. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 284 REPTILIA. of repose, in which condition it covers them by drawing the inclosing pouch over them. The internal jitcryguid (£), shorter and smaller than the external, runs from the alar bone to the posterior part of the lower jaw, which it consequently draws forwards. The lyifirnn-jijierygqid (1), which has no ana- logue in other vertebrata, arises from the mesial portion of the base of the cranium, and runs outwards and backwards to be at- tached to the inner surface of the pterygoid plate, which it can thus drag forw


. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 284 REPTILIA. of repose, in which condition it covers them by drawing the inclosing pouch over them. The internal jitcryguid (£), shorter and smaller than the external, runs from the alar bone to the posterior part of the lower jaw, which it consequently draws forwards. The lyifirnn-jijierygqid (1), which has no ana- logue in other vertebrata, arises from the mesial portion of the base of the cranium, and runs outwards and backwards to be at- tached to the inner surface of the pterygoid plate, which it can thus drag forwards and inwards so as to cause the protraction of the superior maxillary bone, thus raising the venom fangs; it will likewise narrow the mouth by causing the approximation of the two internal arches. It is assisted in its ac- tion by a muscle, which Cuvier regards as a dismemberment of the temporal, the post-or- bito-palnthic, which runs from the temporal fossa behind the orbit to the palatine arch. rY\\espheno-}iaIatine(fig. 205,«) antagonises the two last ; it extends from all the length of the palatine arch to the mesial line of the base of the cranium ; its direction crossing that of the preceding muscle, above which it is placed. By its contraction it brings back- wards the entire upper jaw, approximating at the same time the branches that form it. Two small muscles (fig. 205, o) advance from beneath the sphenoid, and run close to each other to be inserted by a slender tendon into the vomer. These are the spkeno-vomerine muscles of Duges, for which it would be dif- ficult to find analogues. These muscles de- press the muzzle. In all the true serpents the tongue is en- closed in a membranous sheath, to be de- scribed hereafter ; and the os hyoides, which in the ophidia has no connexion with the larynx, consists of two simple cartilaginous stems (fg. 206, B,) running parallel to each other, which bend forwards underneath the sheath of the tongue, where they unite to form


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