During unrestricted growth of the pectoral muscle of chickens, the mean cross-sectional area of the fibres increased in proporiton to the total number of nuclei and in proportion to the two thirds power of the weight of the muscle. Continuous restricted feeding from 0 day, which limited the weight of the muscle at 16 days to 44% or 69% of that of chickens fed ad libitum, did not affect these relationships.
A sudden restriction of feed from eight days of age retarded growth of the muscle to approximately 70% of the weight of the controls at 16 days. It did not affect the relationship between the number of nuclei and the fibre cross-sectional area, both of which were also limited to about 70% of those of the controls; but it did disrupt the relationship of these two variates to the weight of the muscle. Subsequent ad libitum feeding caused compensatory growth and restored the relationship.
Starvation or severe undernutrition for a few days, which reduced weight of the muscle and the fibre cross-sectional area by approximately 25%, caused no loss of nuclei, thereby disrupting both relationships. Subsequent ad libitum feeding initially caused an increase of muscle weight and fibre cross-sectional area but no increase in the number of nuclei. This restored the relationships, which were then maintained during subsequent compensatory growth.