280 THE ALIMENTAEY TRACT, ETC. 



[Smith (/. c.) has, after careful investigation, come to the 

 conclusion that the teeth of It. esculenta and It. temporaria are 

 practically alike, therefore the methods of differentiating 1 the two 

 species by means of the teeth, as given by Leydig, are not to be 

 relied on.] 



(3) The intermaxillary glands (Glandula intermaxillaris) consist 

 of a mass of convoluted tubes, lying chiefly between the pre- 

 maxillary bones and the capsule of the nose, and opening by about 

 twenty to twenty-five ducts at the fore-part of the mouth (Fig. 

 178 ZZ>). A portion of the glands extends high into the nasal 

 cavity (Born), while dorsally another portion lies under the skin 

 and the M. dilatator and M. lateralis narium, which together act as 

 compressors to the subjacent glands : a small, elastic, cartilaginous 

 rod, placed between the anterior margin of the nasal capsule and 

 the under surface of the ascending limb of the premaxilla, opposes 

 these muscles on either side by its spring-like action (Wiedersheim). 



In a fresh skull the openings of the ducts can easily be seen 

 after washing away the mucous secretion ; they are, however, seen 

 to better advantage by treatment with Midler's fluid and subsequent 

 staining with carmine. With sufficient magnifying power, they 

 are then seen as a row of bright dots. The tubules are of uniform 

 thickness, placed closely side by side, and surrounded by a nervous 

 plexus, which contains numerous branching nerve-cells. The epi- 

 thelium of the tubules is cylindrical, with a rounded, finely granular 

 nucleus; processes from the peripheral ends of the cells are con- 

 tinued to a Membrana propria. The ducts are lined with columnar, 

 ciliated epithelium. 



The secretion of the glands is remarkably adhesive, and is wiped 

 off by the tongue when it is projected ,- by this means the tongue 

 becomes a particularly efficacious instrument for capturing prey. 

 The glands are, both histologically and chemically, pure mucous 

 glands. In urodeles the homologous glands are placed in the hollow 

 septum of the nose r between the nasal cavities. 



(4) The tongue (Figs. 179, 182, 183) is a broad, fleshy flap on 

 the floor of the mouth, to which it is attached by the anterior half 

 of its ventral surface as far forwards as the chin. Seen from above 

 it has a wedge-like form, being narrow in front and wider behind, 

 where it is prolonged at each angle to form two cornua. 



By raising the tongue one obtains a view of a portion of the 



