| OCR Text |
Show 572 MR. J. B. SUTTON ON THE CRANIAL ARCADE. [Dec. 2, The Palato-pterygoid Arcade. Whilst working over a considerable number of skulls of early human foetuses, I was led to look into the early conditions of the auditory ossicles and the associated branchial bars; in the course of the investigation the following facts came to light. Early in fcetal life, at about the time tbe skull begins to chondrify, there may be seen running from the malleus, and continuous with it, a rod of cartilage which extends downwards to near the extremity of the fronto-nasal cartilage. Its relation to the Meckelian cartilage and the thyroid arch is shown diagrammatically in fig. 2, where a point of considerable importance is illustrated, viz. that the nerve known in human anatomy as the great superficial petrosal or vidian, bears the same morphological relation to the 7th cranial nerve and the superior maxillary branch of the 5th as does the chorda tympani to the 7th and the inferior maxillary division of the 5th (see diagram). To return to the bar of cartilage. Later on in development this bar undergoes metamorphosis, as follows :- (a) The inferior end of the cartilage is ossified and is recognized a. The Chondro-cranium of a human foetus at, the third month, with the associated cartilaginous bars. F.N.P. Fronto-nasal plate. T.T. Tegmen tympani. E.C. Eustachian cartilage. M.C. Meckel's cartilage. S.C. Styloid cartilage. b. The later modification of the arches. 1st arch.-LP. Internal pterygoid palate. E.C. Cartilaginous portion of the Eustachian tubes. Lig. Ant. lig. of the malleus. 2nd arch.-Inf. maxilla, with long internal lateral ligament of the lower jaw. 3rd arcb - Hyoid bone. S.H. Lig. Stylo-hyoid ligament. S.P. Styloid process. 1.11. lympano-hyal and incus. |
