however, Dr. Edward Meryon, in England, had published some interesting particulars of four boys in the same family who were all affected with what appears to have been hypertrophic paralysis, although the author at the time was of opinion that the disease was identical with progressive muscular atrophy. Many cases have since been placed upon record, and there must be few children's hospitals which have not at one time or another had an example of the disease their walls.
Causation.—Of the etiology of the infirmity nothing is known. It is in the large majority of cases confined to the male sex: In Dr. Meryon's first series of cases, above referred to, all the boys (four) of the family suf fered from it, while the eight girls escaped. This fact also illustrates another tendency of the disease, viz., its proneness to attack several mem bers of a family. Two, four, and more children of the same parents have been known to be affected, and Dr. Meryon has referred to a striking instance in which eight brothers all died of the disease. This tendency seems to point to a hereditary element in the etiology of the infirmity. In investi gating this question it is not enough, as Dr. Gowers has pointed out, to ascertain merely the health of the parents. , Females are rarely affected by it, and males, the subjects of the disease, usually die at or soon after puberty. Therefore the tendency must be searched for amongst the collateral branches of the family. Such evidence is generally found on the side of the mother, and instances of the disease in some members of her family can be discovered sufficiently often to determine positively the fre quent existence of this one-sided inheritance.
The disease appears to be limited to childhood, and, indeed, is often congenital, the first symptoms manifesting themselves during infancy or shortly after that period. It seldom begins after the sixth year.
Morbid Anatomy.—No morbid changes have as yet been discovered in any part of the nervous system to account for the disease, but the changes in the affected muscles themselves are sufficient to explain the phenomena of the affliction, and especially the apparent inconsistency between the unusual size of the muscles and their remarkable want of power.
In the muscles the morbid process consists in an overgrowth of the interstitial connective tissue between the fibres. The nucleated fibrous
tissue and the fat cells gradually increase in quantity and compress the muscular fibres. These under the pressure become narrower, and their shim farther apart, although still distinct; afterwards the striations become indistinct, and the fibres dwindle and eventually disappear, leaving the empty sarcolemma sheath running by the side of the fibrous bundles and proliferated fat cells.
If the fat is greatly increased in quantity, the muscles on section may have the appearance of a fatty tumour in which no sign of muscular red ness is visible to the naked eye. tinder the microscope the fibres are seen to be separated by fat cells, but it is not common to find fatty degeneration of the muscular fibres themselves.
Symptoms.—The earlier symptoms are very apt to escape notice as they have no distinctive character. They consist merely in weakness of certain muscles, usually those of the lower limbs, and sometimes of the back. If the disease begins in early infancy, before the time for walking has arrived, the child is noticed to be heavy to lift, and to want the responsive " spring " which is so marked a feature in the healthy infant. In such a case it is late before he acquires the power of walking. If he has been able to walk before the disease begins, he very quickly gets tired, and shows a curious unsteadiness when on his legs. He can be thrown off his balance by a slight push, and when on the ground rises again with diffi culty. When the weakness of the muscles has reached a certain degree, the child is forced to assume a characteristic attitude. In standing he separates his legs widely, and throws his shoulders backwards so as to exaggerate the antero-posterior curve of the lumbar spine. Consequently his belly is protruded, and, in a marked case, a vertical line dropped from the back of the neck falls clear of the buttocks. This attitude is the con sequence of weakness of the extensors and flexors of the hip and the exten sors of the knee—the muscles which maintain the body upright in stand ing. The child, feeling these to be insecure, tries by separating his feet to enlarge his base, and as, owing to the weakness of the extensors of the hip, the pelvis is inclined unnaturally forwards, he throws his shoulders back wards so as to keep the centre of gravity in the normal position. As he walks he still continues to separate his feet widely, and he sways his body from side to side so as to keep the centre of gravity over the foot upon which the weight of the body is resting.