Spatial distribution of muscle fibers

The analysis of Gates and Betz (1993 Anat. Rec., 236:381-389) of the spatial distribution of two different populations of muscle fibers in the lumbrical muscle of the rat is discussed. The conclusion that muscle fibers belonging to a single motor unit are distributed at random in most muscles appears to need reconsideration. A new technique is applied to some examples to show that the amount of clustering of fiber types in a muscle cross section can be quantified.