Messrs. Hancock and Embleton on the Anatomy w/Eolis. 7 



the under and posterior surface of this band that the muscle [a) 

 we have mentioned, as coming down from the upper part of the 

 buccal mass by the side of the oesophagus, is attached. The use 

 of this inferior band is to pull the posterior end of the ridge of 

 the tongue downwards, and thus assist in the rotatory motion 

 of this organ backwards, by which food is carried to the opening 

 of the (Esophagus. The other, the superior band, PI. I. fig. 5 c, 

 lies within the curve of the former, and has its ends fixed to the 

 ends of the spiny ridge of the tongue, which it will serve to ap- 

 proximate ; but it will more particularly pull downwards and back- 

 wards the anterior end of the tongue, being the main agent in its 

 rotatory motion forwards, on account of the muscles which come 

 down from the upper part along the posterior surface of the buccal 

 mass pulling upon the inferior semicircular band to which they 

 are attached, and thus making the posterior end of the tongue a 

 fixed point. 



Of the three muscles here last mentioned, the posterior a, and 

 the superior c, are associated together in action, and are opposed 

 by the inferior Z>, which is also in part intermediate in situation 

 between the others. Altogether they are the chief instruments 

 in producing the rotatory backward and forward motions of the 

 tongue, whilst the muscles that overlie them laterally assist in 

 the rotation, and regulate the place and degree of curvature of 

 the ridge, whilst they can depress the tongue in totality. Now, 

 the nearly circular space that is left between the concave border 

 of the upper semicircular muscle and the concavity of the ridge 

 of the tongue is filled up by a mass of stout, short, transverse 

 fibres </, which appear to give strength and stability to the lin- 

 gual mass, binding strongly together the lateral muscles to which 

 they are fastened, and forming at the same time a firm support 

 to the spiny ridge, and a fulcrum ^ it were for the semicircular 

 muscles that rotate it. 



The inner concave aspect of the horny plates which form the 

 lateral walls of the cavity of the mouth is uncovered for about 

 one-third of its extent at the upper and anterior part, PI. I. figs. 6 

 and 8 « «, PI. III. fig. 6 h. The rest of the surface is lined by a 

 thick, strong muscular mass, PI. I. figs. 6_^ and 8 e, and PI. II. 4. 

 PI. III. fig. 6 c, the fibres of which are inserted into nearly the 

 whole of the lower half of its internal aspect, just above the in- 

 sertion of the external lateral muscles of the tongue, with which 

 they are blended. From this attachment the fibres pass obliquely 

 upwards, the inner ones being the longest and inclining forwards, 

 and a thick body of muscle is formed, which is terminated above 

 by a flat and broad border, PI. I. fig.8/and PI. II. 4 h, PL III. ^d, 

 that is free for some distance, lying nearly in contact with the 



