Abstract
Cell diameter, cell number and deoxyribonucleic acid (DNA) content were determined in M. pectoralis profundus and M. sartorius of White Leghorn and New Hampshire at 0, 2, 4, 6, 8 and 10 weeks of age. The results were as follows:
1. The cell diameter of the pectoral muscle was almost one-half of that of the sartorius muscle at hatching. However, the cell diameter of the former muscle increased markedly during the first 2 weeks after hatching and became somewhat larger than that of the latter at 2 weeks of age, after which age the cell diameter of both muscles increased at a similar rate.
2. The cell number of the sartorius muscle did not increase after hatching, while the pectoral muscle showed a tendency to increase in cell number during the first 4 or 6 weeks of life.
3. The content of DNA increased 47- to 70-fold and 14- to 15-fold from hatching to 10 weeks of age in the pectoral and sartorius muskles respectively. It is evident, therefore, that nuclear division takes place in the skeletal muscle of the growing chicks.
