466 MANUAL OF HISTOLOGY. 



potash or soda. According to Ordenstein, the sugar-forming ferments 

 appear in the corresponding fluid obtained from the dog (Bidder and 

 Schmidt, Bernard). 



247. 



The tongue is an organ essentially muscular, but covered by a mucous 

 membrane which, over the greater portion of the anterior part of the 

 dorsum, is studded with a multitude of highly developed papillae supplied 

 with nerves, the gustatory pqpillce, which constitute the whole an organ 

 of sense. 



Leaving the greater portion of the description of its striped fibres, 

 which have a partly perpendicular, partly longitudinal, and partly oblique 

 direction, to general anatomy, we shall merely touch here on one or two 

 points of special interest. 



That portion of the tongue known as its fibro-cartilage, which occupies 

 the middle line of the organ in the form of a thin vertical septum, cannot 

 be numbered among the cartilaginous structures, seeing it merely consists 

 of densely interwoven bundles of connective-tissue. At either side of this 

 band the two genioglossi pass up into the substance of the tongue, inter- 

 mixed, as their fibres diverge, with the fibres of the transversus linguae, 

 which cross the former more or less at right angles. The greater part of 

 the substance of the organ is formed by these two muscles. The hyoglossus, 

 with its two portions, the first of the muscles entering into the formation 

 of the border of the tongue, passes to tne lateral portion of the organ in 

 manner similar to the genioglossus, and likewise crossed by the external 

 fibres of the transversus on each side. The styloglossus sends its weaker 

 internal division between the genioglossus and hyoglossus and as far as 

 the fibro-cartilage. Its longer external band passes forwards on the 

 external surface of the hyoglossus, intermixing behind the frsenum and 

 anterior to the foremost extremity of the sublingual gland, with the fibres 

 of its fellow of the opposite side. Besides these there are longitudinal 

 bundles of muscular fibres coursing from the root to the tip of the tongue, 

 partly on the dorsum and in part near its inferior surface. The latter are 

 the most numerous, and go by the name of the lingualis muscle. They 

 are strengthened anteriorly by fibres from the external division of the 

 styloglossus. Their course is between the genio- and hyoglossus muscles 

 towards the tip of the tongue, where their fibres diverge, some passing 

 upwards and others still forwards. The superficial layer of bundles 

 (lingualis superior) is spread out over the whole dorsum of the organ 

 under the mucous membrane. Those muscle bundles which are lost in 

 the mucous membrane, such as the ascending fibres of the genioglossus 

 in the middle line, and of the hyoglossus in the lateral portions of the 

 organ, may be seen to bifurcate at acute angles, and terminate in the 

 connective-tissue in conical points. 



The most important part, however, of the tongue is the mucous mem- 

 brane itself. This is covered over with the flattened epithelium of the 

 mouth ( 90), and is, with the exception of having papillae, in no essential 

 feature different from other mucous membranes. Its connective-tissue 

 substratum is tolerably strong, and interspersed with numerous elastic 

 fibres. It is also extremely vascular. 



In the gustatory portions there is no submucous tissue, its place being 

 taken by a closely woven layer of fibrous tissue, the undermost portion of 

 the substance of the mucous membrane. 



