. The biology of the amphibia. Amphibians. THE SENSE ORGANS AND THEIR FUNCTIONS 325 the mesial part of the nasal chamber; the expired, through the lateral. The latter region becomes more or less devoid of olfac- tory epithelium, except at one point, where a special sense area develops. This is Jacobson's organ (Fig. 117), and it serves to test the food substances in the mouth. In frogs Jacobson's organ lies in a sac at the anterior mesial corner of the nasal chamber. In urodeles it has usually a lateral position which, in spite of the studies of Wilder (1892), Seydel (1895), and Anton (1908),
. The biology of the amphibia. Amphibians. THE SENSE ORGANS AND THEIR FUNCTIONS 325 the mesial part of the nasal chamber; the expired, through the lateral. The latter region becomes more or less devoid of olfac- tory epithelium, except at one point, where a special sense area develops. This is Jacobson's organ (Fig. 117), and it serves to test the food substances in the mouth. In frogs Jacobson's organ lies in a sac at the anterior mesial corner of the nasal chamber. In urodeles it has usually a lateral position which, in spite of the studies of Wilder (1892), Seydel (1895), and Anton (1908), has caused various investigators to doubt its homology. Fig. 117.—Cross-section of nasal cavity of a tree frog showing Jacobson's organ and the glands associated with the nasal cavity. CP., cartilago para- nasals; , cartilago paraseptalis inferior; , cartilago paraseptalis superior; , cartilago septi; , recessus medialis nasi (ductus Jacobsoni); , ductus nasolacrimal; , ductus olfactorius; , glandula Jacobsoni; , glandula nasalis lateralis; , glandula palacinus; Mx., maxilla; , os nasale; , pars intermedia; , recessus maxillaris. (After Mihalkovics.) with the mouth tester of frogs. The perennibranchs present certain deviations from the larval condition. Siren and Amphi- uma have both developed a modification of the choanal valve which permits its being opened at will (Bruner, 1914a), and both forms which are terrestrial at times, have a well-developed Jacob- son's organ. Cryptobranchus, which represents a partly meta- morphosed type, has lost the choanal valves and developed a Jacobson's organ. This structure arises in the larvae in anticipa- tion of its use after metamorphosis, and hence it is not surprising to find that Siren and Amphiuina with their special valves have. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appeara
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Keywords: ., bookcentury1900, bookpublishernewyorkmcgr, booksubjectamphibians
