The attachments, course, and inter-relationships of m. longitudinalis inferior of the tongue in the 15-week human fetus are described. These data are compared with those reported in the literature for the adult structure. In general, the qualitative disposition of lingual musculature is quite complete by this point in development. The division of the muscle mass, by a central decussation, into an anterior and posterior segment was consistently observed in the specimens studied.
Barnwell, Y., et al. (1978). The anatomy of the intrinsic musculature of the tongue in the early human fetus: Part II. Longitudinalis Inferior, International Journal of Oral Myology, 4 (4), 5-8.