Abstract
The gl. sublingualis and the gl. submandibularis in a human embryo of 3 or 4 months are found as simple branched duct systems sporadically arranged in the loose connective tissue, and their alveoli are formed by undifferentiated gland cells arranged in one row. In the gl. sublingualis, however, some mucosal cells are already formed. The large ducts of these glands are lined by a double-rowd cubic or cylindrical epithelium, but the intercalated and the secretory ducts of the submandibular gland are not yet differentiated and are lined by a single-rowed cubic epithelium. These glands are abundantly provided with blood vessels and nerves.
The ganglion submandibulare is extremely well developed and stretching toward the sublingual gland, forms the so-called ganglion sublinguale. Small ganglia are also found migrated into many places in the n. lingualis. More or less thick nerve bundles are found running out of these ganglia into the submandibular and the sublingual glands, and small ganglia are frequently found in these bundles too.
The nerve cells in the ganglia are already in a considerably high development. They are in the form of multipolar cells with 3-5 nerve processes and contain each one or sometimes two large nuclei, which are usually eccentric or marginal-standing and show as yet no formation of nucleoli within them. Fine nerve fibrillar nets are contained in the cell bodies.
The short processes from the nerve cells are not yet in the stage of ramification, but running only a short course, and in sharp points. One or sometimes two long nerve processes are sent out per cell. The accessory cell plasmodium (STÖHR) is as yet very poorly developed, being provided with one or two cell nuclei around a nerve cell. These nuclei are presumed to increse in number with the differentiation of the short processes. The connective tissue capsule covering such a plasmodium is also still very poorly developed.
The nerve bundles running in the ganglia submandibulare and sublinguale are already very conspicuously formed. These always consist of fine vegetative fibres, which show mutual nervous anastomosis here and there. The bundles contain chromatin-poor club-shaped SCHWANN's nuclei rather frequently.
The external vegetative fibres coming into the ganglia also undergo frequent anastomosis and gradually losing in size, develop finally into the pericellular terminal reticulum common to a number of nerve cells. This reticulum is formed of fine nerve fibrils showing frequent change in size and forming an irregular mesh-work. No direct connection seems to exist between the reticulum and the nerve cells.
The fibres in the numerous bundles running into the two glands comprise both sympathetic and parasympathetic fibres, but it is impossible to distinguish between the two kinds. The development of the vegetative periarterial plexus formed around the arteries is already much advanced. This plexus here and there anastomosis with the vegetative nerve bundles mentioned above.
The termination of the vegetative fibres distributed in the salivary glands is also represented by the STÖHR's terminal reticulum formed of finest fibrills and extending cordwise. The mesh-work of the reticulum in the glands is finer and more regular than that of the pericellular terminal reticulum above. SCHWANN's nuclei are frequently found in this reticulum too. The terminal reticulum is in particularly good formation around the alveoli and the ducts of the glands and diffuses closely in contact of the epithelial cells, but apparently never send out side branches into their cell bodies. The terminal reticulum stands in tactile control over the smooth muscle fibres in the arterial walls, and is frequently found in the mucous membrane of the bottom of the oral cavity too.
The sensory fibres originating in the n. lingualis, though as yet unprovided with myelin sheaths, are much thicker than the vegetative fibres.
