Radiographic assessment of calf muscle growth in the rat.

The growth of the calf muscle of the rat has been examined using a non-destructive,, radiological procedure. The growth was followed longitudinally in one set of rats from 3-228 days of age. A second group containing 165 animals was examined cross sectionally. In these animals the weight as well as the width of the muscle was recorded. It was concluded that growth of the calf muscle in width is more complex than the grwoth of the tibia, as a second growth peak was seen between 28 days and 35 days in the muscle but not in the tibia. It was observed that in animals greater than 150g body weight the muscle radiological shadow of the female was greater than that of the male, but this difference was not seen in muscle weight. The relationship between muscle size and muscle weight was not uniform: if the lightest animals were excluded then a logarithmic relation appeared, and if the heaviest animals were excluded, a cube relation was found. Variation in weight was always greater than in width, and it was concluded that muscle width could not be used for accurate estimation of muscle weight.