On the cross sectional area of skeletal muscle fibres of the rat.

Serial cryostat sections of M. gracilis (pars caudalis) were stained to demonstrate succinic dehydrogenase activity and then used to study the cross sectional area along the length of each category of muscle fibre. The results indicated that the mean area showed no appreciable variation. This finding support the evidence that the cross sectional area is the same along the course of a muscle fibre. Some sources of variation were also discussed.