. The biology of the amphibia. Amphibians. 172 THE BIOLOGY OF THE AMPHIBIA. strictor. Bruner (1896) has shown that the latter contracts whenever the nostrils are moistened. In the water the nares are closed but most urodeles in this situation resume their larval habits of buccopharyngeal respiration and water is taken in and expelled from the mouth. Apparently the smooth muscle equipment of the external nares was found inadequate for the needs of the Salientia, and they seized upon a unique way of utilizing the quick-moving striated jaw and throat muscles for effecting a closing of the nares.
. The biology of the amphibia. Amphibians. 172 THE BIOLOGY OF THE AMPHIBIA. strictor. Bruner (1896) has shown that the latter contracts whenever the nostrils are moistened. In the water the nares are closed but most urodeles in this situation resume their larval habits of buccopharyngeal respiration and water is taken in and expelled from the mouth. Apparently the smooth muscle equipment of the external nares was found inadequate for the needs of the Salientia, and they seized upon a unique way of utilizing the quick-moving striated jaw and throat muscles for effecting a closing of the nares. A tubercle was formed on the anterior angle of the lower jaw and this, supported by the small mento-Meckelian bones underlying it, was made available as a wedge. When, either by a contraction of the submental muscle or by a slight forward movement of the lower jaw, the tubercle is carried upward, it pushes apart the two premaxillary bones and this in turn effects a closing of the nostrils by carrying mesially the prenasal superior process of the nasal cartilage (Gaupp, 1896). Though rudimentary smooth Fig. 68.—a secondary muscles of the urodele nares are present mechanism for closing the in Salientia, they apparently play no nasal chamber of frogs. ' J j r J Roof of the mouth of Rana part in the occlusion of the nostril (Bruner, escuienta on which is ache- 1902), except in such forms as Xenopus matically projected the <• hyoid and the anterior having fused premaxillaries. end of the omosternum. In both urodeles and Salientia the A process of the hyoid fits into the internal nares rhythmical throat movements of buc- ^After ^wuurn^ raised* copharyngeal respiration are interrupted by a deeper lowering of the throat. At the height of this movement the nares are closed, the glottis opened, and the air streams from the lungs into the buccal cavity. Immediately the throat muscles are vigorously con- tracted and the mixed air is forced back into the lungs through the open glotti
Size: 1672px × 1494px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpublishernewyorkmcgr, booksubjectamphibians
