THE MOUTH AND TONGUE. 379 



duct, situated near a larger duct, discharge into the latter near 

 the surface of the mucous membrane, appearing like a small 

 accessory glandule. The walls of the glandules consist of a 

 structureless basement-membrane, upon the interior surface of 

 which are superimposed cylindrical, clear, almost homogene- 

 ous-looking cells, with oblong nuclei. 



As for the connection of the buccal mucous membrane with 

 the underlying structures, different conditions obtain in differ- 

 ent regions. Its connection with the hard palate and gums 

 has been described above. Where it is superimposed upon a 

 sharply defined muscle, e.g., over the floor of the mouth, and 

 over the sublingual gland, it passes into the connective- tissue 

 sheath of the part. 



The blood-vessels of the mucous membrane are arranged in 

 two systems of superficially extended networks. The deeper 

 one, located in the submucosa, is composed of the mutually 

 anastomosing branches of the afferent and efferent vessels. 

 From this network many smaller vessels penetrate into the 

 tunica propria, which, by division into still smaller branches, 

 and by frequent anastomoses with one another, form the more 

 superficial and finer-meshed vascular net. In both nets the 

 venous and arterial branches run tolerably parallel. From the 

 superficial network very fine branches enter the papillae, where, 

 according to their size, they form either capillary nets or sim- 

 ple loops. 



The lymphatics form wide networks in the submucosa, 

 and narrow nets in the tunica propria. Single small vessels 

 cross those of the vascular nets. That lymphatics pene- 

 trate the papillee is doubtful. The nerves of the buccal mu- 

 cous membrane form in the submucosa more or less dense 

 plexuses, in which many separations of the single nerve-fibrils 

 may be noticed. Thence numerous filaments, partly isolated, 

 partly arranged in small bundles, and always medullated, 

 ramify, and radiate in wider ramifications toward the super- 

 ficial layers of the mucous membrane. A certain number 

 of nerve-fibrils approach the papillae, to implant themselves 

 either at their bases or at the centre of their apices, some- 

 times even at their extremities, in the terminal bulbs of 

 Krause. Such fibrils are most abundant in the lips and in the 

 anterior surface of the velum palati, and in smaller quantity in 

 the cheek and bottom of the mouth. Nerve-fibrils may some- 



