. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 436 branchial chamber requires altogether too great a readjustment of adjacent structures. Moreover, the facts of development gainsay any such supposition. After the metamorphosis, in young frogs (R. fusca), of about 17 mm length the pseudothyroid is seen as a lymphoid knot pro- jecting into a lymph space, lateral and somewhat posterior to the thyroid gland, and ventral to the processus postero-lateralis of the hyoid cartilage (Fig. 1). The external jugular vein runs along its lateral border, and the greater part of the body
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 436 branchial chamber requires altogether too great a readjustment of adjacent structures. Moreover, the facts of development gainsay any such supposition. After the metamorphosis, in young frogs (R. fusca), of about 17 mm length the pseudothyroid is seen as a lymphoid knot pro- jecting into a lymph space, lateral and somewhat posterior to the thyroid gland, and ventral to the processus postero-lateralis of the hyoid cartilage (Fig. 1). The external jugular vein runs along its lateral border, and the greater part of the body lies anterior to the junction of the latter vein with the pharyngeal vein. The lymph space mentioned is a recess of the sinus lymphaticus sternal is, although at this stage of development it is not uniformly in com- munication with the latter. A communication is sometimes found be- tween the pseudothyroid lymph recess and the sinus parahyoideus. At this time the only vestiges of the gills still persisting are two rudiments on each side, one dorsal to the carotid gland and the second postero-ventral to the aortic arch. The first is a remnant of the dorsal portion of the degenerating gills, while the second comes from a middle region of the gill-remains. Passing from this stage of development when the pseudothyroid first assumes a characteristic lymphoid structure, to a stage shortly after the tail of the tadpole has disappeared, in frogs of 13 mm length, there is seen in the position exactly corresponding to the situation of the pseudothyroid as above described a vascular network, in the meshes of which are degenerating muscle fibres (Figs. 2, 3 and 4). Examination of still earlier stages of development shows that CO prth. dm Fig. 2. Cross-section througli the head of a youug frog ( fuscaj of 13 mm length; parts dorsal to the pharj-nx removed. In the median mass (cp) ventral to the hyoglossus muscle blood vessels are seen developing, extending laterally to the region of the e
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Keywords: ., bookcentury1900, bookdecade1900, bookpublisherjenag, bookyear1902
