The development of the human body; a manual of human embryology . Sl ^ p-G cfl ra eu J.^^ > OSHI u in B en o o J! HI*! —y— -. —?—-~-—~~ ?C ,3 en WJuen a § 8 S •d +j .= X .« 3 a1 -^ tnH en S .m en E«5 3 3S ^2 en Sil-23d f^H °-3 a O to <Z s 00n< 8c?d en eflOen • +J tj ceji4 ^_ X 0 z ^_, o ri c t- THE CRANIAL MUSCULATURE. 227 differentiates into the various perineal muscles (Popow-sky). The Cranial Musculature.—As was pointed out in anearlier chapter, the existence of distinct mesodermicsomites has not yet been completely demonstrated inthe head of the human embryo, but in lower form
The development of the human body; a manual of human embryology . Sl ^ p-G cfl ra eu J.^^ > OSHI u in B en o o J! HI*! —y— -. —?—-~-—~~ ?C ,3 en WJuen a § 8 S •d +j .= X .« 3 a1 -^ tnH en S .m en E«5 3 3S ^2 en Sil-23d f^H °-3 a O to <Z s 00n< 8c?d en eflOen • +J tj ceji4 ^_ X 0 z ^_, o ri c t- THE CRANIAL MUSCULATURE. 227 differentiates into the various perineal muscles (Popow-sky). The Cranial Musculature.—As was pointed out in anearlier chapter, the existence of distinct mesodermicsomites has not yet been completely demonstrated inthe head of the human embryo, but in lower forms, such asthe elasmobranch fishes, they are clearly distinguishable,and it may be supposed that their indistinctness in manis a secondary condition. Exactly how many of thesesomites are represented in the mammalian head it is im-. A B Fig. 114.—Perineal Region op Embryos of (A) Two Months and (B)Four to Five Months, showing the Development op the Peri-neal , Nervus dorsalis clitoridis; p, pudendal nerve; sa, sphincter ani;sc, sphincter cloacae; sv, sphincter vaginae.—(Popowsky.) possible to say, but it seems probable, from comparisonwith lower forms, that there is a considerable majority of them, however, early undergo degenera-tion, and in the adult condition only three are recogniz-able, two of which are praeoral in position and one post-oral. The myotomes of the anterior praeoral segmentgive rise to the muscles of the eye supplied by the thirdcranial nerve, those of the posterior one furnish the supe-rior oblique muscles innervated by the fourth nerve, while 228 THE DEVELOPMENT OF THE HUMAN BODY. from the postoral myotomes the external recti, suppliedby the sixth nerve, are developed. The muscles suppliedby the hypoglossal nerve are also derived from myotomes,but they have already be
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
