Papilla and Nerves of the Tongue of the Frog. 279 



work of it consists of two muscles, the thin and membranous 

 hypoglossus duplex muscle, arising from the lower border 

 ct\ the hyoid bone and advancing upwards and outwards, its 

 fibres expanding in a fan. like shape; and the genioglossus, an 

 impair muscle of a triangular form, whose base is inserted to 

 the apex of the lower jaw-bone, from whence it ascends and 

 joins the inferior surface of the hypoglossus. This last is short 

 and thick, and does not extend beyond the posterior half of 

 the tongue. Numerous transverse fibres of a muscular nature 

 form several layers, and tend to increase the strength of the 

 tongue. As in man, these vessels and nerves are principally 

 situate at the lower surface of the organ, which becomes up- 

 permost in this animal when spread out of the mouth. The 

 upper surface is covered with a very thin membrane, nearly 

 transparent like glass, with all the appearances and properties 

 of cellular tissue. The lowermost, which is the papillary or 

 gustatory surface, is much more thick and opake. 



The surface of the frog's tongue appears to the naked eye 

 nearly smooth and constantly covered with mucus secreted 

 upon it. When forcibly distended, it becomes sufficiently 

 attenuated to allow of the passage of light, and we may then 

 detect very minute elevations over the upper surface. By 

 means of a simple microscope, we find that the apparent even- 

 ness arises merely irom the minuteness of these bodies, and 

 that it contains all the elements of the human tongue, with the 

 exception of the lenticular papillae. Small bodies of a conical, 

 filiform, or cylindrical shape, are seen over the greater part of 

 it, corresponding to the papillae conicse in man. Among these 

 are others, fewer in number, larger, mostly of a globular form, 

 and most abundant towards the extremity of the tongue : 

 these are the fungiform papillae. As in man, they are sup- 

 ported by a kind of neck or pedicel, which is narrower than 

 their free extremity. Sometimes this pedicel disappears, owing 

 frequently to the condition of forcible distension of the mem- 

 brane; the papillathenappears simply globular*. These papillae 

 are those which to the naked eye resemble minute granulations 

 slightly prominent above the rest of the membrane. They 

 diifer from the first-mentioned in another important feature, 

 for they are found to contain a coil of blood-vessels, within 

 which there is a very active circulation. The conical papilloe 

 offer nothing of the sort; numerous vessels ramify among 

 them at their base, without any appearance of permeating 

 witliin them. The simple lens is the best to employ when we 

 tiesire to trace the analogies between the organ in this animal 

 and that of man; but when we wish to examine the papillae 

 * Sec Phil. Mag. vol. xxix. plate 1. 



