Under this name M. Du-chenne refers to a disease long known as a variety of general palsy, but which has only recently become well understood. It consists essentially in a gradually progressive atrophy of the muscles, with fatty degeneration of the fibres; and the paralytic phenomena are ascribable to the organic change in the muscle. The credit of first ascertaining its true nature appears to be due to M. Cruveilhier, who demonstrated the existence of fatty degeneration of the affected tissue. It is distinguished from all other forms of palsy, by the irregular and apparently capricious method in which the muscles are struck with the disease; so that in the vicinity of a round plump muscle, is a cavity consequent upon the atrophy of another, thus giving a quite characteristic aspect to the complaint The only other pathological lesion found, is a wasting or atrophy of the anterior roots of the corresponding spinal nerves, which has been noticed in one or more cases. The spinal marrow is quite sound; and it is uncertain whether the nervous atrophy noticed was a result or c of the affection. A singular fact in relation to the disease is, that the muscles retain their electric contractility, or contract under electric excitement, as long as any of the fibres remain undestroyed. It was generally considered quite incurable; but M. Duchenne has demonstrated that it may at least be arrested in its course by means of faradisation; and has even rendered it probable that the muscle may recover its normal structure, if it shall not have been so far destroyed, before the commencement of treatment, as to give no sign of contraction when electrically excited. At least muscles which have been apparently wasted away almost to nothing recover their healthful size, and their power of action. It is said that the atrophy precedes the fatty degeneration; and it may be sup-d that the shrinking is only in consequence of the absorption of the inter-fibrous matter; but M. Duchenne thinks that new fibres are created; and, if so, there is no reason why the muscle might not grow after partial destruction from fatty degeneration, as well as from any other cause. The treatment of the affection generally requires an apparatus of great force and rapid intermissions; and a feeble instrument may fail altogether. Each application, however, should not continue longer than eight or ten minutes, for fear of exhausting the muscle, and thus hastening its destruction. The sensibility of the muscles, which is at first blunted, in general rapidly increases, and it is necessary gradually to diminish the energy of the treatment; but it should be sustained at the highest point possible.

A similar affection is sometimes met with in infancy, and may be treated in the same way.