. The Cambridge natural history. Zoology. LUNGS—VOICE 47 smaller in comparison than the right, and there is no pulniouarj' vein. The auricular septum has a large aperture, the comnmni- cation between the auricles being larger than even in Nrcturus (which breathes essentially by gills). The sinus venosus, instead of opening into the right auricle only, opens more freely into the left than into the right, and the latter communicates more directly with the ventricle than the left, instead of about equally. In short, the heart of these creatures appears almost bilocular, instead of being trilocula
. The Cambridge natural history. Zoology. LUNGS—VOICE 47 smaller in comparison than the right, and there is no pulniouarj' vein. The auricular septum has a large aperture, the comnmni- cation between the auricles being larger than even in Nrcturus (which breathes essentially by gills). The sinus venosus, instead of opening into the right auricle only, opens more freely into the left than into the right, and the latter communicates more directly with the ventricle than the left, instead of about equally. In short, the heart of these creatures appears almost bilocular, instead of being trilocular, at least functionally. The lungs of the Urodela are always simple, extremely thin- walled bags. They are highly developed in the Anura, the walls being modified into numerous air-cells, whereby the respiratory surface is considerably increased. The lungs are filled with air by the pumping motion of the throat while the mouth is closed, the nostrils being provided with muscular valves. A muscular apparatus assists the filling of the lungs in the Anura.^ Most, if not all, Anura and some Urodela have a voice pro- duced by the larynx, which, especially in the Anura, is provided with a complicated cartilaginous and muscular apparatus and with vocal cords. The voice of the Urodela is at the best a feeble squeak. The females of the Anura are either mute or they produce a mere grunt, but that of many males is very loud, and, moreover, in many species it is intensified by vocal sacs which act as resonators. These sacs are A B diverticula of the lining of pj^ e.—internal view of the moutli of A, the mouth-cavity, and bulge Jic^a esculenta, B, Bufo calamita (cf. Fig. n2, •1. , , p. 269). CA, Choana, or inner nasal opening; out the outer* skm and the ^^ opening of the Eustachian tube; S, slit muscles, chiefly the mylo- l^^^ing into the vocal sac; T, tongue ; To, ' •' •' patches of teeth on the vomers. hyoid, of the throat. The nostrils and the mouth are firmly closed during th
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
