Topological distribution of muscle spindles in the human tongue and its significance in proprioception.

In order to obtain numerical data concerning the lingual muscle spindle distribution, the muscle spindles were histologically surveyed on the serial frontal and horizontal sections (stained by hematoxylin-eosin) from the apex to the radix of the tongue. On one side four hundred and sixty-six muscle spindles were counted in seven muscles, the superior longitudinal muscle containing 159 spindles, the genioglossus 80, the transverse 79, the styloglossus 75, the hyoglossus 37, the inferior longitudinal 22 and the vertical 14. The chondroglossus and the palatoglossus are devoid of the spindles. The question of whether the proprioceptive impulses from the lingual spindles lie in the hypoglossus nerve or in the lingual nerve has remained unsolved. This histological confirmation of the pathway and primary cell station of the lingual proprioceptive afferents is the subject in which the authors are greatly interested.