Abstract
Histopathological studies were carried out on skeletal muscles of 1, 723 individuals consisting of embryos, and abnormal and normal chicks which had been collected on the days of hatching during the same year. Muscle lesions were readily found in 360 (21%) of the specimens at low-power magnification microscopy. Muscle fibers in the lesions showed mainly focal swelling, focal rarefaction with a lack of myofibrils and sarcoplasm, and the appearance of basophilic substance. Some of the lesions were associated with mild reactive changes in the interstitial connective tissue. Based on the findings of rarefied areas in the affected muscle fibers, a pyesumption was made that these muscle lesions might have occurred in immature muscle fibers and be regarded as a hypoplastic change.
