MUSCULAR ATROPHIES It has been known since about the third decade of the last century that there occur in aclults and children diseases consisting in atrophy or increase in volume of the muscles, with paralysis of a progressive character. Gradually, through the investigations of Aran, Duchemie, Erb, Schultze, Leyden, Moebius, Charcot, J. Hoffman and many others, a number of different forms of these muscular atrophies were distin guished, and this led to the erection of different types and incidentally to the subdivision of all the progressive nmscular atrophies into a number of subgroups. The basis for this detailed classification was found in the clinical course, the age when the disease makes its appear ance, the tendency to occur in members of the same family and, es pecially, in the pathology. On pathologic grounds the division was niade into spinal and myogenous, according as the motor eells of the spinal cord or the peripheral muscular system were found to exhibit, pathologic changes. It was also found that the spinal form as a rule attacks adults and does not tend to °Ceti'. in members of the same family, whereas the myogenous variety preferably occurs in children and exhibits a family tendency. Thus, the different kinds of muscular atrophy appeared to be, sharply differentiated, but before long this sharp division had to be abandoned. On the one hand, 1Verdnig and Hoffmann described a pronounced spinal and familial disease of the muscles in earliest childhood; on the other hand, isolated cases were observed presenting signs of both forms of the disease, and occasionally pathologic changes in the spinal cord were found in apparently myo genous forms of muscular atrophy. Thus the sharp line of distinction
between spinal and myogenous atrophy became somewhat blurred, and with regard to the individual waffles of myogenous muscular atrophy the finding of certain constantly recurring complexes had led to the classification of certain definite and distinctive types. But, as in the case of the forms of diseases occurring in families which we have described above, more and more "impure cases" and "transitional forms" Were observed, making it impossible to retain the classification into the usual types. Erb deserves the credit of having spoken the decisive word on this question by grouping all myogenous diseases under the general head of nmscular dystrophy, and at present most authorities have accepted this standpoint.. Hoffmann's neural (neurotic) atrophy represents an apparent transitional form between spinal and muscular paralysis of nmscles. With this reservation we shall in the following discussion retain the customary classification of muscular atrophies, as it will best enable us to sift the large amount of available material.