An introduction to the study of embryology / by Alfred C. Haddon.

  • Alfred Cort Haddon
Date:
1887
Catalogue details

Licence: Public Domain Mark

Credit: An introduction to the study of embryology / by Alfred C. Haddon. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

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    the body-cavity, wliicli become cut off (fig. 150, m.p) by the coming together of the somatic and splanchnic mesoblast. The continuous non-sesmented band of cells connecting the non-segmented muscle- plates with the peritoneal epithelium being known as the inter- mediate cell-mass. Sedgwick found that the passage connecting the body-cavity with that of the muscle-plates persists for some time. Its connection with the ventral dilation of the muscle-plate cavity is carried ventralwards as far as the outer dorsal corner of the segmental duct, so that it appears as a canal opening into the body-cavity just internal to the segmental duct, and thence curling Fia. 176.—Transverse Section through the Trunk of a Duck Embryo with about Twenty-Four Mesoblastio Somites. [From Balfour.] am. amnion : ao. aorta; ca.v. cardinal vein ; cJi. notocborcl; hy. hypoblast ■ m s muscle-plate ; so. soniatopleur; sp. splanchnopleur; sp.c. spinal cord • sv a snin'ai gaughon: st. segmental tube ; icd. Wolffian (segmental) duct. ' round its dorsal wall, opens into the muscle-plate cavity. The ventral wall of this passage is formed of large columnar cells, the inner and dorsal wall of much flatter cells. At the next stage of development the passage becomes quite separated from the muscle-plate cavity, and now lies as a blind tube (fig. 175, St) opening into the body-cavity internal to the segmental duct, with which it soon unites and forms a segmental tubule. ° Sedgwick has also further shown that in the Fowl, in the reo-ion of the body between the twelfth and fifteenth somites inclusive the segmental tubes (Wolffian tubules) have a double oricrin- (i)'