. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 226 Bulletin Museum of Comparative Zoology, Vol. 156, No. 1. Figure 4. Transverse section througli the midtongue of a lizard (Holbrookia texana, Iguanidae). The circular structure in the center is the lingual (entoglossal) process of the hyobranchium, which is surrounded by fibers of the midline intrinsic muscle, musculus (m.) verticalis (V). Dorsal to the verticalis is the m. transversalis (T) and on either side are the paired hyoglossus bundles (H); the lateral part of each bundle is cut off in the figure. Note that
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 226 Bulletin Museum of Comparative Zoology, Vol. 156, No. 1. Figure 4. Transverse section througli the midtongue of a lizard (Holbrookia texana, Iguanidae). The circular structure in the center is the lingual (entoglossal) process of the hyobranchium, which is surrounded by fibers of the midline intrinsic muscle, musculus (m.) verticalis (V). Dorsal to the verticalis is the m. transversalis (T) and on either side are the paired hyoglossus bundles (H); the lateral part of each bundle is cut off in the figure. Note that within each hyoglossus bundle the fibers are separated into two parts: a dense, more vertically oriented dorsolateral portion (1) and a more loosely organized, more longi- tudinally oriented ventromedial portion (2). Scale bar = mm. extrinsic styloglossus fibers. An individual sheet of verticalis occupies a transverse plane across the width of the tongue com- prising a continuum of vertically oriented muscle fibers, yet within a given sheet, a large proportion of the fibers are contrib- uted by a nominally separate muscle, usu- ally from outside the tongue. Further- more, the muscles making this contribu- tion vary along the length of the tongue. Thus, the nominal m. verticalis satisfies neither the definition of "intrinsic," nor even the usual notion of a "; None- theless, the serial coherence of the verti- calis is maintained throughout the med- ullaiy core, despite the disparate sources of its constituent fibers. The Hyoglossus Muscle in Lepidosaurlan Reptiles Lepidosaurs include the tuatara of New Zealand (Sphenoclon) and the squamates, comprising lizards, snakes, and amphisba- enians. The lepidosaurian tongue, with few exceptions, is a highly mobile organ that rivals that of mammals in its internal com- plexity. However, unlike mammals, the principal longitudinal muscles of the tongue lie within its core and not its pe- riphery. These are th
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