. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Glandular Field Hyoid ~^4. B Fig. 232. Median section through the floor of the mouth, showing the formation of the glandular tongue, a, Triton alpestris; b, Salamandra maculosa. In the latter the glandular field is encroaching upon the pri- mary tongue to form the secondary tongue. (After Haller.) The lower amphibians, such as the perennibranchiate urodeles, have fishlike tongues of mucous membrane with cartilaginous support. In the higher salamanders the
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Glandular Field Hyoid ~^4. B Fig. 232. Median section through the floor of the mouth, showing the formation of the glandular tongue, a, Triton alpestris; b, Salamandra maculosa. In the latter the glandular field is encroaching upon the pri- mary tongue to form the secondary tongue. (After Haller.) The lower amphibians, such as the perennibranchiate urodeles, have fishlike tongues of mucous membrane with cartilaginous support. In the higher salamanders the horseshoe-shaped groove between the primitive tongue and the lower jaw becomes elevated, particularly in front, into a glandular field (Fig. 232), in which a glutinous mucus, useful in entang- ling captured insects, is secreted. This glandular field gradually rises, thus obliterating the original groove around the under edge of the primary tongue, until finally it becomes incorporated with the latter as an anterior projection, forming the so-called secondary tongue. In the median line at the junction of the primary and secondary tongues, and originally connected with the thyroid gland, there is a tubular down-growth, the thyroglossal duct that persists in mammals as the foramen caecum (Fig. 233). The secondary tongue soon becomes invaded by intrinsic muscles, which greatly increase the range of its movements, and make changes in its shape possible. Of these muscles the genioglossals act as protractors, and the hypoglossals, as retractors. In the American salamander Eurycea, they become so efficient that the sticky tongue may be shot out a considerable distance and retrieved with incredible speed in the capture of insect Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Walter, Herbert Eugene, b. 1867; S
Size: 2696px × 927px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
