THE ALIMENTARY TRACT, SPLEEN, AND MESENTERIES 263 

 gum. The junction between these two portions is clearly marked. 

 Three tissues combine to form each tooth, namely, dentine, enamel, 

 and cement. These features may all be clearly seen by pulling out 

 a tooth — which is quite easy — and staining it in a solution of 

 alizarin in absolute alcohol and mounting it in balsam on a 

 slide. 



The mandibular and maxillary teeth serve merely to retain the 

 food in the mouth, but the pre-vomerine teeth on the palate assist 

 the tongue to work the food back to the pharynx so that it may be 

 swallowed. 



The tongue of the Salamander is a much less highly developed 

 organ than that of the Frog, and consists simply of an oval pad firmly 

 affixed to the floor of the mouth and with it to the copula of the 

 hyobranchial apparatus. It is free laterally and to some extent pos- 

 teriorly also, but nothing like to the same extent as the Frog's tongue. 

 As Kallius (1901) has shown, the adult structure consists of a secon- 

 dary tongue superimposed on a larval ■primary tongue. The secondary 

 tongue forms practically the whole organ in the adult, and its epithe- 

 lium, which is highly glandular, is thrown into deep folds arranged 

 in a somewhat radial manner, so that the superficial area of the mucous 

 epithelium is enormous. The primary tongue is just visible under the 

 posterior edge of the secondary tongue. It is non-glandular. There 

 is only a slight tendency for the secondary tongue to be bifid 

 posteriorly. The ontogeny of the tongue as described by Kallius 

 (1901) shows that the tongue of Salamandra exhibits a close 

 recapitulation of the changes which Gegenbaur (1894) suggested 

 had taken place during the evolution of this organ in the vertebrate 

 series. 



The mechanism whereby the tongue is extruded from the mouth 

 in the act of seizing food is described on p. 61. 



The epithelium of the mouth and pharynx is glandular and highly 

 vascular, and is of considerable importance in respiration (see also 

 p. 274, etseq.). In addition to this general glandulartissuethereare two 

 specialized sets of glands opening on to the roof of the mouth. These 

 have been described in detail quite recently by Seifert (1932). The 

 first and most important has long been known. It is the glandula 

 intermaxillaris (or internasalis)^ and is situated between the nasal 

 capsules. It discharges by two or three openings into a small median 

 depression lying on the roof of the mouth immediately beneath the 

 gland, and anterior to the pre-vomerine teeth. The other set of 

 specialized glands are the 'Gaumendriise' (Seifert) or glandula pala- 

 tina, which open into a series of grooves on the bases of the 



