Development and peripheral innervation of the palatal muscles.

Following the observation of 51 embryos and human fetuses of between 9 and 190 mm vertex/coccys length, cut transversally, frontally, or sagittally, depending on the case, and coloured with HE, Azan, or by the Bielschowsky method, we studied the development, and peripheral innervation of the palatal muscles. We reached a series of conclusions which we put forward in this paper. The m. tensor veli palatini is the one which develops earliest. It derives from the sam blastematic mass as the muscles of mastication, and it is innervated by a branch of the n. mandibularis. The m. levator veli palatini and m. pharyngopalatinus coincide chronologically with the appearance of the m. cephalopharyngeus. They derive from the pharyngeal musculature, and are innervated by fibres proceeding from the n. glossopharyngeus, in the case of the first one, and, in the case of the second, by direct branches from the n. glossopharyngeus and n. vagus, which penetrate the muscle directly, without prior contact with any nerve plexus. The m. uvulae is first formed, at the time the palatine processes close. In the first place, two outlines may be seen; but after 50 mm approximately it is formed by one muscle only, on the medial line; it is innervated by branches which proceed from the posterior n. palatinus. The m. glossopalatinus is the last to appear. It is closely linked to the musculature of the tongue and, therefore, we think that it derives from the hypobranchial musculature, and that is innervated in the body of the tongue itself, by means of the n. hypoglossus.