Muscle spindles in the human anterior digastric muscle.

The occurrence of muscle spindles in the anterior digastric muscle in man was investigated and the fibre calibre spectrum of the corresponding nerve was determined. After removal at autopsy from five individuals of both sexes (aged 23--73), the muscles were stained with Weigert's iron hematoxylin-van Gieson stain and the nerves according to the Alzheimer - Mann - Häggqvist method. Altogether 12 spindles were found in five out of ten muscles. Only muscles from one individual were devoid of spindles. This sparsity or absence was supported by analyses of fibre calibre spectra. The small number of spindles and the fact that they do not occur in all muscles or in all individuals, suggest that they are not an essential source of sensory information.