A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . Ca-vnty is a Cleft Between the Trophoblast andFormative Ectoderm, a, .\mniotic cavity; ec, ectoderm; en, endo-derm; tr, trophoblast. (.\fter Hubrecht.) is met with in the shrew, the dog, and the rabbit ()). In this type no cavity is formed in the knob,which simply flattens out to form the embryonal this, the trophoblast persists for a time in therabbit as a very thin covering layer. In the dog(Fig. 0()0) no covering layer is to be found at a veryea
A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . Ca-vnty is a Cleft Between the Trophoblast andFormative Ectoderm, a, .\mniotic cavity; ec, ectoderm; en, endo-derm; tr, trophoblast. (.\fter Hubrecht.) is met with in the shrew, the dog, and the rabbit ()). In this type no cavity is formed in the knob,which simply flattens out to form the embryonal this, the trophoblast persists for a time in therabbit as a very thin covering layer. In the dog(Fig. 0()0) no covering layer is to be found at a veryearly stage. Type I is of special interest because of the modi-fications of it that are found in the rodents and thePrimates. In the mice, rats, and guinea-pig we have 85 Blastoderm REFERENCE HANDBOOK OF THE MEDICAL SCIEXCES the condition known as the inversion of the germ-layers. At one time this condition (Fig. 667) createda great deal of discussion, for what was apparentlyectoderm was found to produce endodermal structuresand i-ice versa. But it is recognized now that wehave in these forms merely an exaggeration of the con-. of Kahbit, Nmety-four Hours after Coitus,inner mass of cells: Z, zona pellucida. (The Fig. 665.—Blastocy£c, Trophoblast; upper half represents an optical section, the lower half a surface \iew.}(.\fter Van Beneden.) ditions seen in such animals as bats, with certainmodifications. This condition is associated with agreat development of the covering layer, which formsthe first organ for the attachment of the embrj-o tothe uterine wall, and has received the name ecto-placenta. The blastocyst as a w-hole becomes cylindrical withthe ectoplacenta (Tr, Fig. 667) at one end. This isgreatly tliickened and projects into the cavity of theblastocyst, pushing the embrj-onal knob before it,forming a central mass which nearly fills the rest of the trophoblast, the parietal portion.
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Keywords: ., bookauthorbuckalbe, bookcentury1900, bookdecade1910, bookyear1913
