Morphological and morphometric studies of the skeletal muscles of rachitic rats.

The question of "myopathia rachitica" was pursued in a disease progress study using rachitic rats. The length of the study was 18 weeks. During this time a discrete dystrophic myopathy formed. The morphometric examination showed muscle fibre diameters 8--24 mu less than those of healthy control rats in correlation with the degree of rachitis. The absence of fiber growth in the C fibres was conspicuous. The question of the relation of these findings to the inactivity, osteomalacia and changes in metabolism in rachitis was discussed. The myopathic changes can not be solely interpreted as a result of inactivity, but the cause of myopathia rachitica remains unclear.