6 MINOT ON THE TONGUE 



«implest known form resembles to a striking extent the disposition I have just described 

 in the snakes. According to the view that the lower jaw is a modified visceral arch, an 

 mportant part of the mandibular muscles must be modifications of the M. constrictor 

 superjicialis ; — a reversion, therefore, seems possible. It must, however, be further 

 assumed, that the longitudinal ventral muscles ^ are also fused with the general muscular 

 layer. I could not satisfy myself that any fibres were attached to the base of the tongue, 

 certainly no fibres enter the tongue itself. I am therefore unable to confirm Duges' 

 statement that there is a distinct muscle homologous with the genio-glossus. 



Underneath (above) the general layer just described, are four distinct pairs of muscles, all 

 of small size. First, the genio-vaginii, running from the front ends of the mandibles to the 

 sides of the sheath, along which they pass on to the attached part of the tongue, 

 extending some distance backwards. A transverse section through the sheath shows 

 that the only muscular fibres it contains belong to these muscles. A section through 

 the base of the tongue shows them lying at the sides, but without connection with the 

 proper lingual muscles. Second, the genio-tracheal, also arising from the mandibles, but 

 further back, and running obliquely backwards and inwards to be inserted into the 

 trachea, some distance behind the glottis. Third, the retractores tracheae, inserted above 

 and in front of the genio-tracheal muscles and running obliquely backwards and 

 outwards. Fourth, the epi-tracheal muscles, short longitudinal bands placed laterally 

 and ventrally upon the trachea, immediately behind the glottis (c/". cut 1). Of 

 these four muscles, the genio-vaginii are the only ones directly concerned vsith the 

 movements of the tongue. 



The sheath of the tongue is lined by a continuation of the buccal epithelium, and has a 

 fibrous tunica -propria. As already mentioned, the only muscles of the sheath are the 

 longitudinal genio-vaginii. 



Transyerse sections which are now to be considered, enable us to study the disposition 

 of the miiscles and tissues of the tongue. 



Such a section, taken a short distance behind the fork of the tongue, at the level of the 

 line 7, in W. 1, fig. 1, is represented in fig. 7. The section is limited by an epithelium, sup- 

 ported by a fibrous submucosa, which is thickest on the upper and lower surfaces, and 

 least developed at the sides, but is nowhere sharply limited against the underlying con- 

 nective tissue. This last is distinctly adenoid, being formed of fibres, so disposed as to 

 make a mesh work of fusiform interspaces ; among the fibres are scattered, first, large 

 numbers of small, round, darkly stained nuclei ; second, a smaller number of paler gran- 

 ular nuclei, three times the size of those first named; third, ramified pigment cells, most 

 numerous dorsally, and sometimes entirely wanting on the ventral surface ; some of these 

 cells appear to send their processes in between the epithelial cells. In parts of some 

 preparations, I have observed around each small nucleus, a clear space, which I consider 

 the cell body, marked off by a distinct outline, which I regard as the cell wall. The cell 

 closely resembles the red blood globules. An irregular granular cell body is sometimes 

 distinctly visible around the larger nuclei. Finally the tissue contains numerous vascular 

 spaces. The adenoid tissue is bounded internally by the common fibrous sheath of the 



' In Selachiaus the coraco-aruales, coraco-liyoidecus and coraco-mandibulare. 



