1134 



TONGUE. 



taining some fat, particularly at its inferior 

 part and the median fibrous lamina, when the in- 

 termuscular areolar tissue is sufficiently dense 

 to deserve that name ; anteriorly, with the frse- 

 nurn, to which it is subjacent; inferiorly, with 

 the geniohyoid; and externally, with the sub- 

 lingual gland, the mylohyoid, hyoglossus, and 

 inferior lingualis muscles, the ranine artery, and 

 the gustatory nerve. The hypoglossal nerve 

 threads its fibres, and passes forwards among 

 them. Action: To raise and draw forwards 

 the tongue ; to assist in constricting the 

 pharynx ; to protrude, retract, or depress the 

 tongue in the mouth, according as all or part 

 of the fibres are employed ; to depress the 

 centre of the tongue, and render it concave, 

 from side to side. 



c. Accessory extrinsic muscles. These 

 are, in short, all the muscles that move 

 the os hyoides without being attached to 

 the tongue, for whatever, moves the hyoid 

 bone must move the tongue, which is fixed to 

 it. They are accessory to the proper extrinsic 

 muscles in two ways, either by acting in con- 

 cert with them, or by facilitating their action 

 on the tongue by rendering the hyoid bone a 

 fixed point. Thus, in the first method, the 

 stylohyoid and posterior belly of the digas- 

 tricus concur with the styloglossus in draw- 

 ing the tongue upwards and backwards. In 

 the same way, the anterior belly of the digas- 

 tricus, the mylohyoid, and geniohyoid, con- 

 cur with the inferior portion of the genio- 

 glossus in raising and drawing forwards the 

 hyoid bone, and facilitating the protrusion of 

 the tongue from the mouth. By the second 

 method the muscles from the styloid process 

 to the hyoid bone assist the longitudinal in- 

 trinsic muscles of the tongue by rendering the 

 base a fixed point from which they can ad- 

 vantageously act on its length, and in the 

 same way the inferior set of hyoidean muscles 

 are accessory to the hyoglossus by fixing 

 the hyoid bone down. More might be said 

 on this subject, but enough has been stated 

 to indicate the important relation of these 

 muscles to the proper muscles of the tongue, 

 and for the sake of brevity that may suffice. 



Movements of the tongue. All the infinite 

 variety of movements by which the tongue is, 

 by virtue of its complex muscular organisa- 

 tion, susceptible, may be arranged under 

 two heads, its extrinsic and intrinsic move- 

 ments ; sometimes dissociated, more fre- 

 quently concurrent : for the sake of clearness 

 I shall consider them separately, and then 

 group them. 



First, the intrinsic movements of the tongue 

 are of two sorts ; those affecting its length, 

 and those affecting its direction. 



a. As affecting its length. The elongation 

 of the tongue is provided for, like all in- 

 trinsic elongation, by diminution of calibre ; 

 in the tongue this is produced by transverse and 

 vertical contraction, especially the transverse, 

 whereby the tongue becomes at once elon- 

 gated and pointed ; by this means the tip of 

 the tongue can be protruded beyond the teeth 

 without any movement of the organ en masse, 



or any assistance of the extrinsic muscles. 

 From this elongated state it is restored to its 

 original position and shape by the contraction 

 of all the longitudinal fibres composing the 

 cortical portion, which draw it directly back, 

 the transverse and vertical fibres at the same 

 time ceasing to act. Thus we see that the 

 central and cortical portions of the intrinsic 

 muscles are antagonistic ; but they are capable 

 of association : for instance, when the tongue 

 is to be flattened and its sides pressed against 

 the teeth without any elongation, an action 

 very frequent in mastication and in the pro- 

 nunciation of some letters, this is done by 

 the contraction of the vertical fibres associ- 

 ated with the longitudinal, the one diminishing 

 the vertical thickness, and so spreading the 

 tongue out, the other preventing the elonga- 

 tion which the diminution of vertical thick- 

 ness would otherwise be attended with. 



b. As affecting its direction. The direction 

 of the tongue is entirely regulated, as far as 

 the intrinsic muscles go, by the longitudinal 

 fibres, and their power of modifying the direc- 

 tion of the tongue, as well as 'shortening it, 

 depends on their power of partial action : 

 thus the lateral lingual of one side can act, 

 or of the other ; the superior or the inferior, 

 and the point of the tongue is of course moved 

 to the side of the acting muscle. This modi- 

 fication of the direction of the tongue is, per- 

 haps, the most complete movement that it 

 possesses; it is certainly the most extensive : 

 by it the tip of the tongue may be depressed 

 deep below the incisor teeth, or reflected back 

 on the soft palate, so as nearly to touch the 

 uvula; or laterally, from the pillars of the 

 fauces on one side it may be carried round 

 the cheeks and alveolar arches to the same 

 position on the other side: these are the 

 cardinal points, up and down, right and left; 

 they may be united in any proportions, so as 

 to carry the extremity of the tongue to any 

 intermediate position. 



Moreover, the movements affecting the 

 length of the tongue may concur with those 

 affecting its direction ; for instance, on apply- 

 ing the tip of the tongue to the root of a 

 canine tooth of the upper jaw, on the outer 

 surface of the alveolus, the tongue is elon- 

 gated, and vertico-laterally flexed; on apply- 

 ing it to the last molar tooth of the lower jaw 

 it is laterally flexed and shortened. 



Secondly, the extrinsic movements of the 

 tongue admit of the same division as the 

 intrinsic, into those regulating its length, and 

 those regulating its direction or shape. 



a. Thus the tongue is carried upwards and 

 backwards by the styloglossus, assisted by 

 the other styloid muscles, downwards and 

 backwards by the hyoglossus, directly back- 

 wards when these both concur; and it is 

 carried forwards and protruded from the 

 mouth by the genioglossus. These move- 

 ments, en masse, almost always concur with 

 the intrinsic movements, the whole organ 

 following to a certain extent the direction 

 of the extremity. 



b. But the extrinsic muscles affect very 



