The cat; an introduction to the study of backboned animals, especially mammals (1881) (20399935739)

Title: The cat; an introduction to the study of backboned animals, especially mammals

Identifier: catintroductiont00miva (find matches)

Year: 1881 (1880s)

Authors: Mivart, St. George Jackson, 1827-1900

Subjects: Cats; Anatomy, Comparative

Publisher: London, Murray

Contributing Library: MBLWHOI Library

Digitizing Sponsor: MBLWHOI Library

Text Appearing Before Image:

CHAP. X.) THE DEVELOPMENT OF THE CAT. 323 grows up around and over the embryo. This up-growth continues until the ascending folds of the circumvallation meet and coalesce ahove the embryo, and so form a completely closed sac above it. This sac is the amnion (Fig. 148, -, '^ ,^). The cavity enclosed by it is, of course, the same as the cavity of the " chamber" above mo U, dl\ Li

Text Appearing After Image:

INITIAL STAGES OP DEVELOPMENT. Fig. 147.âEmbryo seen in Transverse Section, showing formation of Somatopleitre and Splanchnopleure, and of the Peritoneal Cavity. The part of the Somato- pleurb which ascends beyond the embryo is not represented. mg. Medullary groove, e. Ejiiblast. m. Mesoblast. 74. Hypoblast. Id. Lamiiiee dorsales. Iv. Laminfe veutrales. 71. Notochord. lie. Neural canal. sp. Splauchnoiileure. so. Somatopleure. i. Intestine. u. Umbilical vesicle. vfj. Prominences in which primitive urinary and sexual glands arise. J). Peritoneal cavity. me. Mesenterj'. A. Embryo, with the mesoblast as yet unsplit. B. Mesoblast split into somatopleure and splanchnopleure, and â with an incipient separation between the intestine and the subjacent umbilical vesical. C. Further closing oil' of intestine from um- bilical vesicle. D. The body cavity (or peritoneal cavity) com- pletely enclosed by somatopleure, while the part of the splanchnopleure between the intestine and superior part of the embryo has become attenuated into a mesentery (me). mentioned as being " gradually formed between the surface of the embryo" and the " more and more bent over surface" of the ascending circumvallation. The embryo lies in the amnion as in a water-bed. For though at first this sac is very small, it subse- quently enlarges and becomes filled with a certain fluid called the liquor amnii. As the ascending folds are (as before said) double on all sides (Fig. 148, ^) it follows that upon their coalescence a double sac is at first formed. The amnion is the inner of these two sacs. The sac external to it (formed of the outer layers of all the folds) disappears by coalescing with the chorion, or outer envelope of the ovum, within which of course all the changes here described take place (Fig. 148, â ^). As the primitive peritoneal cavity was con- tinuous with the space enclosed between the two layers of tfte ascending folds, it follows that (upon the completion of the amnion) there comes to be for a time a communication (over the back of the embryo and above the amnion) between the two sides of the peri- toneal cavity. This space is occupied by a more or less fluid or gelatinous substance (Fig. 148, 5r). This communication is, how- ever, soon cut off by the descent and in growth of that part of the somatopleure which forms the side-walls of the body of the embryo. Y 2

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