A Critical Review: Primary Diseases of Voluntary Muscles.

THE voluntary muscular system forms in an average male about 43 per cent. of the total body weight. It is a very uniform system and is composed of aggregations of individual muscle fibres each of which are complex multinucleated cells, consisting of a sarcolemmal sheath and its nuclei, a motor end plate, and contractile substance. This system is affected by a large group of primary diseases, i.e. diseases in which the essential disturbance of function is most probably located in the muscle fibre or myoneural junction. The pathogenesis of all these diseases, which have been clearly recognized clinically for half a century, has so far remained obscure. In recent years, however, advances in the physiology of the muscle fibre, especially as regards the chemistry of muscular contraction and the transmission of normal excitation from nerve to muscle, have opened up new methods of approach to the study of muscular diseases and much work along these lines has already been done. The results so far are perhaps infinitesimal compared with the vastness of the problems awaiting solution, but it is to be hoped that they are only the first fruits of greater advances in the immediate future. The time now appears opportune to survey the work in this field, to evaluate the studies which have so far been published, and to discuss the lines along which further progress is likely to be made. It would not be possible in the compass of a short review to deal in detail with all aspects of primary diseases of voluntary muscle. Attention must therefore be specially directed to the results of recent biochemical studies and only such clinical, therapeutic, or histological details included as are necessary to make the review comprehensible. It will also be necessary to exclude from consideration the large group of inflammatory diseases included under the term " myositis " and also such muscular abnormalities as cramp, myokimia, and the weakness in Addison's disease.