85 



of the anterior half of the muscle pass upwards, and the greater portion 

 of them likewise forwards. 



I am not now concerned with the so-called genio-pharyngeus, 

 which has been described as an offset from the genio-hyo-glossus, 

 passing from the edge of the tongue to the mylo-hyoid ridge, and 

 constituting the glossal attachment of the superior constrictor of the 

 pharynx. 



If the relative disposition of the inner or opposed surfaces of the 

 genio-hyo-glossi muscles of opposite sides be carefully examined, it 

 will be found that they are not parallel, as usually described in works 

 on anatomy, but disposed, relatively to one another, at an acute angle, 

 salient forwards. 



This angle is maintained, and the intervening space is filled up, by 

 a soft, granular, adipose substance, which exists in greatest quantity 

 behind, in the vicinity of the os hyoides, where the interspace between 

 the muscles is widest. To this substance Haller attributes- the func- 

 tion of lubricating the muscular fibres, and thus obviating the effects of 

 mutual friction ; but this purpose we know to be served by a fine fluid, 

 which during life, and at the temperature of the body, is probably in a 

 state of halitus ; besides, in other muscles and muscular organs, for 

 example the heart, where action is not less vigorous, fat does not exist ' 

 in the healthy state. 



The principal, if not the only purpose of the lingual fat or smegma 

 seems to be, to divarigate the genio-hyo-glossi muscles in conformity 

 with the figure of the tongue, and thereby confer upon that organ 

 greater precision and concentration of force in its forward movements. 

 Haller, in his treatise Be Fabrica et usu Linguce, whilst attributing to 

 this fat the purpose already mentioned, admits that it exists in greatest 

 quantity near the os hyoides, where obviously muscular movement is 

 least active, and where, consequently, the function he assigns to it 

 would be least required: he says — " Interstitia enim hujusmodi fibrarum 

 ad basin linguae, qua, ossi hyoidi adhasret, prsecipue copiosa pinguedine 

 replentur."* 



Malpighi,f whilst admitting that the principal situation of the lin- 

 gual adeps is at the base of the organ, assigns to it no particular use. 



As regards the agency by which the tongue is protruded from the 

 mouth, all anatomists are agreed in regarding the genio-hyo-glossi 

 muscles as the sole active agents in that movement. HallerJ says, 

 " valet hie musculus (viz. genio-glossus) linguam in anteriora trahere, 

 et simul ex ore pro trahere." 



This, it will be perceived, is a very vague and indefinite account of 

 the action of these muscles, and still less satisfactory is it, as will 

 appear in the sequel, as an explanation of the mode in which protru- 

 sion of the tongue is accomplished. Yet, in no work preceding that 

 of Haller, nor in any written since his time that I have had an oppor- 



* Haller " De fabrica et usu Linguae," c. xxxviii. 



f Marcelli Malpighi exercitas epistolica de lingua ad Alphonsum Borellium 1664, 

 p. 38. +" Opus citat.," c. lxriii. 



