Growth in Muscle

Abstract

IN the growth of the eye muscles of plaice, I have made an observation which may concern the general problem of muscular development. When transverse sections were taken of the head of a young plaice 4 cm. long, its internal rectus was seen to consist of 42 distinct fibres. Similar sections were taken of plaice of lengths increasing up to 10 cm. and it was found that up to 8 cm. the muscle grows in stoutness by the thickening of the fibres—a fibre in the internal rectus of a 8 cm. plaice being twice as thick as the fibre of a 4 cm. fish: the number of the fibres in the muscle showed practically no increase. But a section through a plaice 10 cm. long revealed a sudden proliferation in the number of fibres so that about 342 could now be counted. Here is evidence therefore that the muscle fibres, originally formed from the embryonic cells of the mesoderm, do not keep to a constant number all through life, and that a muscle grows not only by a thickening of the component fibres as happens in the early stages of plaice, but also by a multiplication of them as happens later.