. The comparative anatomy of the domesticated animals. Veterinary anatomy. 896 EMBRYOLOGY. placental tufts. It adheres to the internal surface of the uterus. Between the two membranes there is found a small quantity of sanguinolent fluid. The internal face, lined by the external layer of the allantois, is united in the closest manner to that membrane, except at the umbilical cord, where there exists a kind of conical infundibulum occupied by the umbilical vesicle. Structure.—The chorion is a delicate fibrous membrane, traversed by the vascular ramifications of the placenta. It is formed by the
. The comparative anatomy of the domesticated animals. Veterinary anatomy. 896 EMBRYOLOGY. placental tufts. It adheres to the internal surface of the uterus. Between the two membranes there is found a small quantity of sanguinolent fluid. The internal face, lined by the external layer of the allantois, is united in the closest manner to that membrane, except at the umbilical cord, where there exists a kind of conical infundibulum occupied by the umbilical vesicle. Structure.—The chorion is a delicate fibrous membrane, traversed by the vascular ramifications of the placenta. It is formed by the vitelline membrane, to the inner face of which the serous vesicle is applied. It is stated that the zona pellucida, or primitive chorion, as it is called, disappears when the serous vesicle, the definitive chorion, becomes Fig. 423. independent of the amnion. I The chorion is destitute of vessels until the allantois is developed. 2. The Amnion. (Figs. 423, 424.) The second sac enveloping the foetus, the amnion floats freely in the interior of the chorion, to which it is only united at one point through the medium of the umbilical cord. It contains the young creature, which is also attached to its inner face by the vessels of the cord. It is oval in shape, and has thin trans- parent walls. » Its external face is covered by the inner layer of the allantois, to which it adheres slightly. The internal face is perfectly smooth, and is applied more or less directly to the skin of the foetus. It exhales a fluid in which the latter floats— the liquor amnii. Liquor amnii.—Inclosed withf the foetus in the cavity of the amnion, this fluid is more or less abun- dant, according to the period of gestation ; its relative quantity being always less as the foetus is advanced in development. At an early period it is somewhat milky in appearance, but later it assumes a citrine or slightly reddish tint. It has a salt taste, and con- tains 99 per cent of water, with albumen and salts, the p
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