chap, xxiii.] MOUTH, PHARYNX, AND TONGUE. 191 



with a delicate mucous membrane, identical in struc- 

 ture with that lining the rest of the oral cavity, 

 whereas the upper part is covered with a mem- 

 brane, of which the mucosa projects over the free 

 surface as exceedingly numerous fine and short hair- 

 like processes, the papillae filif or mes, or as less nume- 

 rous isolated somewhat longer and broader mushroom- 

 shaped papillae fungiformes. The papillae, as well as 

 the pits between them, are covered with stratified 

 pavement epithelium. Each has numbers of minute 

 secondary papillae. Their substance, like the mucous 

 membrane of the tongue, is made up of fibrous 

 connective tissue. This is firmly and intimately 

 connected with the fibrous tissue forming the septa 

 between the muscular bundles of the deeper tissue. 

 The mucous membrane is on the whole thin. It 

 contains large vascular trunks, amongst which the 

 plexus of veins is very conspicuous. On the surface 

 of the mucosa is a rich network of capillary blood- 

 vessels, extending as complex loops into the papillae. 

 Lymphatics form rich plexuses in the mucosa and 

 in the deep muscular tissue. Fat tissue is common 

 between the muscular bundles, especially at the back 

 of the tongue. 



259. There are two varieties of glands present 

 in the tongue, the mucous and serous. The latter 

 occur only at the back, and in the immediate 

 neighbourhood of the taste organs ; the mucous 

 glands are chiefly present at the back ; but in 

 the human tongue there are small mucous glands 

 (glands of Nuhn) in the tip. All the glands at 

 the back are embedded between the bundles of 

 striped muscular tissue, and thus the movements 

 of the tongue have the effect of squeezing out the 

 secretion of the glands. Near and about the glands 

 numerous nerve bundles are found connected with 

 minute ganglia. 



