. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 107 coraco-mandibularis muscle and covered on its ventral side by a me- dian portion of the same muscle. The gland varies somewhat in shape and may extend as far forward as the foramen. In a few cases the gland itself appears to be inserted into the foramen. In most cases, however, the connective tissue in- vestment can be traced forward as a strand of tissue distinct from the fasciae of the surrounding muscles, becoming inserted into the foramen as a sort of plug. In no case has there been found any connection between this c
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 107 coraco-mandibularis muscle and covered on its ventral side by a me- dian portion of the same muscle. The gland varies somewhat in shape and may extend as far forward as the foramen. In a few cases the gland itself appears to be inserted into the foramen. In most cases, however, the connective tissue in- vestment can be traced forward as a strand of tissue distinct from the fasciae of the surrounding muscles, becoming inserted into the foramen as a sort of plug. In no case has there been found any connection between this connective tissue and the mucous membrane covering the dorsal surface of the basihyal. Sections have been made of portions of the basihyal cartilages containing the foramina in question. In the case of two examples of S. canicula out of nine examined, and one of S. catulus out of three examined, a very interesting condition has been found. Follicles, identical in appearance and structure with those of the thyroid gland, are present in the connective tissue occupying the foramen (Fig. 4).. c. ty. Fig. 4. Transverse section of basihyal, passing through foramen, of Scyllium canicula X 27. blood vessels, c. cartilage of basihyal. connective tissue plug in foramen, th. fo. thyroid follicles. The occurrence of these follicles in this particular region, and the fact that the connective tissue investment of the thyroid gland only extends as far forward as the foramen and becomes inserted into it, lead me to the conclusion that the latter marks the situation of the anterior end of the original evagination from the ventral wall of the oral cavity; the cartilage of the basihyal having been laid down around it. The foramen corresponds in position with that which I have de- scribed as occurring in the basihyal of Chlamydoselachus which is oc- cupied by the vestige of the thyroid duct. Moreover the thyroid fol- licles which occur in the foramina of these two species of Scyll
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