The conclusion that the appearance at once suggested to me was, that the sarcolemma, condensed by the diminution of its contents, passed off from the acuminated extremity as a tendon of white fibrods tissue ; and this opinion was confirmed when I thought of the genesis of these structures. If, as seems probable from the account given by Schwann and other physiologists of the de velopment of muscle, the sarcolemma is the persistent cell-wall of the original for mation-cells of the fibre, and if white fibrous tissue is true zellenfasern — altered cell-wall of cells that have become elongated at their opposite nodes, and plicated as it were, then we reduce the sarcolemma and the white fibrous tissue to the same category — altered cell-wall. The function of the cell wall of the muscle-cell is to secrete that peculiar matter within it which ultimately becomes sarcous matter ; the function of the cell-wall of the fibre-cell is to become elon gated and plicated, or otherwise longitudinally striated. To explain, therefore, the gradual passage of one structure into the other, we have merely to suppose, on the part of the cell wall, the gradual mergence of one function, and taking on of the other. These considera tions at any rate tend to obviate any ante cedent objections to the opinions suggested by the appearances, that would have arisen if there had been any thing essentially heteroge neous in the nature of the structures con cerned. The fact, that Mr. Bowman's obser vations were made on the lower animals — fish, crustacea, and insects — may perhaps account for the difference of the appearances. It is a subject that requires more investiga tion, and no structures seem to me so much adapted for this purpose as the tongues of the lower vertebrate.
b. Extrinsic muscles of the tongue. —These are four in number, the palatoglossus, the stylo glossus, the hyoglossus, and the genioglossus ; at taching the tongue to the soft palate, base of the skull, hyoid bone, and lower jaw, and mov ing it nearly in the four cardinal directions, up wards, downwards, backwards, and forwards. They are all more or less of a mixed nature, being continued in some degree into the tongue. They move the organ en masse, and attach it to distant parts by virtue of their extrinsicportion ; they contribute to the sub stance of the organ, and affect its form, by virtue of their intrinsic portion. It is this continuity of the substance of the tongue with its means of connection to distant parts that makes those connections so strong and safe ; it is, this prolongation of the extrinsic muscles into the tongue that renders the association of the extrinsic and intrinsic movements so intimate.
The palatoglossus (glosso-staphylinus), the smallest of these muscles, constitutes the connection between the soft palate and the sides of the tongue. At its origin in the soft palate its fibres are mingled with those of the palatopharyngeus ; as it descends to the tongue it becomes much narrower, constitut ing the anterior pillar of the fauces ; and arrived at the sides of the tongue, it again spreads out, and its fibres mingle with those of the styloglossus, some of them passing transversely into the medullary structure. It lies immediately beneath the mucous mem brane, and in front of the tonsil. Action : To constrict the fauces (hence its name, con strictor isthnzi fauciunz) by depressing the soft palate and raising the sides of the tongue.
The styloglossza.— A small slender muscle arising by a pointed tendinous origin from the inferior half of the styloid process of the tem poral bone, and also slightly from the stylo maxillary ligament. It passes downwards and inwards to the base of the tongue, opposite to which it expands and becomes flattened; a few of its fibres bend inwards, the majority being continued longitudinally along the side of the tongue, where they may be traced to near the apex, contributing to the formation of the lateral lingual muscle. As they pass forward, they mingle with those fibres of the hyoglossus that have a similar direction, and with the inferior lingual. Relations: Ex ternally, with the parotid and submaxillary glands, the external carotid artery, the facial artery, the Whartonian duct, the lingual branch of the fifth nerve, and the stylomax illary ligament ; internally, with the stylo hyoid ligament, internal carotid, superior constrictor of the pharynx, the jugular vein, and hyoglossus muscle. Action: To retract the tongue, to raise and expand its base, and to render it concave from side to side by rais ing its borders.
The hyoglossus.—Flat, thin, and ascending nearly vertically, this muscle approaches a quadrilateral form ; but, from the dorsum of the tongue ascending as it passes forwards, its anterior border is much larger than its posterior. It arises from the posterior ex tremity, and from the superior border and outer surface of the greater cornua of the os hyoides, and from the body in their immediate neighbourhood. From this double origin the fibres ascend in two distinct sets. Those from the greater cornua, passing up nearly parallel to one another, are inserted into the sides of the tongue ; those from the body expand as they ascend, arch forwards, and, gaining the side of the tongue at a point su perior and anterior to the other, pass forward along the border of the tongue, and unite with the styloglossus to form the lateral lingual. These two portions are separated below by a cellular interval ; and above a few fibres of the styloglossus pass in between them. Al binus has described these as three distinct muscles : one, the cerato-glossus, arising from the greater cornua ; another, the basin glosses, from the body : and a third, intermediate, the chondro-glossus, taking its origin from the lesser cornua. Relations : The external relations of this muscle are, — from above downwards, with the submaxillary gland, the hypoglossal nerve, the mylohyoid, stylo hyoid, and digastric muscles ; internally, it covers the glosso-pharyngeal nerve, the middle constrictor of the pharynx, the lingual ar tery, the stylohyoid ligament, the geniohyo glossus, and, at its attachment to the tongue, the inferior lingualis, which separates it from the last mentioned. Bichat erroneously states that the lingual artery ordinarily passes be tween its two origins. Action : To depress the sides of the tongue and render its dorsum convex ; to retract the tongue and draw it downwards. It is more frequently associated with other muscles than isolated in its action ; and accordingly as it acts alone or together with other muscles, either as concurring with them or antagonising them, so its actions vary.