158 COMPARATIVE ANATOMY AND PHYSIOLOGY. 



with glands, which are outgrowths of the walls them- 

 selves ; of these the most important and best known 

 are the salivary glands par excellence ; but these 

 are only specially modified forms of the simple 

 tubular, which, with the compound tubular glands, 

 are alone found in the lower Vertebrata, and which 

 have at first no other function than that of lubri- 

 cating the tongue, the mouth cavity, and the food ; 



and they are, 

 therefore, only 

 feebly, if at all, 

 developed in 

 fishes. 



In the Am- 

 phibia the most 

 important is the 

 intermaxillary or 

 internasal gland 

 (Wiedersheim), 

 an idea as to the 

 function of which 



Fig. 71.-Side View and Lo*er Surface of the is to be gathered 

 Tongue of a Gaiago. from the fact that 



in the water- 

 living Axolotl it is but feebly developed, while in 

 the metamorphosed and pulmonate form known 

 as Amblystoma it is of much larger size. In this 

 group, further, where the tongue is so often used 

 as an organ of prehension, the lingual glands are 

 well developed, and their secretion is driven on to the 

 surface of the tongue with every contraction of that 

 organ In the chamseleons, which likewise catch 

 their prey by the aid of their tongue, the labial and 

 palatine glands are well developed ; the median of 

 these latter may be regarded as the homologue of the 

 intermaxillary of the Amphibia. The glands that 

 lie in the floor of the mouth are ordinarily well 



